A previously healthy man returns from Arizona with fever, dry cough and erythema nodosum over the shins. Chest radiograph shows a thin-walled cavity in the upper lobe. Lung biopsy reveals large thick-walled spherules, 20 to 100 micrometres in diameter, containing endospores. The diagnosis is:
- A Tuberculous cavity with caseation
- B Pulmonary coccidioidomycosis ✓
- C Chronic pulmonary histoplasmosis
- D Paracoccidioidomycosis
Correct answer: B. Pulmonary coccidioidomycosis
Explanation
In human tissue Coccidioides exists exclusively as a spherule, a large double-walled structure filled with endospores, and seeing it confirms coccidioidomycosis acquired from the deserts of the southwestern United States. Erythema nodosum reflects a good host immune response. Paracoccidioides instead appears as a mother cell with multiple peripheral buds, and Histoplasma forms tiny intracellular yeasts, so both are excluded by the biopsy finding.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.