12.2 Acne, Rosacea & Cutaneous Infections

ABIM Internal Medicine Exam

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1 Chapter 0: The ABIM Exam, Blueprint & Study Strategy

0.1 Exam Format, Question Types & the 2026 Blueprint 0.2 Eligibility, Registration, Fees & Exam-Day Logistics 0.3 Scoring, the Passing Standard & Score Reports 0.4 Building a Blueprint-Weighted Study Plan

2 Chapter 1: Cardiovascular Disease (14% of Exam)

1.1 Ischemic Heart Disease & Acute Coronary Syndromes 1.2 Antithrombotic Therapy, Secondary Prevention & Mechanical Complications of MI 1.3 Atrial Fibrillation, Atrial Flutter & Stroke Prevention 1.4 Supraventricular Tachycardias, Ventricular Arrhythmias & Bradycardias 1.5 Heart Failure: Classification, Staging & Guideline-Directed Medical Therapy 1.6 Device Therapy, HFpEF & the Cardiomyopathies 1.7 Valvular Heart Disease & Endocarditis Prophylaxis 1.8 Pericardial Disease & Acute Aortic Syndromes 1.9 Hypertension: Classification, Diagnosis & Secondary Causes 1.10 Hypertensive Crises & Dyslipidemia 1.11 Adult Congenital Heart Disease & Coarctation of the Aorta 1.12 Syncope: Reflex, Orthostatic & Cardiac Causes 1.13 Cardiac Physical Examination, Murmurs & Antithrombotic Selection

3 Chapter 2: Endocrinology, Diabetes & Metabolism (9% of Exam)

2.1 Diabetes Mellitus: Diagnosis, Glycemic Targets & Pharmacotherapy 2.2 Insulin Therapy, Hyperglycemic Emergencies & Chronic Complications 2.3 Thyroid Function Testing & Hypothyroidism 2.4 Thyrotoxicosis, Thyroid Storm & Thyroid Nodules 2.5 Adrenal & Pituitary Disorders 2.6 Hypercalcemia, Hypocalcemia & Disorders of Mineral Metabolism 2.7 Osteoporosis & Paget Disease of Bone 2.8 Ovarian, Testicular & Reproductive Endocrine Disorders 2.9 Hypoglycemia, Endocrine Tumors, Polyglandular Syndromes & Severe Hypertriglyceridemia

4 Chapter 3: Gastroenterology & Hepatology (9% of Exam)

3.1 Esophageal Disease 3.2 Stomach & Duodenal Disease and Gastrointestinal Hemorrhage 3.3 Inflammatory Bowel Disease 3.4 Celiac Disease & Irritable Bowel Syndrome 3.5 Diverticular Disease & Colorectal Cancer Screening 3.6 Viral Hepatitis, Steatotic & Alcohol-Associated Liver Disease 3.7 Cirrhosis & the Complications of Portal Hypertension 3.8 Acute Pancreatitis 3.9 Chronic Pancreatitis & Biliary Tract Disease 3.10 Inherited, Autoimmune & Drug-Induced Liver Disease 3.11 Small Intestinal Disease, Ischemia & Gastrointestinal Complications of HIV

5 Chapter 4: Infectious Disease (9% of Exam)

4.1 Lower Respiratory Tract Infections & Sepsis Syndromes 4.2 Viral Respiratory Pathogens & Tuberculosis 4.3 Central Nervous System Infections 4.4 Skin, Soft Tissue, Bone & Joint Infections 4.5 Infective Endocarditis & Cardiovascular Infection 4.6 Clostridioides difficile & Catheter-Related Bloodstream Infection 4.7 HIV Diagnosis, Antiretroviral Therapy & Prevention 4.8 Opportunistic Infections & Sexually Transmitted Infections 4.9 Fever of Unknown Origin, Neutropenic Fever & Toxic Shock 4.10 Travel-Related Illness, Vector-Borne Disease & Outbreaks 4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis 4.12 Rheumatic Fever, Poststreptococcal Disease, Enteric & Hepatic Infections

