A 53-year-old man comes to the emergency department because of a 1-month history of cough productive of small amounts of blood-tinged sputum. During this time, he has also developed fatigue, myalgia, and shortness of breath on exertion. He has had a 4-lb (2-kg) weight loss over the past 2 months. He has no personal history of serious illness. His mother has systemic lupus erythematosus. His temperature is 37.2°C (99.0 °F), pulse is 98/min, respirations are 22/min, and blood pressure is 152/98 mm Hg. Diffuse rhonchi are heard on auscultation of the chest bilaterally. There are multiple palpable, erythematous, nonblanching lesions on the lower extremities bilaterally. Laboratory studies show: Leukocyte count 12,300 cells/mm3 Platelet count 400,000 cells/mm3 Erythrocyte sedimentation rate 83 mm/hr Serum Creatinine 2.1 mg/dL Antinuclear antibody 1:40 Urine Protein 3+ Blood 2+ RBC casts numerous A biopsy specimen of the skin shows inflammation of the arterioles and capillaries without granuloma formation. Further evaluation of this patient is most likely to show which of the following findings?

Myeloperoxidase antineutrophil cytoplasmic antibody

Anti-glomerular basement membrane antibodies

Anti-double stranded DNA antibodies

A 72-year-old man comes to the physician because of a 6-month history of intermittent dull abdominal pain that radiates to the back. He has smoked one pack of cigarettes daily for 50 years. His blood pressure is 145/80 mm Hg. Abdominal examination shows generalized tenderness and a pulsatile mass in the periumbilical region on deep palpation. Further evaluation of the affected blood vessel is most likely to show which of the following?

Fragmentation of elastic tissue in the tunica media

Obliterative inflammation of the vasa vasorum

Formation of giant cells in the tunica media

Necrotizing inflammation of the entire vessel wall

Accumulation of foam cells in the tunica intima

A 67-year-old man presents with an excruciatingly painful tongue lesion. He says the lesion was preceded by an intermittent headache for the past month that localized unilaterally to the left temple and occasionally radiates to the right eye. The tongue lesion onset acutely and has been present for a few days. The pain is constant. His past medical history is relevant for hypertension and recurrent migraines. Current medications include captopril. On physical examination, multiple knot-like swellings are seen on the left temple. Findings from an inspection of the oral cavity are shown in the exhibit (see image). Laboratory findings are significant for the following: Hemoglobin 12.9 g/dL Hematocrit 40.7% Leukocyte count 5500/mm3 Neutrophils 65% Lymphocytes 30% Monocytes 5% Mean corpuscular volume 88.2 μm3 Platelet count 190,000/mm3 Erythrocyte sedimentation rate 45 mm/h Which of the following is the next best step in the management of this patient?

High-dose systemic corticosteroids

A 75-year-old woman comes to the physician because of generalized weakness for 6 months. During this period, she has also had a 4-kg (8.8-lb) weight loss and frequent headaches. She has been avoiding eating solids because of severe jaw pain. She has hypertension and osteoporosis. She underwent a total left-sided knee arthroplasty 2 years ago because of osteoarthritis. The patient does not smoke or drink alcohol. Her current medications include enalapril, metoprolol, low-dose aspirin, and a multivitamin. She appears pale. Her temperature is 37.5°C (99.5°F), pulse is 82/min, and blood pressure is 135/80 mm Hg. Physical examination shows no abnormalities. Laboratory studies show: Hemoglobin 10 g/dL Mean corpuscular volume 87 μm3 Leukocyte count 8,500/mm3 Platelet count 450,000/mm3 Erythrocyte sedimentation rate 90 mm/h Which of the following is the most appropriate next step in management?

Oral prednisone and temporal artery biopsy

Intravenous methylprednisolone only

Intravenous methylprednisolone and temporal artery 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?

