44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes

ABFM Family Medicine Certification Study Guide Exam

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

1.1 Exam Blueprint, FMCLA vs. One-Day Exam & Board Scoring 1.2 Clinical Reasoning, Test-Taking Strategy & Ambiguity Management 1.3 Evidence-Based Medicine & Clinical Practice Guidelines in Primary Care

2 Chapter 2: Healthcare Systems, Practice Management & Quality

2.1 Practice Management, Billing, Coding & Documentation 2.2 Quality Improvement, Patient Safety & Diagnostic Stewardship 2.3 Interprofessional Team-Based Care & Care Coordination

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

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4 Chapter 4: Lifestyle Counseling & Behavior Change

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5 Chapter 5: Nutrition, Physical Activity & Chronic Disease Prevention

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6 Chapter 6: Routine Adult Immunizations

6.1 ACIP Adult Respiratory Vaccines: Influenza, COVID-19, RSV & Pneumococcal 6.2 ACIP Adult Non-Respiratory Vaccines: Tdap, Shingrix, HPV & Hep B 6.3 Immunizations in Special Populations: Pregnancy, Asplenia & Immunocompromise

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

9.1 Cardiovascular Disease & Hypertension Screening 9.2 Type 2 Diabetes Screening & Prediabetes Risk Stratification 9.3 Abdominal Aortic Aneurysm & Osteoporosis Screening

10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

10.1 Breast Cancer Screening & Risk-Assessment 10.2 Cervical Cancer Screening & ASCCP Algorithms 10.3 Skin Cancer Clinical Assessment & Counseling

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

12.1 Sexual Health Counseling & Risk-Reduction Strategies 12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis 12.3 Bloodborne Infectious Disease Screening: HIV & Hepatitis C

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

14.1 Acute Coronary Syndromes & Myocardial Infarction 14.2 Acute Chest Pain Risk Stratification & Triage 14.3 Acute or Critical Valvular Heart Emergencies

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

15.1 Acute Atrial & Ventricular Arrhythmias 15.2 Acute Decompensated Heart Failure & Cardiogenic Shock 15.3 Hypertensive Emergency & Urgency Management

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

44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes

Key Takeaways Explain This Topic AI

Inflammatory myopathies cause painless or mildly painful symmetrical proximal muscle weakness: Polymyositis features CD8+ T-cell endomysial infiltrates and anti-Jo-1 antibodies, whereas Dermatomyositis features CD4+ perimysial microangiopathy plus pathognomonic cutaneous findings (Heliotrope rash, Gottron papules, shawl and V signs) and mandates age-appropriate cancer screening for occult malignancy.

Polymyalgia Rheumatica (PMR) presents in patients aged >=50 with severe bilateral shoulder, hip girdle, and neck aching and morning stiffness >45 minutes, markedly elevated ESR (>40-50 mm/hr) and CRP, but strictly NORMAL serum creatine kinase (CK) and intact intrinsic muscle strength; it responds dramatically to low-dose prednisone (15-20 mg/day within 48-72 hours) and requires vigilant screening for Giant Cell Arteritis.

Rhabdomyolysis is diagnosed by serum CK >5 times the upper limit of normal (often >10,000-100,000 U/L); classic presentation includes the triad of severe myalgias, weakness, and dark tea-colored urine with a dipstick positive for 'blood' but an absence of microscopic red blood cells.

Immediate, aggressive intravenous isotonic crystalloid hydration (400-1,000 mL/hr targeting a urine output of 200-300 mL/hr) is the cornerstone of rhabdomyolysis therapy to prevent acute tubular necrosis, myoglobin cast nephropathy, and fatal hyperkalemia.

Post-viral pain syndromes following influenza, COVID-19, chikungunya, or EBV manifest with persistent diffuse myalgias, arthralgias, and fatigue; management focuses on symptom control with non-opioid analgesics, reassurance, and graded physical rehabilitation.

Last updated: September 2026

Diagnostic Framework for Generalized Muscle Pain & Weakness

The clinical evaluation of a patient presenting with generalized muscle pain (myalgias) or weakness requires a systematic distinction between true objective muscle weakness (inability of a muscle to exert normal contractile power against resistance) and asthenia or antalgic limitation (fatigue, lethargy, or reluctance to move due to joint or tendon pain).