6 Chapter 5: Pulmonary Disease (9% of Exam)

5.1 COPD: Diagnosis, GOLD Classification & Initial Pharmacotherapy 5.2 Interventions That Reduce COPD Mortality & Exacerbation Management 5.3 Asthma: Diagnosis, Stepwise Therapy & Status Asthmaticus 5.4 Interstitial Lung Disease & Idiopathic Pulmonary Fibrosis 5.5 Sarcoidosis, Hypersensitivity Pneumonitis & Occupational Lung Disease 5.6 Pulmonary Embolism: Diagnosis, Risk Stratification & Anticoagulation 5.7 Pulmonary Hypertension & Sleep-Disordered Breathing 5.8 Acute Respiratory Distress Syndrome & Mechanical Ventilation 5.9 Pleural Disease, Empyema & Pneumothorax 5.10 Bronchiectasis, Cystic Fibrosis & Restrictive Lung Disease 5.11 Evaluation of Cough, Dyspnea, Hemoptysis & the Solitary Pulmonary Nodule

7 Chapter 6: Rheumatology & Orthopedics (9% of Exam)

6.1 Rheumatoid Arthritis: Diagnosis & Systemic Manifestations 6.2 Antirheumatic Pharmacotherapy & the Spondyloarthropathies 6.3 Gout: Pathophysiology & Acute Management 6.4 Urate-Lowering Therapy & Calcium Pyrophosphate Deposition Disease 6.5 Osteoarthritis 6.6 Systemic Lupus Erythematosus 6.7 Systemic Sclerosis, Sjogren Syndrome & Inflammatory Myopathies 6.8 The Vasculitides 6.9 Regional Musculoskeletal Syndromes, Back Pain & Sports Injuries 6.10 Other Primary Rheumatic Disorders & Mixed Connective Tissue Disease 6.11 Osteonecrosis & Metabolic Bone Disease

8 Chapter 7: Hematology (6% of Exam)

7.1 Approach to Anemia & the Microcytic Anemias 7.2 Macrocytic, Normocytic & Hemolytic Anemias 7.3 Hemoglobinopathies, Thalassemias & Paroxysmal Nocturnal Hemoglobinuria 7.4 Platelet Disorders, Thrombocytopenia & the Bleeding Patient 7.5 Coagulation Factor Disorders, Thrombophilia & Anticoagulant Reversal 7.6 Acute Leukemias, Chronic Leukemias & Myeloproliferative Neoplasms 7.7 Lymphomas & Plasma Cell Disorders 7.8 Myelodysplastic Syndrome, Myeloproliferative Neoplasms & Porphyria 7.9 Transfusion Medicine & Late Complications of Transplantation

9 Chapter 8: Medical Oncology (6% of Exam)

8.1 Breast, Lung, Colorectal & Prostate Cancer 8.2 Oncologic Emergencies 8.3 Genitourinary & Gynecologic Malignancies 8.4 Head and Neck, Bone & Soft Tissue Cancer and Cancer of Unknown Primary 8.5 Complications of Cancer & Its Treatment 8.6 Cancer Prevention, Survivorship & Psychosocial Care

10 Chapter 9: Nephrology & Urology (6% of Exam)

9.1 Acute Kidney Injury: Staging, Etiology & Urine Microscopy 9.2 Glomerular Disorders & Nephrotic Syndrome 9.3 Nephritic Syndromes, RPGN & Indications for Renal Replacement Therapy 9.4 Chronic Kidney Disease: Staging & Progression Retardation 9.5 Complications of Chronic Kidney Disease: Anemia, CKD-MBD & Acidosis 9.6 Hyponatremia, Hypernatremia & Water Balance 9.7 Potassium Disorders & Systematic Acid-Base Analysis 9.8 Renal Tubular Acidosis & Nephrolithiasis 9.9 Prostate Disorders, Urinary Incontinence & Other Urologic Conditions 9.10 Cystic Kidney Disease, Obstructive Uropathy, Tubulointerstitial Disease & Hematuria

11 Chapter 10: Neurology (4% of Exam)

10.1 Acute Ischemic Stroke: Syndromes & Reperfusion 10.2 Transient Ischemic Attack, Secondary Prevention & Hemorrhagic Stroke 10.3 Headache & Facial Pain 10.4 Seizures, Epilepsy & Movement Disorders 10.5 Multiple Sclerosis & Neuromuscular Junction Disorders 10.6 Motor Neuron Disease & Acute Peripheral Neuropathy 10.7 Cranial Neuropathies & Neuro-Ophthalmology 10.8 Peripheral Neuropathies, CNS Tumors & Other Neurologic Disorders

