Study guide
6.8 The Vasculitides
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
6.8 The Vasculitides
Key Takeaways Explain This Topic AI
Polyarteritis nodosa, eosinophilic granulomatosis with polyangiitis, leukocytoclastic vasculitis, large-vessel vasculitis and ANCA-associated vasculitis are the enumerated topics.
Corticosteroids must be started immediately in suspected giant cell arteritis without waiting for temporal artery biopsy, which remains informative for up to two weeks.
Proteinase-3 ANCA associates with granulomatosis with polyangiitis and myeloperoxidase ANCA with microscopic polyangiitis.
Polyarteritis nodosa spares the lungs and glomeruli, is associated with hepatitis B, and is diagnosed by angiography or tissue biopsy rather than by ANCA.
Mixed cryoglobulinemia is strongly associated with hepatitis C, and definitive therapy is antiviral treatment of the underlying infection.
Last updated: August 2026
- 1. Large-Vessel & Medium-Vessel Vasculitides
- 1. Giant Cell Arteritis (GCA / Temporal Arteritis)
Epidemiology: Most common systemic vasculitis in adults; occurs exclusively in patients age >= 50 years (peak incidence 70–80 years), female predominance (2–3:1), Northern European ancestry.
Clinical Presentation: New onset unilateral temporal headache, scalp tenderness (pain with brushing hair), jaw claudication (fatigue/pain in masseter muscles while chewing; highest positive likelihood ratio ~4.0 for GCA) , tongue claudication, constitutional symptoms (fever, weight loss), and prominent tender, nodular, pulseless temporal arteries.
Polymyalgia Rheumatica (PMR) Overlap: Up to 50% of GCA patients have concurrent PMR (symmetric aching and morning stiffness >45 min in shoulders, neck, and pelvic girdle without true muscle weakness; dramatic response to low-dose prednisone 15–20 mg/day).
Catastrophic Complication: Ischemic Optic Neuropathy (Anterior Ischemic Optic Neuropathy [AION]) secondary to posterior ciliary artery occlusion. Presents as painless transient monocular vision loss ( amaurosis fugax ) rapidly progressing to permanent, irreversible blindness in the affected eye, with high risk of contralateral eye involvement within days if untreated.
Diagnostic Workup:
Markedly elevated ESR (typically >50 to >100 mm/h) and elevated CRP; normocytic anemia and thrombocytosis.
Temporal Artery Biopsy (Gold Standard): Transmural granulomatous inflammation with mononuclear cell infiltration, internal elastic lamina disruption, and multinucleated giant cells. Biopsy segment should be >=2–3 cm to avoid false negatives due to skip lesions .
Color Doppler Ultrasound: Demonstrates a hypoechoic circumferential mural edema around the temporal artery lumen ( "halo sign" ).
EMERGENCY Management Protocol:
MANDATORY Rule: Initiate immediate high-dose corticosteroids IMMEDIATELY upon clinical suspicion, BEFORE obtaining a temporal artery biopsy! Never delay steroid therapy for diagnostic testing.
Visual Symptoms Present: IV Methylprednisolone 1,000 mg daily for 3 consecutive days , followed by oral Prednisone 1 mg/kg/day (60 mg daily).
Uncomplicated GCA (No Visual Symptoms): Oral Prednisone 60 mg daily.
Biopsy remains histopathologically diagnostic up to 2 to 4 weeks after initiating steroids.
Steroid-Sparing Biologic: Tocilizumab (IL-6 receptor antagonist) is FDA-approved to maintain remission and reduce cumulative corticosteroid toxicity (GiACTA trial).
2. Takayasu Arteritis ("Pulseless Disease")
Epidemiology: Granulomatous panarteritis targeting the aorta and its primary major branches. Predominantly affects young females (<40 years old) , most frequently of Asian ancestry.
Clinical Presentation: Early constitutional phase (fever, malaise, weight loss, night sweats) followed by vascular occlusive phase: upper extremity claudication , asymmetric peripheral pulses , blood pressure difference >10 mmHg between upper extremities , subclavian/carotid arterial bruits, lightheadedness, renovascular hypertension (renal artery stenosis), and aortic root dilation with aortic regurgitation.
Diagnostics: Non-invasive CT Angiography (CTA) or Magnetic Resonance Angiography (MRA) demonstrating diffuse concentric vessel wall thickening, luminal narrowing, occlusion, and post-stenotic aneurysmal dilation of the aortic arch, subclavian, carotid, and renal arteries.
