A 45-year-old man with asthma comes to the physician because of a 1-month history of progressively worsening shortness of breath and cough. He also has a history of chronic sinusitis and foot drop. Current medications include an albuterol inhaler and inhaled corticosteroid. Physical examination shows diffuse wheezing over both lung fields and tender subcutaneous nodules on both elbows. Laboratory studies show a leukocyte count of 23,000/mm3 with 26% eosinophils and a serum creatinine of 1.7 mg/dL. Urine microscopy shows red blood cell casts. Which of the following is the most likely diagnosis in this patient?

Eosinophilic granulomatosis with polyangiitis

Granulomatosis with polyangiitis

A previously healthy 4-year-old boy is brought to the physician by his parents because he has had a fever, diffuse joint pain, and a rash on his abdomen for the past week. Acetaminophen did not improve his symptoms. He emigrated from China with his family 2 years ago. He attends daycare. His immunization records are not available. His temperature is 38.5°C (101.3°F), pulse is 125/min, and blood pressure is 100/60 mm Hg. Examination shows polymorphous truncal rash. The eyes are pink with no exudate. The tongue is shiny and red, and the lips are cracked. The hands and feet are red and swollen. There is right-sided anterior cervical lymphadenopathy. Which of the following is the most appropriate next step in management?

HHV-6 immunoglobulin M (IgM) detection

Antistreptolysin O titer measurement

A 17-year-old boy is brought to the physician because of swelling of his face and legs for 5 days. He immigrated to the United States from Korea with his family 10 years ago. He has been healthy except for an episode of sore throat 2 weeks ago. His younger sister has type 1 diabetes mellitus. His temperature is 37°C (98.6°F), pulse is 90/min, and blood pressure is 145/87 mm Hg. Examination shows periorbital edema and 3+ pitting edema of the lower extremities. Laboratory studies show: Hemoglobin 13.9 g/dL Leukocyte count 8,100/mm3 Serum Glucose 78 mg/dL Albumin 2.4 g/dL Hepatitis B surface antigen positive Hepatitis B surface antibody negative Complement C4 decreased Urine Blood negative Protein 4+ Glucose negative Protein/creatinine ratio 8.1 (N ≤ 0.2) Further evaluation is most likely to show which of the following additional findings?

Subepithelial deposits on renal biopsy

Normal-appearing glomeruli on renal biopsy

Antineutrophil cytoplasmic antibody level in serum

Eosinophilic nodules on renal biopsy

A 45-year-old man comes to the physician because of fatigue and joint pain for 8 months. He has pain in both knees, both elbows, and diffuse muscle pain. He does not have dyspnea. He also had several episodes of a nonpruritic rash on his lower extremities. Eight years ago, the patient was diagnosed with hepatitis C. His temperature is 37.9°C (100.2°F), pulse is 90/min, and blood pressure is 140/90 mm Hg. Examination of the lower extremities shows raised purple papules that do not blanch when pressure is applied. Cardiopulmonary examination shows no abnormalities. Laboratory studies show: Hemoglobin 13.9 g/dL Leukocyte count 8,500/mm3 Platelets 160,000/mm3 Serum Creatinine 1.1 mg/dL ALT 123 U/L AST 113 U/L Further evaluation of this patient is most likely to show which of the following findings?

Granulomatous inflammation of vessels

Elevated perinuclear anti-neutrophil cytoplasmic antibodies

A 62-year-old man presents to the emergency department with hematuria and hemoptysis that started in the morning. He notes that he has had frequent lung infections throughout his adult life, the most recent being 2 weeks ago. He also mentions that he has had hematuria twice before but never as severe as he is having currently. His medical history is otherwise non-significant, and his only medication is acetaminophen as needed. His blood pressure is 136/92 mm Hg, heart rate is 86/min, respiratory rate is 16/min, and temperature is 37.0°C (98.6°F). Chest radiography shows a resolving right middle lobe airspace opacity. His initial laboratory tests are notable for elevated erythrocyte sedimentation rate and C-reactive protein level. While in the examination room, the patient develops a spontaneous nosebleed. What is the most likely diagnosis?

Granulomatosis with polyangiitis

Post-streptococcal glomerulonephritis

A 40-year-old woman comes to the emergency department because of difficulty walking for the past 4 hours. She first noticed her symptoms after getting up this morning and her foot dragging while walking. She feels tired. She has a history of chronic sinusitis. Six months ago, she was diagnosed with asthma. Current medications include an albuterol inhaler and inhaled corticosteroids. Her temperature is 38.9°C (102°F), pulse is 80/min, and her blood pressure is 140/90 mm Hg. Auscultation of her lungs shows diffuse wheezing over bilateral lung fields. Physical examination shows tender subcutaneous nodules on the extensor surfaces of the elbows. There are palpable, non-blanching erythematous lesions on both shins. Dorsiflexion of the right foot is impaired. Sensation to pinprick, light touch, and vibration is decreased over the ulnar aspect of the left forearm. Laboratory studies show: Hemoglobin 11.3 g/dL Leukocyte count 24,500 Segmented neutrophils 48% Eosinophils 29% Lymphocytes 19% Monocytes 4% Platelet count 290,000/mm3 Serum Urea nitrogen 32 mg/dL Creatinine 1.85 mg/dL Urine Blood 2+ Protein 3+ Which of the following is the most likely diagnosis in this patient?