12 Chapter 11: Psychiatry & Behavioral Health (4% of Exam)

11.1 Major Depressive Disorder & Medical Mimics 11.2 Antidepressant Pharmacotherapy & Treatment-Resistant Depression 11.3 Bipolar Disorder, Mood Stabilizers & Lithium Toxicity 11.4 Anxiety, Stress-Related & Obsessive-Compulsive Disorders 11.5 Alcohol Use Disorder & Withdrawal 11.6 Pharmacotherapy for Alcohol & Opioid Use Disorder 11.7 Toxidromes, Psychiatric Emergencies & Suicide Risk Assessment 11.8 Psychotic, Somatic Symptom, Factitious & Personality Disorders 11.9 Eating Disorders, Sleep Disorders & Sexual Health

13 Chapter 12: Dermatology (3% of Exam)

12.1 Dermatitis, Papulosquamous & Inflammatory Dermatoses 12.2 Acne, Rosacea & Cutaneous Infections 12.3 Herpes Zoster & Autoimmune Blistering Diseases 12.4 Nodules, Tumors & Cutaneous Oncology 12.5 Dermatologic Emergencies & Severe Cutaneous Adverse Reactions 12.6 Pigment Disorders, Alopecia, Nail Disease & Photosensitivity 12.7 Vascular Dermatoses, Environmental Injury & Cutaneous Signs of Systemic Disease

14 Chapter 13: Obstetrics & Gynecology / Women's Health (3% of Exam)

13.1 Contraception, Preconception Care & Teratogenicity 13.2 Hypertensive Disorders of Pregnancy & Gestational Diabetes 13.3 Thyroid Disease & Venous Thromboembolism in Pregnancy 13.4 Menopause & Menopausal Hormone Therapy 13.5 Abnormal Uterine Bleeding, Endometrial Disease & Gynecologic Cancer Screening 13.6 Breast Disorders & Diseases of the Vulva and Vagina 13.7 Menstrual Disorders, Fibroids, Endometriosis & Early Pregnancy Complications

15 Chapter 14: Geriatric Syndromes (3% of Exam)

14.1 Comprehensive Geriatric Assessment & Frailty 14.2 Falls, Gait Assessment & Polypharmacy 14.3 Urinary Incontinence & Pressure Injuries in Older Adults 14.4 Mild Cognitive Impairment, Dementia & Its Subtypes 14.5 Delirium & the Pharmacotherapy of Cognitive Disorders 14.6 Palliative Care, Hospice & Advance Care Planning 14.7 Chronic Wounds, Nutrition, Swallowing, Constipation & Hip Fracture 14.8 Sensory Impairment, Dizziness, Elder Mistreatment & Care Settings

16 Chapter 15: Allergy & Immunology (2% of Exam)

15.1 Anaphylaxis: Recognition & Emergency Management 15.2 Urticaria & Angioedema 15.3 Drug Allergy, Desensitization & Adult Immunodeficiency 15.4 Food Allergy, Insect Venom Hypersensitivity, Serum Sickness & Contrast Reactions 15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders

17 Chapter 16: Preventive Medicine, Immunization & Clinical Epidemiology

16.1 The USPSTF Framework & Evidence-Based Cancer Screening 16.2 Cardiovascular & Metabolic Screening and Primary Prevention 16.3 Adult Immunization & Vaccines in Special Populations 16.4 Clinical Epidemiology, Biostatistics & Study Design

18 Chapter 17: Miscellaneous - Ethics, Patient Safety & Quality Improvement (2% of Exam)

17.1 Principles of Bioethics & Decisional Capacity 17.2 Informed Consent, Treatment Refusal & Special Scenarios 17.3 Surrogate Decision-Making, Advance Directives & Confidentiality 17.4 Patient Safety Science, Medical Error & Diagnostic Reasoning 17.5 Quality Improvement Methods, Health Disparities & Health Equity

19 Chapter 18: Perioperative Medicine & Medical Consultation

18.1 Preoperative Cardiovascular Risk Assessment 18.2 Preoperative Pulmonary Risk & Perioperative Medication Management 18.3 Perioperative Anticoagulation, Bridging & Postoperative Complications

20 Chapter 19: Ophthalmology (1% of Exam)

19.1 The Acute Red Eye & Ophthalmic Emergencies 19.2 Painless Vision Loss & Chronic Ophthalmic Disease 19.3 Uveitis, Scleritis & Orbital Disease

21 Chapter 20: Otolaryngology & Dental Medicine (1% of Exam)

20.1 Dizziness, Vertigo & Epistaxis 20.2 Ear Disorders, Hearing Loss & Upper Respiratory Infections 20.3 Oral Cavity, Salivary Gland, Laryngeal & Taste and Smell Disorders

12.2 Acne, Rosacea & Cutaneous Infections

Key Takeaways Explain This Topic AI

Acne vulgaris and rosacea are the two topics enumerated under acne and rosacea.