Neurologic vs. Myopathic Localization

Myopathic Weakness : Characteristically manifests as symmetrical proximal muscle weakness (shoulder abductors, hip flexors, neck flexors) with preservation of distal dexterity until late stages. Patients report difficulty rising from a low chair without pushing with arms, climbing stairs, or lifting objects overhead (e.g., placing dishes on high shelves). Deep tendon reflexes and sensation remain intact.

Neuropathic Weakness : Typically asymmetric, involves distal muscle groups (foot drop, weak wrist extension), and is accompanied by objective sensory loss (numbness, paresthesias) and depressed or absent deep tendon reflexes.

Neuromuscular Junction Disorders (e.g., Myasthenia Gravis) : Characterized by fluctuating, fatigable weakness exacerbated by repetitive exertion and relieved by rest, with prominent cranial nerve involvement (ptosis, diplopia, dysarthria, dysphagia) and normal muscle enzymes (CK).

Idiopathic Inflammatory Myopathies: Polymyositis vs. Dermatomyositis

Polymyositis (PM) and Dermatomyositis (DM) are systemic autoimmune connective tissue diseases characterized by chronic immune-mediated striated muscle inflammation resulting in progressive proximal muscle weakness and elevated serum muscle enzymes. COMPARISON OF POLYMYOSITIS & DERMATOMYOSITIS

• Feature Polymyositis (PM) Dermatomyositis (DM)
• ═════════════════════════════════════════════════════════════════════════════════════════
• Immunopathogenesis Cell-mediated: CD8+ cytotoxic Humoral/vascular: CD4+ T cells,
• T cells invade non-necrotic B cells, complement (C5b-9) MAC
• endomysial muscle fibers damages perimysial capillaries

• Muscle Biopsy Endomysial mononuclear Perimysial and perivascular
• infiltrates; muscle necrosis infiltrates; perifascicular atrophy

Cutaneous Signs ABSENT PATHOGNOMONIC:

• Heliotrope rash, Gottron papules,
• shawl sign, V-sign, holster sign

• Malignancy Risk Modest increase (~1.5-2x) VERY HIGH (20% to 30% of adults);
• Mandatory comprehensive screening

• Autoantibodies Anti-Jo-1 (antisynthetase); Anti-Mi-2, anti-TIF1-gamma,
• Anti-SRP, ANA anti-NXP-2, anti-MDA5

• First-Line Therapy High-dose oral corticosteroids High-dose oral corticosteroids
• (prednisone 1 mg/kg/day) + (prednisone 1 mg/kg/day) +
• steroid-sparing immunosuppressant steroid-sparing immunosuppressant
• ═════════════════════════════════════════════════════════════════════════════════════════
• 1. Polymyositis (PM)

Pathophysiology : MHC Class I antigens (HLA-ABC) are aberrantly expressed on striated sarcolemma. Autoreactive CD8+ cytotoxic T lymphocytes and macrophages invade non-necrotic endomysial muscle fibers, releasing perforin and granzyme to cause myofiber necrosis.

Clinical Presentation : Insidious, progressive, painless or mildly aching symmetrical proximal weakness developing over weeks to months. Pharyngeal and upper esophageal striated muscle involvement occurs in up to 30% of patients, presenting with dysphagia, nasal regurgitation, and high aspiration pneumonia risk.

Laboratory Findings : Serum Creatine Kinase (CK) is markedly elevated (5 to 50 times the upper limit of normal; typically 1,000 to >10,000 U/L). Elevated aldolase, lactate dehydrogenase (LDH), and serum transaminases (AST/ALT; frequently misinterpreted as liver disease until CK is checked).

Antisynthetase Syndrome : A recognized clinical subgroup associated with anti-Jo-1 (anti-histidyl-tRNA synthetase) antibodies, characterized by the clinical triad of inflammatory myopathy, interstitial lung disease (ILD) , non-erosive polyarthritis, Raynaud phenomenon, and "mechanics' hands" (hyperkeratotic, cracked, scaling fissures along the palmar and lateral surfaces of the fingers).

