A 30-year-old African American woman has a 2-month history of nonproductive cough and a painful skin eruption in the lower extremities. She denies fever or weight loss. Physical examination shows several nontender raised plaques around the nares and scattered similar plaques around the base of the neck. In the lower extremities she has several erythematous tender nonulcerated nodules, measuring up to 4 cm in diameter. Chest x-ray reveals bilateral hilar adenopathy and a streaky interstitial density in the right upper lobe.
What is the best way to establish a histo-logical diagnosis?
A. Punch biopsy of one of the plaques on the neckThis patient probably has sarcoidosis; rarely tuberculosis or granulomatous fungal infections can cause the same syndrome. The painful nodules on the legs represent erythema nodosum, a hypersensitivity reaction associated with this patient’s illness. Erythema nodosum can be associated with sarcoidosis, TB, inflammatory bowel disease, several other infectious processes or can be idiopathic. Biopsy of one of the tender nodules would reveal a nonspecific panniculitis (inflammation of the subcutaneous fat) and would not be helpful diagnostically. Biopsy of one of the plaques, however, would reveal noncaseating granulomas characteristic of sarcoidosis and would be helpful in ruling out the less likely infectious pathogens. Skin biopsy is safer and less expensive than an invasive procedure such as mediastinoscopy. In the absence of sputum production, fever, or weight loss, AFB and fungal studies are unlikely to be productive. The serum ACE assay is nonspecifically elevated in many systemic granulomatous diseases and plays a minor role in the assessment and management of a patient with sarcoidosis.