Eosinophilic granulomatosis with polyangiitis

Granulomatosis with polyangiitis

A 32-year-old woman who recently emigrated to the USA from Japan comes to the physician because of a 3-month history of night sweats, malaise, and joint pain. During this time, she has also had a 6-kg (13-lb) weight loss. Physical examination shows weak brachial and radial pulses. There are tender subcutaneous nodules on both legs. Carotid bruits are heard on auscultation bilaterally. Laboratory studies show an erythrocyte sedimentation rate of 96 mm/h. A CT scan of the chest shows thickening and narrowing of the aortic arch. Microscopic examination of the aortic arch is most likely to show which of the following findings?

Granulomatous inflammation of the media

Fibrinoid necrosis of the intima and media

Subendothelial hyaline deposition

Subendothelial immune complex deposition

Medium vessel vasculitis for USMLE Step 1: High-Yield Internal Medicine Lessons

Medium Vessel Vasculitis - The Middle Players

Polyarteritis Nodosa (PAN):
- Affects renal & visceral arteries; spares lungs.
- Strongly associated with Hepatitis B.
- Presents with fever, myalgia, abdominal pain; "rosary sign" on angiography (aneurysms).
Kawasaki Disease: (Children < 5 years)
- 📌 CRASH & Burn: Conjunctivitis, Rash, Adenopathy, Strawberry tongue, Hand-foot changes + Fever >5 days.
- ⭐ Most feared complication is coronary artery aneurysm.
Buerger's Disease (Thromboangiitis Obliterans):
- Segmental, thrombosing vasculitis in heavy smokers.
- Can lead to gangrene and autoamputation of digits.

Polyarteritis Nodosa (PAN) - Beads on a String

Systemic necrotizing vasculitis of medium-sized muscular arteries leading to microaneurysm formation.
Key association: Hepatitis B antigen-positive in ~30% of cases (immune complex deposition).
Clinical Features:
- Constitutional: Fever, malaise, weight loss.
- Renal: Hypertension, renal ischemia (spares glomeruli).
- Neurologic: Mononeuritis multiplex (e.g., wrist/foot drop).
- Dermatologic: Livedo reticularis, tender erythematous nodules, ulcers.
- GI: Postprandial abdominal pain (mesenteric vasculitis).
Diagnosis:
- Biopsy of affected tissue (e.g., skin, nerve) shows transmural inflammation.
- Angiography reveals multiple aneurysms and stenoses.
- Typically ANCA-negative.

Renal angiogram: Polyarteritis Nodosa "beads on a string"

⭐ High-Yield: PAN characteristically spares the pulmonary arteries. The "beads on a string" appearance on renal or mesenteric angiography is a classic finding.

Treatment: High-dose corticosteroids and cyclophosphamide.

Kawasaki Disease - CRASH and Burn

Acute, necrotizing vasculitis of medium-sized vessels, primarily affecting young children (< 5 years).
Presents with fever > 5 days (the "Burn") plus ≥4 of the CRASH criteria.
📌 CRASH Mnemonic:
- Conjunctivitis: Bilateral, non-exudative.
- Rash: Polymorphous (maculopapular, morbilliform).
- Adenopathy: Cervical, unilateral.
- Strawberry tongue & other mucosal changes (e.g., cracked, red lips).
- Hand & foot changes: Erythema, edema, desquamation.

Kawasaki Disease Symptoms

⭐ High-Yield: The most feared complication is coronary artery aneurysm, which can lead to thrombosis or rupture. Echocardiography is essential for monitoring.

Diagnosis & Comparison - Tissue vs. Tubes

Tissue (Biopsy): Gold standard for Polyarteritis Nodosa (PAN).
- Shows segmental, transmural necrotizing inflammation with fibrinoid necrosis.
- Typically involves medium-sized muscular arteries; spares pulmonary circulation.
Tubes (Angiography/Imaging):
- PAN: Angiography reveals microaneurysms and stenoses in renal, mesenteric, or hepatic arteries ("rosary sign" or "beads-on-a-string"). A key alternative when biopsy is inaccessible.
- Kawasaki Disease: Diagnosis is clinical. Echocardiography is crucial to screen for and monitor coronary artery aneurysms.

Renal artery microaneurysms in polyarteritis nodosa

⭐ PAN has a strong association with Hepatitis B infection (~10-30% of cases). Always test for HBsAg.

High‑Yield Points - ⚡ Biggest Takeaways

Polyarteritis Nodosa (PAN) is a systemic necrotizing vasculitis of medium arteries that notably spares the lungs.

PAN is strongly associated with Hepatitis B in about 30% of cases.

Clinical clues for PAN include livedo reticularis, mononeuritis multiplex, and new-onset hypertension from renal artery involvement.

Kawasaki Disease is a vasculitis in children <5 years old, presenting with CRASH and Burn (fever).

The most feared complication of Kawasaki is coronary artery aneurysms.

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