2. Dermatomyositis (DM) & Pathognomonic Cutaneous Signs

Pathophysiology : Complement-mediated microangiopathy. Deposition of the C5b-9 membrane attack complex (MAC) within endomysial capillary endothelial cells leads to capillary thrombosis, microvascular ischemia, and characteristic perifascicular myofiber atrophy .

Pathognomonic Cutaneous Signs :

Heliotrope Rash : Violaceous (purplish-pink) erythema involving the upper eyelids, often accompanied by periorbital edema.

Gottron Papules : Pathognomonic violaceous or erythematous, flat-topped, lichenoid papules and plaques overlying the dorsal surfaces of the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints.

Gottron Sign : Symmetrical macular erythema with or without scaling over the extensor surfaces of the elbows, patellae, and medial malleoli.

Shawl Sign : Widespread violaceous macular erythema distributed across the posterior neck, upper back, and shoulders.

V-Sign : Confluent erythematous eruption over the anterior lower neck and upper chest (photo-distributed).

Holster Sign : Violaceous macules on the lateral hips and thighs (trochanteric regions).

Periungual Telangiectasias : Capillary dilation, tortuosity, and cuticular overgrowth along the proximal nailfold.

The Mandatory Malignancy Workup in Dermatomyositis

Important

CANCER SCREENING MANDATE IN DERMATOMYOSITIS Up to 20% to 30% of adult patients with dermatomyositis have an underlying occult malignancy (paraneoplastic phenomenon). The highest relative risk is for ovarian cancer in females, followed by breast, lung, gastrointestinal (colorectal, gastric, pancreatic) cancers, and non-Hodgkin lymphoma (as well as nasopharyngeal carcinoma in patients of Southeast Asian ancestry).

Every adult newly diagnosed with dermatomyositis must undergo comprehensive, age- and sex-appropriate malignancy screening: complete pelvic examination with transvaginal pelvic ultrasound and serum CA-125 in women, mammography, PSA in men, colonoscopy, computed tomography (CT) of the chest, abdomen, and pelvis, and fecal occult blood testing. Screening should be repeated annually for at least 3 years following diagnosis.

Polymyalgia Rheumatica (PMR) & Giant Cell Arteritis (GCA)

Polymyalgia Rheumatica is a common chronic inflammatory condition of older adults characterized by aching and morning stiffness in the shoulder girdles, hip girdles, and neck.

Clinical Presentation & Diagnostic Criteria

Demographics : Almost exclusively affects individuals aged >=50 years (peak incidence between 70 and 80 years); females outnumber males 2:1.

Clinical Presentation : Acute or subacute onset (days to weeks) of bilateral, symmetrical aching and stiffness in the proximal girdles : shoulders, pelvic girdle (hips/buttocks/thighs), and cervical spine.

Profound Morning Stiffness : Cardinal symptom lasting >45 to 60 minutes (often lasting multiple hours); patients report severe difficulty getting out of bed, rising from a toilet, or lifting their arms to put on a jacket or brush their hair.

Physical Examination Hallmark :

Active range of motion of the shoulders and hips is severely restricted due to pain.

TRUE MUSCLE STRENGTH IS NORMAL (5/5) once pain is accounted for! There is NO intrinsic muscle weakness, and passive range of motion is relatively preserved.

Musculoskeletal ultrasound characteristically reveals bilateral subacromial/subdeltoid bursitis , biceps tenosynovitis, and trochanteric bursitis.

Laboratory Findings :

Markedly elevated ESR (>40-50 mm/hr, often >100 mm/hr) and elevated C-reactive protein (CRP).

Serum Creatine Kinase (CK) and aldolase are completely NORMAL (essential differentiating factor from polymyositis).

Mild normocytic normochromic anemia of chronic disease; negative rheumatoid factor and anti-CCP.

Dramatic Response to Low-Dose Corticosteroids

First-Line Regimen : Oral Prednisone 15 to 20 mg daily .

Diagnostic and Therapeutic Hallmark : Patients exhibit a dramatic, rapid clinical response within 48 to 72 hours (often describing near-total resolution of pain and stiffness). If a patient fails to show substantial improvement within 7 days, the diagnosis of PMR must be fundamentally questioned.

Tapering Schedule : Continue initial dose for 2 to 4 weeks until symptoms remit and ESR/CRP normalize, then taper gradually over 12 to 24 months to avoid inflammatory relapse.

