A 45-year-old HIV-positive male complained of persistent cough and weight loss. He has skin lesions that appear as umbilicated papules and nodules predominantly on the face, trunk, and upper extremities. Chest x-ray showed multiple bilateral nodular infiltrates. His sputum CBNAAT for tuberculosis was negative, and he has a low CD4 count. What is the probable diagnosis?

## Correct Answer: A. HIV with disseminated histoplasmosis Disseminated histoplasmosis in advanced HIV (CD4 <50 cells/µL) presents with a triad of pulmonary involvement, cutaneous manifestations, and constitutional symptoms. The key discriminating feature here is the **umbilicated papules and nodules** on the face, trunk, and upper extremities—this is pathognomonic for cutaneous histoplasmosis. The umbilication (central dimpling) mimics molluscum contagiosum but represents necrotic centers of histoplasma-infected macrophages. The bilateral nodular infiltrates on CXR reflect disseminated pulmonary involvement. Histoplasma capsulatum is endemic in parts of India (particularly in river valleys and soil-rich areas), and disseminated disease occurs almost exclusively when CD4 count falls below 50 cells/µL. The negative sputum CBNAAT rules out active TB, which would typically show cavitary lesions or upper lobe infiltrates. Histoplasmosis is diagnosed by fungal culture, histopathology showing intracellular yeast within macrophages, or antigen detection in urine/serum. Treatment requires amphotericin B followed by itraconazole maintenance therapy per Indian HIV guidelines. ## Why the other options are wrong **B. HIV with tuberculosis** — While TB is common in HIV-positive patients in India, the sputum CBNAAT is explicitly negative, ruling out active pulmonary TB. The umbilicated papules are not a feature of TB; TB typically presents with constitutional symptoms and cavitary or infiltrative lung lesions without characteristic skin lesions. This is an NBE trap using the high prevalence of TB-HIV coinfection in India. **C. HIV with disseminated cryptococcosis** — Cryptococcosis typically presents with meningitis (headache, meningeal signs) as the primary manifestation in advanced HIV, not prominent cutaneous lesions. Cryptococcal skin lesions are rare and appear as cellulitis-like lesions or nodules without umbilication. The CXR findings in cryptococcosis are usually minimal or show interstitial infiltrates, not bilateral nodular disease. Cryptococcal antigen would be positive in serum/CSF. **D. HIV with molluscum contagiosum** — Although molluscum contagiosum presents with umbilicated papules in HIV patients, it does NOT cause bilateral nodular pulmonary infiltrates or systemic constitutional symptoms like weight loss and cough. Molluscum is a superficial skin-only infection caused by a poxvirus; it does not disseminate to lungs. The presence of pulmonary disease makes this diagnosis incomplete and clinically inconsistent. ## High-Yield Facts - **Umbilicated papules and nodules** on face, trunk, and extremities in advanced HIV are pathognomonic for cutaneous histoplasmosis, not molluscum contagiosum. - **Disseminated histoplasmosis** occurs almost exclusively when CD4 count <50 cells/µL; it is endemic in parts of India (river valleys, soil-rich areas). - **Bilateral nodular infiltrates** on CXR with negative TB sputum smear/CBNAAT strongly suggests fungal dissemination (histoplasmosis) rather than TB. - **Diagnosis** of histoplasmosis: fungal culture, histopathology (intracellular yeast in macrophages), or urine/serum antigen detection. - **Treatment**: Amphotericin B induction (2 weeks) followed by itraconazole maintenance (per Indian HIV guidelines) until CD4 >100 cells/µL for ≥3 months. ## Mnemonics **HISTOPLASMOSIS in HIV (CD4 <50)** **H**igh fever, **I**nfiltrates (bilateral), **S**kin umbilicated lesions, **T**runk/face involved, **O**rgans disseminated (lungs, liver, spleen), **P**ulmonary nodules, **L**ow CD4 (<50), **A**mphotericin B (treatment), **S**erum antigen positive, **M**acrophages (intracellular yeast), **O**ccurs in endemic zones, **S**ystemic disease, **I**traconazole maintenance, **S**pread to multiple organs. **Umbilication = Histoplasmosis (not molluscum alone)** When you see umbilicated lesions + pulmonary infiltrates + low CD4 in HIV, think histoplasmosis first. Molluscum = skin only; histoplasmosis = skin + lungs + systemic. ## NBE Trap NBE pairs umbilicated papules with molluscum contagiosum to lure students into choosing option D, but the presence of bilateral pulmonary nodular infiltrates and constitutional symptoms (cough, weight loss) is the discriminating feature that points to disseminated histoplasmosis, not a skin-only infection. ## Clinical Pearl In India, disseminated histoplasmosis is an AIDS-defining illness that mimics TB clinically but is distinguished by umbilicated skin lesions and negative TB smear/CBNAAT. Early recognition and amphotericin B initiation are critical because mortality is high without treatment; always suspect histoplasmosis when TB is ruled out in advanced HIV with pulmonary disease and characteristic skin findings. _Reference: Harrison Ch. 197 (Histoplasmosis); Robbins Ch. 8 (Fungal Infections); KD Tripathi Ch. 47 (Antifungal Drugs)_