31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

ABFM Family Medicine Certification Study Guide Exam

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1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

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3 Chapter 3: Ethics, Law, Biostatistics & Health Equity

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4 Chapter 4: Lifestyle Counseling & Behavior Change

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6 Chapter 6: Routine Adult Immunizations

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7 Chapter 7: Pediatric Health Maintenance & Surveillance

7.1 Newborn Examination & Early Postnatal Care 7.2 Well-Child Care, Developmental Surveillance & Milestones 7.3 Pediatric & Adolescent Screening: Vision, Hearing, Anemia & Lead 7.4 Pediatric Oral Health, Dental Screening & Fluoride

8 Chapter 8: Behavioral Health & Safety Screening

8.1 Primary Care Depression, Anxiety & Behavioral Health Screening 8.2 Domestic Violence, Intimate Partner Violence & Firearm Safety 8.3 Occupational Health & Recreational Safety Counseling

9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

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10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

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11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

11.1 Colorectal Cancer Screening Modalities & Intervals 11.2 Lung Cancer Screening with Low-Dose CT 11.3 Prostate Cancer Screening & Shared Decision-Making

12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

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13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

13.1 Preconception Planning & Comprehensive Contraception Management 13.2 Lactation Support & Breastfeeding Counseling 13.3 Preoperative Medical Evaluation & Pre-Participation Sports Exam

14 Chapter 14: Emergent Cardiovascular Conditions

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15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

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16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

17.1 Acute Ischemic Stroke & Intracranial Hemorrhage 17.2 Syncope Evaluation & Status Epilepticus 17.3 Acute Delirium, Encephalopathy & Severe Confusion

18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

21.1 Major Trauma Resuscitation & Initial Assessment 21.2 Burn Assessment, Inhalation Injury & Resuscitation 21.3 Laceration Management, Complex Wounds & Animal Bites

22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

25.1 Severe Symptomatic Anemias & Coagulopathic Emergencies 25.2 Testicular Torsion, Priapism & Acute Urinary Retention 25.3 Urgent Odontogenic Infections & Dental Trauma

26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

27.1 Primary Acute Headaches: Migraine, Tension & Cluster 27.2 Concussion & Minor Closed Head Injury Evaluation 27.3 Transient Ischemic Attack Evaluation & ABCD2 Risk Scoring

28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

30.1 Influenza, COVID-19 & Viral Respiratory Syndromes 30.2 Acute Bronchitis & Lower Respiratory Tract Infections 30.3 Ambulatory Community-Acquired Pneumonia

31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

33.1 Peptic Ulcer Disease & Gastritis 33.2 Dysphagia, Esophagitis & Acute Esophageal Disorders 33.3 Acute Nausea, Vomiting & Foodborne Illness

34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

45.1 Uncomplicated UTI, Pyelonephritis & Acute Urethritis 45.2 Hematuria Workup & Glomerulonephritis 45.3 Nephrolithiasis & Acute Urinary Tract Obstruction

46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

Key Takeaways Explain This Topic AI

Idiopathic Pulmonary Fibrosis (IPF) predominantly affects males older than 60 with a history of tobacco use, presenting with insidious exertional dyspnea, nonproductive dry cough, digital clubbing, and hallmark bilateral end-inspiratory bibasilar fine 'velcro' crackles.

High-resolution computed tomography (HRCT) demonstrating a definite Usual Interstitial Pneumonia (UIP) pattern—characterized by subpleural, basal predominance, reticular opacities, traction bronchiectasis, and honeycombing—is diagnostic of IPF and eliminates the need for invasive surgical lung biopsy.

Pulmonary function testing in interstitial lung diseases reveals a restrictive ventilatory defect (TLC <80% predicted, FVC reduced, with a normal or elevated FEV1/FVC ratio >0.70-0.80) accompanied by an early and disproportionately severe reduction in diffusing capacity for carbon monoxide (DLCO <80% predicted).

Antifibrotic pharmacotherapy with pirfenidone or nintedanib slows the rate of FVC decline and disease progression in IPF; early referral for lung transplantation is imperative as IPF carries a median survival of only 3 to 5 years without treatment.