Dermatophytes, herpes zoster and varicella, viral exanthems, cellulitis, necrotizing infection, lymphadenitis and ectoparasites are enumerated under skin and soft tissue infections.

Isotretinoin requires pregnancy prevention with monitoring because of severe teratogenicity.

Eczema herpeticum is a dermatologic emergency in which herpes simplex disseminates across eczematous skin and requires prompt systemic acyclovir.

Topical corticosteroids applied to undiagnosed dermatophyte infection produce tinea incognito with an altered, less recognizable appearance.

Last updated: August 2026

Rosacea

Pathophysiology: A chronic centrofacial inflammatory disorder characterized by abnormal neurovascular reactivity, innate immune hyperreactivity (upregulation of toll-like receptor 2 [TLR2] and cathelicidin antimicrobial peptides [LL-37]), and proliferation of Demodex folliculorum mites within sebaceous follicles.

Clinical Subtypes & Differentiation:

Rosacea Subtype Primary Clinical Features Common Triggers First-Line Management

1. Erythematotelangiectatic (ETR) Persistent central facial erythema, flushing episodes, and fine branching telangiectasias across cheeks, nose, and chin Hot beverages, spicy foods, alcohol, temperature changes, emotional stress, UV light Avoid known triggers; broad-spectrum SPF >=30 sunscreen; topical alpha-adrenergic vasoconstrictors ( Brimonidine 0.33% gel or Oxymetazoline 1% cream ); Pulsed-dye laser (PDL) for fixed telangiectasias

2. Papulopustular Central facial erythema with dome-shaped inflammatory papules and pustules; NO comedones (distinguishes from acne vulgaris) Same dietary, thermal, and UV triggers Mild/Moderate: Topical Metronidazole 0.75-1% gel/cream , Topical Ivermectin 1% cream (anti-parasitic against Demodex + anti-inflammatory), or Topical Azelaic acid 15% gel .; Moderate/Severe: Add Oral Doxycycline (sub-antimicrobial dose 40 mg daily [30 mg IR / 10 mg DR] or 50-100 mg daily)

3. Phymatous Marked sebaceous gland hyperplasia and fibrous connective tissue hypertrophy leading to irregular, thickened, lobulated skin; most commonly affects nose ( rhinophyma ), predominantly in men Chronic progressive inflammation Early: Oral Isotretinoin; Advanced: Surgical debulking, electrosurgery, or ablative CO2 laser resurfacing

4. Ocular Rosacea Blepharitis, conjunctival hyperemia, chalazia/styes, gritty foreign-body sensation, dry eyes, photophobia; can lead to corneal vascularization/ulceration Meibomian gland dysfunction Eyelid hygiene, warm compresses, artificial tears, oral Doxycycline, topical ophthalmic Cyclosporine

Acne Vulgaris

Pathophysiology: A multifactorial disorder of the pilosebaceous unit involving 4 primary pathogenic events: (1) Follicular hyperkeratinization obstructing the pilosebaceous follicle (forming microcomedones); (2) Androgen-stimulated excess sebum production; (3) Proliferation of Cutibacterium acnes (formerly Propionibacterium acnes ) within sebum-rich microenvironments; (4) Follicular rupture and innate immune inflammation mediated by neutrophils and lymphocytes.

Morphology: Non-inflammatory comedones (open [blackheads] vs closed [whiteheads]) and inflammatory lesions (erythematous papules, pustules, deep tender nodules, and pseudocysts). May heal with post-inflammatory hyperpigmentation or atrophic/hypertrophic scarring.

