MKSAP Quiz: 1-month history of malaise, myalgia, weight loss

A 65-year-old man is evaluated for a 1-month history of progressive malaise, myalgia, a 3.6-kg (8.0-lb) weight loss, and numbness and weakness of the right foot; left testicular pain for 1 week; and a painful rash on his legs for 2 days. Following a physical exam, lab studies, and other tests, what is the most likely diagnosis?


A 65-year-old man is evaluated for a 1-month history of progressive malaise, myalgia, a 3.6-kg (8.0-lb) weight loss, and numbness and weakness of the right foot; left testicular pain for 1 week; and a painful rash on his legs for 2 days. He was diagnosed 2 months ago with hypertension, for which he takes hydrochlorothiazide.

On physical examination, temperature is 37.2 °C (99.0 °F), and blood pressure is 165/90 mm Hg. The left testicle is tender. Small necrotic ulcers are noted on the legs. Numbness of the right lateral ankle and calf is noted, as well as weakness of right foot plantar flexion.

Laboratory studies:

Erythrocyte sedimentation rate 100 mm/h
Hemoglobin 10 g/dL (100 g/L)
Leukocyte count 13,000/µL (13 × 109/L)
Platelet count 430,000/µL (430 × 109/L)
Creatinine 1.7 mg/dL (150.3 µmol/L)
ANCA Negative
Urinalysis Normal

Renal angiogram shows microaneurysms of the renal arteries. A deep skin biopsy (deep dermis and subcutis) shows panmural inflammation with necrosis of a medium-sized artery.

Which of the following is the most likely diagnosis?

A. Giant cell arteritis
B. IgA vasculitis
C. Microscopic polyangiitis
D. Polyarteritis nodosa


MKSAP Answer and Critique

The correct answer is D. Polyarteritis nodosa. This content is available to MKSAP 18 subscribers as Question 19 in the Rheumatology section. More information about MKSAP is available online.

The most likely diagnosis is polyarteritis nodosa (PAN), a vasculitis affecting medium-sized arteries. This entity may occur in the setting of chronic hepatitis B virus infection, HIV infection, and hairy cell leukemia. The most common symptoms are constitutional, including fever, malaise, and weight loss, and neurologic symptoms such as mononeuritis multiplex. Skin rashes, including purpura and necrotic ulcers, occur in more than half of patients. Kidney involvement manifests as hypertension due to renal artery vasculitis with renal infarction, not glomerulonephritis. Orchitis, an uncommon manifestation, is usually unilateral and due to testicular artery involvement. Mesenteric vasculitis may cause abdominal pain, perforation, and bleeding. This patient has all of these findings except for mesenteric involvement. Diagnosis of PAN is best established by demonstrating necrotizing arteritis in biopsy specimens or finding characteristic medium-sized artery aneurysms and stenoses on imaging studies of the mesenteric or renal arteries. This patient's renal angiogram confirms the presence of vasculitis and skin biopsy confirms medium-vessel vasculitis, consistent with the diagnosis of PAN.

Giant cell arteritis causes myalgia and elevated erythrocyte sedimentation rate but involves large vessels usually in the head and neck area or great vessels of the chest, not medium-sized vessels. Furthermore, it usually does not involve nerves or kidneys.

IgA vasculitis can cause testicular involvement, mononeuritis, and rash (palpable purpura), but it affects small vessels and causes glomerulonephritis rather than renovascular involvement.

Microscopic polyangiitis (MPA) is an ANCA-associated vasculitis affecting small vessels. It can cause neurologic involvement and skin rash, but kidney involvement is due to glomerulonephritis rather than renal artery vasculitis. Furthermore, MPA is associated with a positive ANCA with perinuclear pattern, directed against myeloperoxidase. This patient does not have a positive ANCA or glomerulonephritis, making MPA an unlikely diagnosis.

Key Point

  • Polyarteritis nodosa is a vasculitis affecting medium-sized arteries and is characterized by constitutional and neurologic symptoms, skin rashes, and kidney involvement that is renovascular rather than glomerular in origin.