Sarcoidosis is a systemic non-caseating granulomatous disease common in young adults and Black females; acute presentation with Löfgren syndrome (the triad of erythema nodosum, bilateral hilar lymphadenopathy, and migratory periarticular ankle arthritis) carries an >85% spontaneous remission rate and does not require tissue biopsy or immunosuppressive therapy.

Last updated: September 2026

Interstitial Lung Diseases (ILD): Clinical Spectrum & Classification

Interstitial lung disease (ILD)—also termed diffuse parenchymal lung disease (DPLD)—encompasses a heterogeneous group of more than 200 distinct pulmonary disorders characterized by varying degrees of chronic inflammation and progressive fibroblastic proliferation within the alveolar interstitium, alveolar epithelium, and capillary endothelium. This inflammatory and fibrotic remodeling impairs alveolar gas exchange, leading to progressive ventilatory restriction and hypoxemia.

Classification of Interstitial Lung Diseases

ILDs are systematically categorized into four major clinical groups:

ILDs of Known Cause :

Connective Tissue Disease-Associated ILD (CTD-ILD) : Systemic sclerosis (scleroderma), rheumatoid arthritis, systemic lupus erythematosus, polymyositis/dermatomyositis, Sjögren syndrome.

Environmental / Occupational Pneumoconioses : Asbestosis (insulation, shipyard workers; lower lobe plaques and fibrosis), Silicosis (sandblasters, quarry workers; upper lobe nodules with eggshell hilar calcification), Berylliosis (aerospace, nuclear workers).

Drug-Induced ILD : Amiodarone, bleomycin, methotrexate, nitrofurantoin, busulfan, checkpoint inhibitors.

Idiopathic Interstitial Pneumonias (IIP) :

Idiopathic Pulmonary Fibrosis (IPF) : The prototype fibrotic lung disease (UIP histopathologic pattern).

Nonspecific Interstitial Pneumonia (NSIP) : Common in non-smoking middle-aged females and CTD; responsive to corticosteroids.

Cryptogenic Organizing Pneumonia (COP) : Intra-alveolar fibroblastic buds (Masson bodies); dramatic response to oral steroids.

Granulomatous ILD :

Sarcoidosis : Multisystem non-caseating granulomatous disease.

Hypersensitivity Pneumonitis (HP) : Immunologic response to inhaled organic antigens.

Rare / Miscellaneous ILDs :

Lymphangioleiomyomatosis (LAM), Pulmonary Langerhans Cell Histiocytosis (PLCH), Eosinophilic pneumonia.

Idiopathic Pulmonary Fibrosis (IPF): Pathogenesis, Diagnosis & Antifibrotic Therapy

Idiopathic Pulmonary Fibrosis is a specific form of chronic, progressive, fibrosing interstitial pneumonia of unknown cause, occurring primarily in older adults, limited to the lungs, and characterized histopathologically and radiologically by the Usual Interstitial Pneumonia (UIP) pattern.

Epidemiology & Pathogenetic Mechanics

Demographics : IPF is predominantly a disease of older males (male-to-female ratio ~2:1), rarely diagnosed before age 55 (peak incidence 65-75 years) . Over 70% of affected patients have a substantial history of cigarette smoking (>20 pack-years) .

Pathogenesis : IPF is no longer considered an inflammatory disease. Rather, it is driven by repetitive micro-injuries to an aging, genetically susceptible alveolar epithelium (mutations in telomerase genes TERT and TERC , or surfactant proteins SFTPC , and MUC5B promoter polymorphism).

Injured alveolar type II epithelial cells undergo premature senescence and apoptosis, releasing excessive pro-fibrotic mediators, predominantly Transforming Growth Factor-beta 1 (TGF-β1) and Platelet-Derived Growth Factor (PDGF) .