Management: High-dose oral corticosteroids (Prednisone 1 mg/kg/day) + steroid-sparing immunosuppressive agents (Methotrexate, Azathioprine, Tocilizumab, or Anti-TNF biologics). Surgical revascularization or endovascular stenting is reserved for fixed, flow-limiting stenoses once active vascular inflammation is quiescent.
3. Polyarteritis Nodosa (PAN)
Pathophysiology: Systemic necrotizing vasculitis targeting medium-sized muscular arteries , causing transmural fibrinoid necrosis, internal elastic lamina destruction, microaneurysm formation, vascular thrombosis, and downstream organ infarction. Characteristically SPARES the pulmonary circulation (no pulmonary involvement) and does not involve small arterioles/glomeruli (no glomerulonephritis) .
Etiology: Idiopathic, or secondary to Hepatitis B Virus (HBV) infection (~30% of secondary cases, driven by HBsAg-anti-HBs immune complex deposition), and rarely Hepatitis C or Hairy Cell Leukemia.
Clinical Presentation:
Systemic: Fever, weight loss, malaise.
Renal: Renovascular hypertension (renal artery vasculitis leading to severe ischemia/renin release), flank pain from renal wedge infarctions. Note: Urinalysis shows minimal proteinuria without red cell casts (no GN) .
Neurologic: Mononeuritis multiplex (asymmetric motor/sensory peripheral neuropathy, e.g., wrist drop [radial nerve] or foot drop [peroneal nerve]) in 50–70% of patients.
Gastrointestinal: Severe postprandial abdominal pain ("intestinal angina"), mesenteric ischemia, bowel perforation, cholecystitis.
Cutaneous: Livedo reticularis , painful subcutaneous nodules along arterial tracks, digital ischemia/gangrene, and lower extremity ulcerations.
Genitourinary: Testicular pain or tenderness (orchitis).
Diagnostics: Negative ANCA (PAN is seronegative). Biopsy of symptomatic site (sural nerve, skin nodule, muscle) showing transmural necrotizing arteritis with fibrinoid necrosis. Mesenteric or Renal Angiography demonstrating multiple small aneurysms (microaneurysms 1–5 mm) and irregular segmental stenoses ( "string of beads" appearance ).
Treatment:
Idiopathic PAN: Glucocorticoids (Prednisone 1 mg/kg/day); add Cyclophosphamide for severe, organ-threatening, or life-threatening disease (Five-Factor Score >=1).
HBV-Associated PAN: Short-term corticosteroids + plasma exchange + antiviral therapy with Entecavir or Tenofovir (avoids prolonged immunosuppression that exacerbates viral replication).
- 2. Small-Vessel Vasculitides
- 1. ANCA-Associated Vasculitides (AAV)
AAVs are characterized by necrotizing small-vessel vasculitis with few or no immune deposits ( pauci-immune ), strongly associated with Antineutrophil Cytoplasmic Antibodies (ANCA) targeting proteinase-3 (PR3) or myeloperoxidase (MPO).
Feature Granulomatosis with Polyangiitis (GPA / Wegener) Microscopic Polyangiitis (MPA) Eosinophilic Granulomatosis with Polyangiitis (EGPA / Churg-Strauss)
Serology c-ANCA / PR3-ANCA positive (85–90%) p-ANCA / MPO-ANCA positive (70–80%) p-ANCA / MPO-ANCA positive (40–50%) (predominantly in patients with glomerulonephritis/neuropathy)
Pathology Necrotizing granulomatous inflammation of upper/lower respiratory tract + pauci-immune necrotizing crescentic glomerulonephritis. Non-granulomatous necrotizing vasculitis of small vessels + pauci-immune necrotizing crescentic glomerulonephritis. Eosinophil-rich necrotizing granulomatous inflammation involving respiratory tract + necrotizing vasculitis.
Upper Airway Severe destructive disease : chronic purulent/bloody rhinosinusitis, nasal crusting, saddle-nose deformity (nasal septal perforation), subglottic stenosis, mastoiditis, serous otitis media. Lacks destructive upper airway disease. Severe allergic rhinitis, nasal polyposis , chronic pansinusitis.
Lower Airway Multiple cavitary pulmonary nodules , thick-walled cavitary lesions, alveolar hemorrhage, cough, hemoptysis. Diffuse alveolar hemorrhage without lung cavities; interstitial fibrosis. Severe, adult-onset refractory asthma , transient migratory pulmonary infiltrates.
