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 50-year-old man comes to the physician for the evaluation of recurrent episodes of chest pain, difficulty breathing, and rapid heart beating over the past two months. During this period, he has had a 4-kg (8.8-lb) weight loss, malaise, pain in both knees, and diffuse muscle pain. Five years ago, he was diagnosed with chronic hepatitis B infection and was started on tenofovir. His temperature is 38°C (100.4°F), pulse is 110/min, and blood pressure is 150/90 mm Hg. Cardiopulmonary examination shows no abnormalities except for tachycardia. There are several ulcerations around the ankle and calves bilaterally. Laboratory studies show: Hemoglobin 11 g/dL Leukocyte count 14,000/mm3 Erythrocyte sedimentation rate 80 mm/h Serum Perinuclear anti-neutrophil cytoplasmic antibodies negative Hepatitis B surface antigen positive Urine Protein +2 RBC 6-7/hpf Which of the following is the most likely diagnosis?

Granulomatosis with polyangiitis

A 71-year-old woman comes to the physician because of sudden loss of vision in her right eye for 15 minutes that morning, which subsided spontaneously. Over the past 4 months, she has had fatigue, a 4-kg (8.8-lb) weight loss, and has woken up on several occasions at night covered in sweat. She has had frequent headaches and pain in her jaw while chewing for the past 2 months. She does not smoke or drink alcohol. Her temperature is 37.5°C (99.5°F), pulse is 88/min, and blood pressure is 118/78 mm Hg. Examination shows a visual acuity of 20/25 in the left eye and 20/30 in the right eye. The pupils are equal and reactive. There is no swelling of the optic discs. Her hemoglobin concentration is 10.5 g/dL, platelet count is 420,000/mm3, and erythrocyte sedimentation rate is 69 mm/h. The patient's condition puts her at the greatest risk of developing which of the following complications?

Rapidly progressive glomerulonephritis

Internal carotid artery stenosis

A 54-year-old man comes to the physician because of a cough with blood-tinged sputum for 1 week. He also reports fever and a 5-kg (11 lb) weight loss during the past 2 months. Over the past year, he has had 4 episodes of sinusitis. Physical examination shows palpable nonblanching skin lesions over the hands and feet. Examination of the nasal cavity shows ulceration of the nasopharyngeal mucosa and a depressed nasal bridge. Oral examination shows a painful erythematous gingival enlargement that bleeds easily on contact. Which of the following is the most likely cause of the patient's symptoms?

Metalloprotease enzyme deficiency

Malignant myeloid cell proliferation

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

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

Vasculitis for USMLE Step 2 CK: High-Yield Pathology Lessons

Vasculitis Basics - Vessel Wall Woes

Inflammation & necrosis of blood vessel walls, leading to downstream tissue ischemia and potential organ damage.
Pathogenesis is often immune-mediated via immune complexes, anti-neutrophil cytoplasmic antibodies (ANCAs), or pathogenic T-cells.
Classified by the predominant vessel size involved.

⭐ Most vasculitides present with nonspecific constitutional symptoms like fever, myalgia, arthralgia, and fatigue.

Histology of blood vessel wall layers

Large-Vessel - Aortic Arch Archons

Giant Cell (Temporal) Arteritis
- Age > 50; affects branches of carotid artery.
- Symptoms: Unilateral headache, jaw claudication, tender temporal artery.
- Assoc: Polymyalgia Rheumatica (PMR).
- Path: Granulomatous inflammation, fragmented internal elastic lamina; ↑ ESR, CRP.
- Tx: High-dose corticosteroids STAT to prevent blindness.
Takayasu Arteritis
- Age < 50 (typically young Asian women).
- Symptoms: "Pulseless disease" → weak upper extremity pulses, fever, night sweats, arthritis.
- Path: Granulomatous thickening of aortic arch & proximal great vessels.

⭐ High-Yield: Unilateral vision loss in GCA is an ophthalmic emergency due to anterior ischemic optic neuropathy (AION). It can become bilateral and irreversible within hours.

Giant Cell Arteritis Histopathology

Medium-Vessel - Beaded & Fiery

Polyarteritis Nodosa (PAN)
- Segmental, transmural necrotizing vasculitis.
- Associated with Hepatitis B/C in ~30% of cases.
- Affects renal & visceral arteries; spares pulmonary circulation.
- Creates microaneurysms, giving a "string-of-pearls" or "rosary bead" appearance on angiography.
- Presents with fever, abdominal pain, myalgias, and hypertension.
Kawasaki Disease
- Affects Asian children < 4 years old.
- 📌 CRASH & Burn: Conjunctivitis, Rash, Adenopathy, Strawberry tongue, Hand-foot changes + Fever >5 days.
⭐ High risk of coronary artery aneurysms. Treat urgently with IVIG and aspirin.

Kawasaki Disease: Symptoms and Cardiac Complications

Small-Vessel - ANCA's Angry Armada

Pauci-immune necrotizing vasculitis: Characterized by little to no immune complex deposition on vessel walls. All are associated with Anti-Neutrophil Cytoplasmic Antibodies (ANCA).

Feature	Granulomatosis w/ Polyangiitis (GPA)	Microscopic Polyangiitis (MPA)	Eosinophilic GPA (EGPA)
ANCA	c-ANCA (anti-PR3) >80%	p-ANCA (anti-MPO) ~70%	p-ANCA (anti-MPO) ~50%
Key Organs	Upper respiratory (sinusitis, otitis), Lower respiratory (nodules, hemoptysis), Kidneys (RPGN)	Lungs, Kidneys (RPGN). No nasopharyngeal involvement.	Lungs, Heart, Skin, Nerves (mononeuritis multiplex). Late-stage renal.
Histology	Granulomatous inflammation	Non-granulomatous	Eosinophilic infiltrates, granulomas
Unique	Nasopharyngeal destruction	No granulomas	Allergic rhinitis, asthma, peripheral eosinophilia

⭐ ANCA vasculitides cause a pauci-immune (literally "few-immunes") glomerulonephritis. Biopsy shows necrotizing glomerulonephritis with crescents but lacks significant Ig/C3 deposition on immunofluorescence.

Pauci-immune crescentic glomerulonephritis histology

High‑Yield Points - ⚡ Biggest Takeaways

Giant Cell Arteritis: Most common vasculitis in adults >50; presents with headache, jaw claudication, and risk of blindness. Associated with high ESR.

Kawasaki Disease: Affects children <5; presents with fever & CRASH symptoms. Can lead to coronary artery aneurysms.

Polyarteritis Nodosa: Necrotizing vasculitis of medium arteries, strongly associated with Hepatitis B, and characteristically spares the lungs.

GPA (Wegener's): Triad of sinus, lung, and kidney disease; positive for c-ANCA.

Thromboangiitis Obliterans: Seen in heavy smokers; can lead to gangrene of digits.

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Vasculitis