These cytokines stimulate the persistent activation and proliferation of fibroblasts into fibroblastic foci , driving unregulated deposition of dense collagenous extracellular matrix, irreversible architectural destruction, and microscopic subpleural cystic transformation ( honeycombing ). PATHOGENETIC SEQUENCE OF IDIOPATHIC PULMONARY FIBROSIS

• Aging / Smoking / Genetic Susceptibility (MUC5B, TERT/TERC)
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• Repetitive Alveolar Type II Epithelial Micro-injury
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• Aberrant Wound Healing & Senescence (Failure of Re-epithelialization)
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• Unregulated TGF-β1, PDGF & VEGF Release
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• Myofibroblast Proliferation & Collagen Matrix Deposition (Fibroblastic Foci)
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• Extensive Architectural Distortion, Traction Bronchiectasis & Honeycombing
• Clinical Presentation & Physical Examination

Symptoms : Insidious, slowly progressive exertional dyspnea developing over months to years, frequently accompanied by a persistent, dry, hacking, nonproductive cough that is refractory to antitussive agents. Constitutional symptoms (fever, weight loss) are distinctly absent.

Physical Examination Findings :

Bilateral End-Inspiratory Fine Crackles ('Velcro Crackles') : Heard prominently at the lung bases posteriorly, persisting after coughing. Present in >85% of patients at diagnosis; auscultation sounds remarkably like separating two strips of Velcro fasteners.

Digital Clubbing : Focal enlargement of the terminal phalanges with loss of the normal Lovibond angle (>180°) between the nail bed and nail plate; present in 30% to 50% of patients.

Signs of Cor Pulmonale (Late Disease) : Accentuated pulmonic component of S2 (P2), elevated jugular venous pressure, right ventricular heave, tricuspid regurgitation murmur, and dependent peripheral edema indicate secondary pulmonary hypertension.

• Diagnostic Evaluation: HRCT and Pulmonary Function Testing
• 1. High-Resolution CT (HRCT) of the Chest: The UIP Pattern

Thin-slice (≤1.5 mm) non-contrast chest CT with volumetric inspiratory and expiratory images is the definitive imaging examination. The Definite Usual Interstitial Pneumonia (UIP) pattern is characterized by four cardinal criteria:

Subpleural and Basal Predominance : Changes are maximal immediately adjacent to the visceral pleura and at the lung bases, sparing the apex.

Reticular Abnormalities : Thickened intralobular and interlobular septa producing a coarse net-like appearance.

Traction Bronchiectasis and Bronchiolectasis : Irregular, non-tapering dilation of bronchi and bronchioles dragged open by the elastic recoil of surrounding contracted fibrotic tissue.

Honeycombing : Clustered, subpleural, thick-walled (1-3 mm), cystic airspaces ranging from 3 to 10 mm in diameter, typically arranged in multiple contiguous layers immediately beneath the pleural surface.

High-Yield Board Pearl : The presence of definite honeycombing on HRCT in a patient with a compatible clinical presentation is diagnostic of IPF and eliminates the need for invasive surgical lung biopsy .

2. Pulmonary Function Tests (PFTs): Restrictive Physiology

Spirometry & Lung Volumes :

Forced Vital Capacity (FVC) : Markedly reduced (<80% of predicted).

Forced Expiratory Volume in 1 second (FEV1) : Proportionately reduced.

FEV1/FVC Ratio : Normal or elevated (typically >0.70 to 0.85) due to increased lung radial traction that keeps airways open during expiration.

Total Lung Capacity (TLC) : Confirms true restriction when reduced to <80% of predicted .

Diffusing Capacity of the Lung for Carbon Monoxide (DLCO) :

Markedly and disproportionately reduced (<80% predicted, often <50%) , reflecting the loss of functional alveolar-capillary membrane surface area and microvascular destruction.

Severe desaturation during the 6-minute walk test (6MWT; SpO2 falling below 88%) is a powerful independent predictor of mortality.

Evidence-Based Management of IPF IPF PHARMACOTHERAPY & MANAGEMENT SUMMARY

• CONFIRMED IPF DIAGNOSIS (UIP Pattern on HRCT, Excluded Secondary Causes)
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• ANTIFIBROTIC PHARMACOTHERAPY COMPREHENSIVE SUPPORTIVE CARE
• Nintedanib 150 mg PO BID • Early Lung Transplant Referral
• (Tyrosine Kinase Inhibitor; (Median survival 3-5 years)
• Adverse: Diarrhea, LFT elevation) • Supplemental O2 if SpO2 <=88%
• Pirfenidone 801 mg PO TID • Pulmonary Rehabilitation
• (TGF-beta Inhibitor; • Influenza, Pneumococcal, COVID-19
• Adverse: Photosensitivity, Nausea) Vaccinations
• STRICTLY AVOID IMMUNOSUPPRESSION
• (Prednisone/Azathioprine Harmful!)