Mandatory Screening for Giant Cell Arteritis (GCA / Temporal Arteritis)

Caution

THE PMR-GCA LINK: PREVENTING IRREVERSIBLE BLINDNESS Approximately 15% to 20% of patients with PMR have concomitant Giant Cell Arteritis , and 40% to 50% of patients with GCA have PMR.

Clinicians must screen for GCA symptoms at EVERY clinical encounter:

• New-onset unilateral temporal or frontal headache
• Scalp tenderness (pain while brushing hair or resting head on a pillow)

• Jaw claudication (fatigue and pain in the masseter muscles while chewing food; highest positive likelihood ratio for GCA)
• Visual disturbances: amaurosis fugax (transient painless monocular vision loss), diplopia, or visual field defects

• Thickened, tender, nodular, or pulseless temporal artery

IF GCA IS SUSPECTED : Immediately initiate HIGH-DOSE oral Prednisone (40 to 60 mg daily) or IV methylprednisolone (1,000 mg daily if visual symptoms are present) and arrange an urgent temporal artery biopsy. NEVER DELAY CORTICOSTEROID THERAPY PENDING BIOPSY ; immediate high-dose steroids prevent catastrophic, permanent blindness from anterior ischemic optic neuropathy (AION).

Rhabdomyolysis: Pathophysiology & Etiologies

Rhabdomyolysis is an acute, life-threatening syndrome caused by skeletal muscle necrosis and the catastrophic release of intracellular myocellular contents (myoglobin, creatine kinase, electrolytes, purines) into the systemic circulation.

Pathophysiologic Cascade

Direct mechanical trauma, sustained muscle ischemia, or severe metabolic ATP depletion impairs the sarcolemmal Na+/K+-ATPase and Ca2+-ATPase pumps . Intracellular sodium accumulates, reversing the Na+/Ca2+ exchanger and driving a massive, uncontrolled influx of ionized calcium into the myoplasm . Intracellular hypercalcemia activates calcium-dependent neutral proteases (calpains) and phospholipase A2, initiating myofibrillar autolysis, mitochondrial destruction, and sarcolemmal rupture. Massive quantities of myoglobin, creatine kinase, potassium, phosphorus, and nucleic acids flood the extracellular space. COMMON ETIOLOGIES OF RHABDOMYOLYSIS

• Etiologic Category Specific Causes & Clinical Contexts
• ═════════════════════════════════════════════════════════════════════════════════════════
• Trauma & Compression • Prolonged immobilization ("down time" after fall, stroke, coma,
• or overdose of opioids, sedatives, or ethanol)
• Crush injuries, vehicular entrapment, compartment syndrome
• High-voltage electrical injuries, severe third-degree burns

• Exertional Overload • Extreme strenuous exertion in unconditioned individuals (CrossFit,
• marathon running, military boot camp)
• Exertional heat stroke, strenuous exertion with sickle cell trait
• Severe prolonged seizures, status epilepticus, delirium tremens

• Drugs & Toxins • Statins (HMG-CoA reductase inhibitors), especially combined with
• gemfibrozil or CYP3A4 inhibitors (clarithromycin, azoles)
• Illicit psychostimulants: Cocaine, methamphetamine, MDMA (ecstasy)
• Alcohol abuse (toxic myopathy, immobilization, hypokalemia)
• Neuroleptic Malignant Syndrome (NMS), Malignant Hyperthermia

• Metabolic & Endocrine • Severe hypokalemia (<2.5 mEq/L) causing impaired muscle blood flow
• Severe hypophosphatemia (<1.0 mg/dL) depleting muscle ATP
• Diabetic ketoacidosis (DKA), Hyperosmolar Hyperglycemic State (HHS)
• Severe profound hypothyroidism (myxedema coma)

• Systemic Infections • Viral: Influenza A and B, SARS-CoV-2 (COVID-19), enteroviruses, EBV
• Bacterial: Legionella pneumophila, Streptococcus pneumoniae, sepsis
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• Clinical Presentation, Complications & Urinalysis Hallmarks
• The Classic Triad

The classic clinical triad consists of:

Severe Myalgias : Muscle pain and profound tenderness, most prominent in proximal muscle groups (thighs, calves, lower back).