Renal Rapidly Progressive Glomerulonephritis (RPGN) : hematuria, RBC casts, proteinuria, rapid doubling of creatinine. RPGN (pauci-immune crescentic GN) : identical to GPA. Glomerulonephritis is less frequent and milder.
Unique Features Proptosis from retro-orbital pseudotumor. Pure pulmonary-renal syndrome without granulomas or asthma. Marked peripheral eosinophilia (>1,500/µL or >10%) , mononeuritis multiplex (75%) , eosinophilic myocarditis/cardiomyopathy (primary cause of mortality).
Induction Therapy High-dose Glucocorticoids + Rituximab (preferred) OR Cyclophosphamide.; Avacopan (oral C5a receptor antagonist) to eliminate glucocorticoid toxicity. High-dose Glucocorticoids + Rituximab OR Cyclophosphamide. Mild: Glucocorticoids.; Severe (FFS >=1): Glucocorticoids + Cyclophosphamide/Rituximab.; Refractory/Asthma: Mepolizumab (Anti-IL-5) .
- 2. Immune-Complex Small-Vessel Vasculitides
- Cryoglobulinemic Vasculitis
Pathophysiology: Precipitation of circulating cryoglobulins (cold-insoluble immunoglobulins) in small vessels. Type II and Type III Mixed Cryoglobulinemia consist of immune complexes formed by polyclonal IgG and IgM with Rheumatoid Factor (RF) activity directed against the Fc portion of IgG.
Etiology: Strongly associated with chronic Hepatitis C Virus (HCV) infection (>90% of cases) ; less commonly associated with SLE, Sjögren syndrome, or B-cell lymphoproliferative disorders.
Classic Clinical Triad (Meltzer Triad):
Palpable Purpura (predominantly on lower extremities, dependent areas).
Arthralgias / Polyarthritis (non-erosive).
Asthenia / Peripheral Neuropathy (sensorimotor polyneuropathy or mononeuritis multiplex).
Renal Involvement: Membranoproliferative Glomerulonephritis (MPGN) with subendothelial immune deposits, hematuria, RBC casts, nephrotic/nephritic syndrome.
Diagnostic Laboratory Profile:
Positive circulating serum cryoglobulins (cryocrit) .
Markedly depressed Complement C4 with normal or mildly reduced C3.
Strongly positive Rheumatoid Factor (RF) .
Positive HCV antibody and elevated HCV RNA viral load.
Skin biopsy showing leukocytoclastic vasculitis (LCV) .
Management:
Mild-to-Moderate Disease: Direct-Acting Antiviral (DAA) therapy (e.g., Sofosbuvir/Velpatasvir or Glecaprevir/Pibrentasvir) for HCV eradication leads to complete vasculitis remission.
Severe / Organ-Threatening Disease (Rapidly progressive MPGN, severe neuropathy, digital gangrene): Plasma exchange (plasmapheresis) to rapidly clear circulating cryoglobulins + Rituximab + systemic glucocorticoids, followed by DAA antiviral therapy once acute inflammation is controlled.
IgA Vasculitis (Henoch-Schönlein Purpura - HSP)
Pathophysiology: Small-vessel leukocytoclastic vasculitis mediated by tissue deposition of IgA1-dominant immune complexes in dermal postcapillary venules, intestinal vessels, and renal mesangium. Frequently preceded by an upper respiratory tract infection.
Classic Clinical Tetrad:
Palpable Purpura: Non-thrombocytopenic purpura and petechiae distributed symmetrically over the lower extremities and buttocks .
Arthralgias / Arthritis: Transient, non-migratory oligoarthritis of knees and ankles without joint destruction.
Gastrointestinal Symptoms: Colicky, postprandial abdominal pain, nausea, vomiting, melena, and risk of intussusception in children/young adults.
Renal Disease: IgA Nephropathy (Berger-like) presenting with microscopic or macroscopic hematuria, red cell casts, and proteinuria.
Diagnostics: Normal platelet count and coagulation studies (rules out thrombocytopenic purpura). Skin punch biopsy demonstrates leukocytoclastic vasculitis with prominent granular perivascular IgA and C3 deposition on direct immunofluorescence (DIF) .
Management: Supportive care, hydration, and NSAIDs for mild disease and arthralgias. Systemic glucocorticoids (Prednisone 1 mg/kg/day) for severe abdominal pain or progressive glomerulonephritis.