The Immunosuppression Caution (The PANTHER-IPF Trial) : Historically, clinicians treated IPF with systemic steroids and azathioprine. The landmark NIH-sponsored PANTHER trial (2012) demonstrated that the combination of prednisone + azathioprine + N-acetylcysteine resulted in significantly increased mortality and hospitalizations compared to placebo. Systemic corticosteroids and traditional immunosuppressants are strictly contraindicated in IPF!

FDA-Approved Antifibrotic Agents :

Nintedanib (OFEV) : An intracellular small-molecule tyrosine kinase inhibitor targeting platelet-derived growth factor receptor (PDGFR), fibroblast growth factor receptor (FGFR), and vascular endothelial growth factor receptor (VEGFR). Dosed at 150 mg PO twice daily with food.

Adverse Effects : Diarrhea (occurs in >60% of patients; managed with loperamide and dose reduction to 100 mg BID) and hepatotoxicity (requires monthly liver function test monitoring for the first 3 months, then quarterly).

Pirfenidone (Esbriet) : An oral synthetic pyridone compound that exerts antifibrotic, anti-inflammatory, and antioxidant effects by directly downregulating TGF-β1 and collagen synthesis . Titrated over 3 weeks to a maintenance dose of 801 mg PO three times daily with meals.

Adverse Effects : Severe photosensitivity rash (mandates strict daily use of broad-spectrum SPF 50+ sunscreen and protective clothing), nausea, dyspepsia, anorexia, and elevated hepatic transaminases.

Therapeutic Impact : Both pirfenidone and nintedanib reduce the annual rate of FVC decline by approximately 50% (~100-120 mL/year preserved) and reduce acute exacerbation risk, but neither reverses existing fibrosis.

Definitive Therapy: Lung Transplantation :

IPF carries a grim prognosis with a median survival of only 3 to 5 years from diagnosis without transplantation.

All eligible patients should be referred for lung transplant evaluation at the time of initial diagnosis , regardless of whether their PFTs appear mildly impaired.

Hypersensitivity Pneumonitis (Extrinsic Allergic Alveolitis)

Hypersensitivity pneumonitis (HP) is an immunologically mediated inflammatory and fibrotic lung disease resulting from repeated inhalation of specific environmental organic antigens or low-molecular-weight chemical haptens in sensitized individuals.

Classic Etiologies and Antigens

Bird Fancier's / Pigeon Breeder's Lung : Inhalation of avian proteins (shed antigens from bird droppings, bloom on feathers, parakeets, pigeons, ducks, down bedding/comforters).

Farmer's Lung : Inhalation of thermophilic actinomycetes ( Saccharopolyspora rectivirgula , Thermoactinomyces vulgaris ) colonizing moldy hay, straw, or grain stored at high humidity.

Humidifier / Hot Tub Lung : Aerosolized non-tuberculous mycobacteria ( Mycobacterium avium complex) or molds from contaminated residential ultrasonic humidifiers, hot tubs, or heating/ventilation systems.

Immunopathology & Diagnostic Distinctions

Pathogenesis : Combined Type III (immune complex / IgG-mediated) and Type IV (delayed-type / cell-mediated Th1 and Th17) hypersensitivity reactions leading to lymphocytic infiltration of the alveolar walls and interstitial non-necrotizing, poorly formed granulomas.

Clinical Presentation :

Non-Fibrotic (Acute/Subacute) HP : Episodes of fever, chills, dyspnea, dry cough, and malaise developing 4 to 8 hours following heavy antigen exposure , spontaneously resolving within 24 to 48 hours upon cessation of exposure.

Fibrotic (Chronic) HP : Insidious exertional dyspnea, fatigue, weight loss, and digital clubbing, mimicking IPF.