Post-streptococcal glomerulonephritis

Vasculitides classification for USMLE Step 3: High-Yield Internal Medicine Lessons

Vasculitides Classification - Vessel Size Matters

Vasculitides Classification by Vessel Size and Biopsy Type

Large-Vessel
- Giant Cell Arteritis (Temporal)
- Takayasu Arteritis
Medium-Vessel
- Polyarteritis Nodosa (PAN)
- Kawasaki Disease
- Buerger Disease
Small-Vessel
- ANCA-Associated: GPA, MPA, EGPA
- Immune Complex: IgA Vasculitis (HSP), Cryoglobulinemic

⭐ ANCA Serology is Key

c-ANCA/PR3: Granulomatosis with Polyangiitis (GPA)

p-ANCA/MPO: Microscopic Polyangiitis (MPA), Eosinophilic Granulomatosis with Polyangiitis (EGPA)

Large-Vessel Vasculitides - The Big Guns

Giant Cell (Temporal) Arteritis
- Elderly patients (age > 50), affects carotid artery branches.
- Presents with headache, jaw claudication, vision loss (amaurosis fugax).
- Strongly associated with Polymyalgia Rheumatica (PMR).
- Dx: ↑ ESR/CRP; temporal artery biopsy is gold standard.
⭐ High risk of irreversible blindness due to ophthalmic artery occlusion. Start high-dose steroids immediately if suspected; do not wait for biopsy results.
Takayasu Arteritis
- Younger patients (age < 40), typically Asian women.
- Affects aortic arch & its primary branches.
- "Pulseless disease": weak upper extremity pulses, blood pressure discrepancies.
- Dx: Angiography shows stenosis/occlusion.

Medium-Vessel Vasculitides - Middle-of-the-Road Mayhem

Polyarteritis Nodosa (PAN)
- Segmental, necrotizing vasculitis sparing pulmonary arteries.
- Strongly associated with Hepatitis B/C.
- Features: Renal failure (ischemia, not GN), hypertension, myalgias, livedo reticularis.
- Angiography reveals microaneurysms ("beads-on-a-string").
Kawasaki Disease
- Affects children < 5 years old.
- 📌 CRASH & Burn (Fever > 5 days):
  - Conjunctivitis (bilateral, non-exudative)
  - Rash (polymorphous)
  - Adenopathy (cervical)
  - Strawberry tongue/lip changes
  - Hand/foot erythema & edema

⭐ The most feared complication of Kawasaki Disease is coronary artery aneurysm. Treat urgently with IVIG and high-dose aspirin to prevent thrombosis.

Small-Vessel Vasculitides - It's the Little Things

Primarily affects arterioles, capillaries, and venules. Divided into ANCA-associated and immune complex-mediated types.

ANCA-Associated Vasculitides (AAV): Pauci-immune (little to no immune deposits on biopsy).
- Granulomatosis with Polyangiitis (GPA):
  - Affects upper/lower respiratory tract & kidneys.
  - Labs: c-ANCA (anti-PR3).
  - 📌 GPA = "C" disease: C-ANCA, Chronic sinusitis, Cavitary lung lesions, Crescentic GN.
- Microscopic Polyangiitis (MPA):
  - Affects lungs & kidneys; no granulomas or nasopharyngeal involvement.
  - Labs: p-ANCA (anti-MPO).
- Eosinophilic GPA (EGPA/Churg-Strauss):
  - Asthma, sinusitis, and prominent peripheral eosinophilia.
  - Labs: p-ANCA (anti-MPO) in ~40%.
Immune Complex-Mediated:
- IgA Vasculitis (Henoch-Schönlein Purpura):
  - Most common in children, often after URI.
- Cryoglobulinemic Vasculitis:
  - Associated with Hepatitis C.
  - Triad: palpable purpura, arthralgias, weakness.

⭐ IgA Vasculitis (HSP) is the most common childhood vasculitis, classically presenting with the tetrad of palpable purpura (on buttocks/legs), arthritis, abdominal pain, and renal disease (IgA nephropathy).

High‑Yield Points - ⚡ Biggest Takeaways

Large-vessel vasculitis (e.g., Giant Cell Arteritis, Takayasu) involves the aorta and its major branches.

Medium-vessel vasculitis (e.g., Polyarteritis Nodosa, Kawasaki) causes aneurysms; PAN spares the lungs.

Kawasaki disease is critical in children due to the risk of coronary artery aneurysms.

Small-vessel vasculitides are divided into ANCA-associated and immune complex-mediated types.

GPA (Wegener's) is c-ANCA positive, with a classic triad of sinus, lung, and kidney involvement.

EGPA (Churg-Strauss) is characterized by asthma, eosinophilia, and p-ANCA positivity.

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