Generalized Proximal Muscle Weakness : Difficulty standing, walking, or lifting arms.

Dark Reddish-Brown Urine : Described as "tea-colored", "cola-colored", or smoky urine. Note : The full triad is present in fewer than 10% of patients at initial presentation! Swelling, edema, and firmness of affected muscle compartments may be the only physical signs.

Diagnostic Hallmarks: Serum CK & The Urinalysis Discrepancy

Serum Creatine Kinase (CK) : The single most sensitive and definitive diagnostic test. A diagnosis of rhabdomyolysis is established when serum CK exceeds 5 times the upper limit of normal (typically >1,000 U/L) . In clinically significant rhabdomyolysis, levels routinely exceed 10,000 to >100,000 U/L (and can reach 500,000+ U/L). Serum CK rises within 2 to 12 hours of muscle injury, peaks at 24 to 72 hours, and declines by 40% to 50% daily once muscle necrosis ceases.

The Pathognomonic Urinalysis Discrepancy :

Urine Dipstick: STRONGLY POSITIVE (3+ to 4+) FOR "BLOOD" (HEME) .

Microscopic Examination: ABSENCE OF RED BLOOD CELLS (0 to 2 RBCs/HPF) .

Mechanism : The urine dipstick uses an orthotolidine reagent that reacts with the heme moiety present in both hemoglobin and myoglobin . In rhabdomyolysis, massive circulating free myoglobin is filtered by the glomeruli into the tubular lumen (myoglobinuria). Because the dipstick cannot differentiate myoglobin from intact erythrocytes, it triggers a strong positive reaction, but microscopic examination reveals no intact red blood cells.

Life-Threatening Acute Complications

Acute Kidney Injury (AKI) : Occurs in 15% to 50% of patients. Three synergistic mechanisms drive renal injury:

Renal Vasoconstriction : Intravascular volume depletion and cytokine release trigger intense renal arteriolar vasoconstriction.

Intratubular Cast Formation : In the acidic environment of the distal convoluted tubule (urine pH <5.6), filtered myoglobin precipitates with Tamm-Horsfall mucoprotein , forming obstructive pigmented casts that block tubular lumen flow.

Direct Cytotoxicity & Lipid Peroxidation : Ferrihemate released from degraded myoglobin catalyzes the generation of reactive oxygen species (Fenton reaction), causing peroxidation of proximal tubular cell membranes and direct acute tubular necrosis (ATN).

Hyperkalemia : Catastrophic, rapid release of intracellular potassium into the extracellular compartment can produce fatal cardiac arrhythmias (peaked T waves, PR prolongation, wide QRS, ventricular fibrillation, asystole).

Hyperphosphatemia & Early Hypocalcemia : Intracellular phosphate binds circulating ionized calcium, causing metastatic calcium phosphate deposition into damaged necrotic muscle beds. Warning : Later in the recovery phase, this deposited calcium is remobilized back into circulation, leading to late hypercalcemia.

Hyperuricemia : Massive hepatic conversion of intracellular purines released from degenerated muscle cell nuclei.

Compartment Syndrome : Intracellular swelling within unyielding fascial envelopes compromises microvascular perfusion; requires immediate monitoring of compartment pressures and emergent fasciotomy if pressure exceeds 30 mmHg or delta pressure (diastolic BP minus compartment pressure) is <30 mmHg.

Disseminated Intravascular Coagulation (DIC) : Triggered by the release of intracellular thromboplastin and procoagulants into systemic circulation.

• Evidence-Based Treatment Protocol for Rhabdomyolysis
• 1. Immediate, Aggressive Intravenous Crystalloid Resuscitation

Aggressive volume expansion is the cornerstone of therapy to prevent myoglobin cast precipitation and acute tubular necrosis:

Fluid Selection : Isotonic crystalloids— Normal Saline (0.9% NaCl) or Lactated Ringer's .

Initial Rate : Administer 400 to 1,000 mL/hr intravenously immediately upon clinical suspicion.

Urine Output Target : Titrate intravenous fluids to achieve and maintain an aggressive target urine output of 200 to 300 mL/hr (3 to 5 mL/kg/hr) until myoglobinuria has cleared and serum CK levels trend below 5,000 U/L.