Diagnostic Findings :

HRCT : Characterized by an upper- and mid-lung predominance (sparing the extreme lung bases), diffuse centrilobular ground-glass opacities, poorly defined centrilobular nodules, and mosaic attenuation due to expiratory air trapping. The combination of ground-glass, normal lung, and air-trapping produces the classic 'three-density pattern' (headcheese sign) .

Bronchoalveolar Lavage (BAL) : Demonstrates marked lymphocytosis (typically >50% lymphocytes) with a decreased CD4:CD8 T-cell ratio (<1.0).

Management : The single most effective and disease-arresting intervention is complete antigen avoidance (removing birds, discarding down comforters, remediating water damage). For acute severe exacerbations, a tapering course of oral prednisone (0.5-1 mg/kg/day over 4 to 8 weeks) accelerates functional recovery.

Sarcoidosis: Clinical Presentation, Staging & Management

Sarcoidosis is a systemic inflammatory disease of unknown etiology characterized pathologically by the accumulation of well-formed, non-caseating (non-necrotizing) epithelioid granulomas in affected tissues, with pulmonary and intrathoracic lymph node involvement occurring in >90% of patients.

Epidemiology & Pathogenesis

Demographics : Highest prevalence in the United States occurs among Black Americans (incidence 3 to 4 times higher than white individuals, with a lifetime risk of ~2.4%) , who often experience more severe, progressive, and extrapulmonary disease. A second peak occurs in individuals of Scandinavian descent. Peak incidence is between 20 and 40 years of age , with a slight female predominance.

Immunopathogenesis : Genetically predisposed hosts (HLA-DRB1 variants) mount an exaggerated antigen-driven Th1-polarized cellular immune response to an unknown environmental trigger. Activated CD4+ T-helper cells and alveolar macrophages release interferon-gamma (IFN-γ), interleukin-2 (IL-2), and TNF-alpha, orchestrating the aggregation of epithelioid histiocytes and multinucleated Langhans giant cells surrounded by a rim of CD4+ T lymphocytes into compact, non-caseating granulomas.

Chest Radiographic Staging (Scadding Criteria)

Thoracic sarcoidosis is classified into five radiographic stages, which correlate strongly with clinical prognosis:

• Stage Radiographic Features Frequency at Diagnosis Spontaneous Remission Rate
• Stage 0 Normal chest radiograph (extrapulmonary sarcoidosis) 5% to 10% Variable

Stage I Bilateral hilar lymphadenopathy (BHL) alone ± right paratracheal adenopathy; clear lung parenchyma 50% 60% to 85% (Excellent prognosis)

Stage II Bilateral hilar lymphadenopathy PLUS diffuse parenchymal infiltrates (reticulonodular opacities, mid/upper zones) 25% to 30% 50% to 60%

Stage III Diffuse parenchymal infiltrates WITHOUT hilar adenopathy (lymphadenopathy has regressed) 10% to 15% 20% to 30%

Stage IV End-stage pulmonary fibrosis : honeycombing, volume loss, traction bronchiectasis, upper lobe hilar retraction 5% 0% (Permanent / Irreversible)

Extrapulmonary Manifestations & Classical Eponyms

Sarcoidosis can affect virtually any organ system, creating diverse clinical presentations: KEY EPONYMIC SYNDROMES IN SARCOIDOSIS

• ┌───────────────────────────────────────────────────────────┐
• │ LÖFGREN SYNDROME │
• │ 1. Erythema Nodosum (tender red shins) │
• │ 2. Bilateral Hilar Lymphadenopathy on CXR │
• │ 3. Migratory Polyarthritis (bilateral symmetric ankles) │
• │ • PROGNOSIS: >85% spontaneous remission within 1-2 years │
• │ • MANAGEMENT: Supportive (NSAIDs); BIOPSY NOT REQUIRED! │
• └───────────────────────────────────────────────────────────┘

• ┌───────────────────────────────────────────────────────────┐
• │ HEERFORDT SYNDROME │
• │ (Uveoparotid Fever) │
• │ 1. Anterior Uveitis │
• │ 2. Parotid Gland Enlargement (bilateral, painless) │
• │ 3. Facial Nerve Palsy (Lower Motor Neuron CN VII) │
• │ 4. Low-Grade Fever │
• │ • MANAGEMENT: Systemic Oral Corticosteroids │
• └───────────────────────────────────────────────────────────┘
• 1. Löfgren Syndrome (High-Yield Board Concept)

An acute, benign presentation defined by the classic clinical triad:

Erythema Nodosum : Painful, tender, erythematous-to-violaceous subcutaneous nodules on the anterior lower legs (shins).