Stepwise Treatment Algorithm:

Mild Comedonal Acne: Topical Retinoid monotherapy ( Adapalene 0.1-0.3% , Tretinoin 0.025-0.1% , or Tazarotene 0.05-0.1% ) applied once nightly. Normalizes follicular desquamation, prevents new microcomedones, and promotes lesion clearance.

Mild-to-Moderate Inflammatory Acne: Combination of Topical Retinoid + Benzoyl Peroxide (BPO 2.5-5%) +/- Topical Antibiotic (Clindamycin 1%) .

Crucial Rule: Never prescribe topical antibiotic monotherapy (e.g., clindamycin alone) due to rapid development of bacterial resistance; always combine with Benzoyl Peroxide, which generates bactericidal reactive oxygen species with zero bacterial resistance.

Moderate-to-Severe Inflammatory Acne: Topical Retinoid + BPO + Oral Antibiotic ( Doxycycline 50-100 mg PO BID or Minocycline 50-100 mg PO BID ). Limit oral antibiotic duration to <=3 to 4 months to prevent systemic resistance. In post-pubertal females, consider antiandrogenic hormonal therapies: Combined Oral Contraceptives (COCs) containing drospirenone or norgestimate, or Spironolactone (50-100 mg daily) .

Severe Nodulocystic, Scarring, or Treatment-Refractory Acne: Oral Isotretinoin (13-cis-retinoic acid) (cumulative target dose 120-150 mg/kg over 4-6 months). Isotretinoin is the only curative monotherapy that addresses all 4 pathogenic mechanisms.

Safety, Monitoring & Regulations: Extreme teratogenicity (hydrocephalus, microtia, conotruncal cardiac defects); mandates enrollment in the iPLEDGE Risk Evaluation and Mitigation Strategy (REMS) program requiring two negative pregnancy tests prior to initiation, two forms of contraception, and monthly negative pregnancy tests before each 30-day prescription. Baseline and periodic monitoring: Liver Function Tests (LFTs) , fasting lipid panel (triglycerides/cholesterol) , and screening for depressive symptoms/mood changes. Common side effects: severe cheilitis, xerosis, epistaxis, myalgias, and elevated liver enzymes/triglycerides.

• 1. Infectious Dermatoses & Mimickers
• Cellulitis vs. Erysipelas vs. Stasis Dermatitis

Differentiating acute bacterial dermohypodermal infections from chronic vascular pseudocellulitis is among the most heavily tested dermatology topics in hospital and outpatient internal medicine.

Clinical Parameter Cellulitis Erysipelas Stasis Dermatitis (Pseudocellulitis)

Anatomical Depth Deep dermis and subcutaneous fat Superficial dermis and upper dermal lymphatics Epidermis and superficial dermis secondary to chronic venous hypertension

Typical Etiology Beta-hemolytic Streptococci ( S. pyogenes , Group G/C/B) > Staphylococcus aureus Group A Beta-hemolytic Streptococcus ( Streptococcus pyogenes ) Chronic venous insufficiency, valvular incompetence, capillary leakage, hemosiderin deposition

Laterality Unilateral (>98% of cases) Unilateral Bilateral (symmetric lower extremities)

Margin & Appearance Poorly demarcated , spreading flat erythematous border; warm, tender, edematous Sharply demarcated, raised, indurated border ; fiery red, orange-peel ( peau d'orange ) texture; prominent facial (malar) or lower leg involvement Poorly demarcated, brown-red hemosiderin hyperpigmentation , eczematous scaling, xerosis, varicose veins, pitting edema, lipodermatosclerosis ("inverted champagne bottle" leg)

Onset & Systemic Signs Subacute (days), moderate fever/leukocytosis Acute, explosive onset (hours) with high fever, chills, rigors, systemic toxicity Chronic, indolent (months to years), afebrile, normal WBC count

First-Line Treatment Oral Cephalexin 500 mg QID or IV Cefazolin 1-2 g q8h (non-purulent).; Add MRSA coverage ( TMP-SMX, Doxycycline, or IV Vancomycin ) if purulent drainage, abscess, injection drug use, or severe toxicity Oral Penicillin VK 500 mg QID , Amoxicillin 500 mg TID , or IV Cefazolin / Penicillin G Leg elevation , graduated compression stockings (20-30 mmHg), thick emollients, mid-potency topical steroids (Triamcinolone 0.1%) for acute eczematous flare. NO SYSTEMIC ANTIBIOTICS