2. Cardiac Telemetry & Aggressive Electrolyte Management

Obtain an immediate 12-lead ECG and initiate continuous telemetry monitoring for signs of hyperkalemic cardiotoxicity.

Management of Hyperkalemia :

Membrane stabilization: Intravenous Calcium Gluconate (10 mL of 10% solution over 2-3 minutes) if ECG changes (peaked T waves, QRS widening) are observed.

Intracellular potassium shifting: Regular insulin 10 units IV with 50 mL 50% Dextrose (D50W), nebulized albuterol (10-20 mg).

Potassium elimination: Oral sodium zirconium cyclosilicate (Lokelma) or emergent hemodialysis if refractory.

Caution

DO NOT ROUTINELY ADMINISTER CALCIUM FOR ASYMPTOMATIC HYPOCALCEMIA Intravenous calcium should NOT be administered to treat early hypocalcemia in rhabdomyolysis unless the patient exhibits life-threatening hyperkalemic cardiotoxicity or severe symptomatic tetany/seizures. Administering supplemental calcium drives further calcium precipitation into damaged muscle tissue, worsening rhabdomyolysis and exacerbating severe, dangerous rebound hypercalcemia during the recovery phase.

3. Role of Urine Alkalinization (Sodium Bicarbonate) & Diuretics

Routine intravenous sodium bicarbonate infusion or mannitol administration is NOT supported by clinical trials over aggressive saline hydration alone .

Bicarbonate infusion (100-150 mEq sodium bicarbonate in D5W) can be selectively considered ONLY if severe systemic metabolic acidosis exists (arterial pH <7.1) or if urine pH remains <6.5 despite adequate hydration, but it carries a significant risk of worsening hypocalcemia and alkalemia. Aggressive isotonic hydration remains the primary therapeutic mandate.

Post-Viral Myalgias & Chronic Post-Viral Pain Syndromes

Viral infections are among the most frequent precipitants of acute generalized myalgias in ambulatory family medicine. While most episodes resolve spontaneously within 7 to 14 days, certain pathogens can trigger protracted, debilitating musculoskeletal pain syndromes.

Causative Pathogens & Clinical Characteristics

Influenza A and B : Causes acute, intense, diffuse myalgias affecting the back, thighs, and calves, accompanied by fever, chills, and respiratory symptoms. Serum CK may show mild, transient elevations (<2-3 times normal), but frank rhabdomyolysis is rare.

SARS-CoV-2 (COVID-19 & Post-COVID Conditions / PASC) : Acute COVID-19 frequently presents with prominent myalgias. Up to 15% to 25% of patients develop Post-Acute Sequelae of SARS-CoV-2 ("Long COVID"), characterized by persistent diffuse musculoskeletal pain, exercise intolerance, post-exertional malaise (PEM), profound cognitive fatigue ("brain fog"), and autonomic dysfunction (postural orthostatic tachycardia syndrome - POTS).

Chikungunya Virus : An Aedes mosquito-borne alphavirus endemic to the Caribbean, South America, and tropical regions. Characterized by acute high fever and excruciating, debilitating symmetric polyarthralgia and myalgias predominantly affecting small distal joints (wrists, ankles, hands). Up to 40% to 50% of infected individuals develop chronic chikungunya arthralgia/myalgia lasting months to years post-infection.

Epstein-Barr Virus (EBV) : Acute infectious mononucleosis frequently triggers protracted post-viral fatigue and generalized muscle aching persisting for months.

Diagnostic Approach & Supportive Management

Workup : Rule out inflammatory myopathies (serum CK and aldolase are normal or only minimally elevated), systemic vasculitis/PMR (ESR and CRP are typically normal or only mildly elevated), and primary thyroid disease (normal TSH).

Management Principles :

Reassurance regarding the absence of progressive destructive joint or muscle disease.

Multimodal non-opioid analgesia: scheduled acetaminophen and short courses of oral NSAIDs for acute inflammatory flares.

Non-pharmacologic rehabilitation: structured, low-intensity graded exercise therapy (avoiding severe exertion that precipitates post-exertional malaise), pacing strategies, and cognitive behavioral therapy.

Loading diagram... Diagnostic & Management Algorithm for Acute Myalgias, Weakness & Rhabdomyolysis