Bilateral Hilar Lymphadenopathy (BHL) on chest radiograph.

Migratory Polyarthritis / Periarthritis : Most commonly involving both ankles symmetrically, often accompanied by marked periarticular swelling.

Crucial Board Rule : Löfgren syndrome has a diagnostic specificity >95%. It runs a self-limiting course with >85% spontaneous remission within 12 to 24 months. Invasive tissue biopsy is strictly unnecessary , and systemic corticosteroids are avoided unless severe pain is unresponsive to oral NSAIDs.

2. Heerfordt Syndrome (Uveoparotid Fever)

A rare acute subacute variant characterized by anterior uveitis, bilateral painless parotid gland tumefaction, peripheral facial nerve (CN VII) palsy, and low-grade pyrexia .

3. Organ-Specific Involvement

Ocular Sarcoidosis (25-50%) : Granulomatous anterior uveitis (blurred vision, eye pain, photophobia, ciliary flush, keratic precipitates) or posterior uveitis/retinal vasculitis. Every patient diagnosed with sarcoidosis must undergo a baseline ophthalmologic slit-lamp examination , because silent uveitis leads to posterior synechiae, secondary glaucoma, and blindness.

Cutaneous Sarcoidosis (25%) :

Erythema Nodosum : Indicates acute disease with good prognosis.

Lupus Pernio : Chronic, indurated, violaceous or purplish-red plaques and nodular lesions distributed across the nose, cheeks, lips, and ears . Pathognomonic for sarcoidosis; strongly correlates with chronic, refractory fibrotic pulmonary disease and upper respiratory tract granulomas.

Cardiac Sarcoidosis (5% to 10% clinical, up to 25% autopsy) : Granulomatous myocardial infiltration causing complete atrioventricular (AV) block, bundle branch blocks, ventricular tachycardia, congestive cardiomyopathy, and sudden cardiac death . Screen all patients with a 12-lead ECG. Confirmation requires cardiac MRI (demonstrating patchy late gadolinium enhancement) or 18F-fluorodeoxyglucose (FDG) cardiac PET. Primary prevention implantable cardioverter-defibrillator (ICD) placement is frequently required.

Neurosarcoidosis (5%) : Cranial mononeuropathies—particularly unilateral or bilateral lower motor neuron facial nerve (CN VII) palsy —are the most common manifestation, followed by basilar meningitis, sensory-motor neuropathy, and hypothalamic-pituitary granulomas causing diabetes insipidus or hyperprolactinemia.

Calcium Metabolism in Sarcoidosis: The 1-Alpha-Hydroxylase Mechanism

Abnormal calcium metabolism occurs in up to 30% of sarcoidosis patients (hypercalciuria is three times more frequent than hypercalcemia, causing nephrolithiasis and nephrocalcinosis): MECHANISM OF HYPERCALCEMIA IN SARCOIDOSIS

• Epithelioid Alveolar Macrophages within Granulomas
• │
• ▼
• CONSTITUTIVE EXPRESSION OF 1-ALPHA-HYDROXYLASE
• (Enzyme lacks feedback inhibition by Calcium or PTH)
• │
• ▼
• Excess Conversion: 25(OH)D3 ───> 1,25(OH)2D3 (Calcitriol)
• │
• ▼
• Increased Intestinal Calcium Absorption & Bone Resorption
• │
• ▼
• ─────────────────────────────────────────────────────────────

LABORATORY PROFILE:

• Serum Calcium: ELEVATED
• Intact Parathyroid Hormone (PTH): SUPPRESSED (<10 pg/mL)
• 25-Hydroxyvitamin D [25(OH)D]: NORMAL or LOW
• 1,25-Dihydroxyvitamin D [1,25(OH)2D]: MARKEDLY ELEVATED
• 24-Hour Urine Calcium: ELEVATED (>300 mg/24h)
• ─────────────────────────────────────────────────────────────

Epithelioid histiocytes and activated macrophages within granulomas autonomously express 1-alpha-hydroxylase , which converts inactive 25-hydroxyvitamin D [calcidiol] to active 1,25-dihydroxyvitamin D [calcitriol] .

Unlike renal 1-alpha-hydroxylase, the macrophage enzyme is not regulated by parathyroid hormone (PTH) and lacks negative feedback inhibition by elevated calcium .

Excessive calcitriol stimulates hyperabsorption of calcium in the small intestine and increases osteoclastic bone resorption, resulting in hypercalcemia with appropriately suppressed intact PTH .

• Diagnostic Strategy & Stepwise Treatment of Sarcoidosis
• Diagnostic Confirmation

Establishing the diagnosis of sarcoidosis requires three pillars:

• A compatible clinical and radiographic presentation;
• Histopathologic documentation of well-formed, non-caseating epithelioid cell granulomas in one or more organs;

Rigorous exclusion of alternative causes of granulomatous disease, particularly tuberculosis (acid-fast bacilli stain and mycobacterial culture) , endemic fungi ( Histoplasma , Coccidioides , Blastomyces via silver stains), and occupational exposures (berylliosis).

Biopsy Strategy : Always biopsy the most accessible, minimally invasive abnormal tissue (e.g., cutaneous plaques or nodules, peripheral lymph nodes, conjunctiva). Do not biopsy erythema nodosum , as it shows non-specific septal panniculitis without granulomas. When superficial sites are absent, bronchoscopy with endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of intrathoracic lymph nodes achieves diagnostic yields >90%.

Serum ACE Level : Elevated in approximately 60% of patients due to synthesis by granuloma epithelioid cells; however, it has poor diagnostic sensitivity and specificity and is not used as a standalone diagnostic test.

Stepwise Treatment Algorithm

Stage I Asymptomatic Sarcoidosis : NO TREATMENT . Observation with serial CXR and PFTs every 6 to 12 months, as >80% undergo spontaneous remission.

Indications for Systemic Pharmacotherapy :

Debilitating or progressively worsening pulmonary symptoms with deteriorating PFTs (decline in FVC ≥10% or DLCO ≥15%);

• Cardiac sarcoidosis (high risk of lethal arrhythmia);
• Neurosarcoidosis;
• Ocular sarcoidosis refractory to topical corticosteroid drops;
• Persistent hypercalcemia or nephrocalcinosis;

Disfiguring cutaneous lesions (lupus pernio).

First-Line Therapy: Systemic Oral Corticosteroids :

Prednisone 20 to 40 mg PO daily for 1 to 3 months, evaluating for symptomatic and radiographic response.

If clinical response is achieved, taper slowly over 6 to 12 months to a target maintenance dose of ≤5 to 10 mg daily, or discontinue.

Second-Line (Steroid-Sparing) Immunosuppression :

Indicated for failure to respond to steroids, intolerable steroid toxicities (diabetes, severe osteoporosis, psychosis), or inability to taper prednisone below 10 mg daily.

Methotrexate (10 to 20 mg PO or SC once weekly) with daily folic acid (1 mg) is the preferred first-line steroid-sparing agent (monitor CBC, LFTs, and renal function).

Alternative second-line agents include azathioprine (1.5-2 mg/kg/day) or leflunomide.

Third-Line Biologic Therapy :

TNF-alpha inhibitors, specifically Infliximab (monoclonal antibody against TNF-α; 3-5 mg/kg IV at weeks 0, 2, 6, then every 4-8 weeks) or Adalimumab .

Highly effective for refractory lupus pernio, severe neurosarcoidosis, and cardiac sarcoidosis resistant to conventional agents.

Loading diagram... Clinical & Radiologic Differentiation of Interstitial Lung Diseases