lepromatous

Lepromatous leprosy is the multibacillary form of Hansen's disease characterized by extensive skin involvement and a high burden of Mycobacterium leprae in tissues. It represents the far end of the clinical spectrum, reflecting poor cell-mediated immunity. In this form, skin lesions are numerous and bilateral, and skin smears typically show abundant acid-fast bacilli.

Clinically, lesions are often symmetric and include patches, nodules, and plaques. The skin is thickened and infiltrated, and facial changes such as leonine facies may occur. Nasal collapse and other mucosal involvement can develop. Nerve involvement tends to be diffuse rather than focal, and peripheral nerve function loss may progress more gradually. Systemic symptoms are generally mild, but dissemination to eyes, testes, or other organs can occur.

Diagnosis is supported by skin-smear (slit-skin smear) showing numerous acid-fast bacilli and by histopathology demonstrating foamy macrophages filled with bacilli (Virchow cells). The lepromin skin test is typically negative in lepromatous disease. The combination of clinical picture and bacteriological findings confirms the diagnosis.

Treatment and prognosis: Multidrug therapy (MB-MDT) for lepromatous leprosy typically includes rifampicin, dapsone, and clofazimine for about 12 months. Clofazimine can cause skin discoloration; dapsone and rifampicin have other potential adverse effects. Lepra reactions, especially erythema nodosum leprosum, may occur and require management with anti-inflammatory or immunomodulatory therapy. After MDT, infectiousness decreases, but nerve damage can be permanent, underscoring the importance of early diagnosis and treatment.

Transmission and public health: transmission occurs mainly through prolonged close contact with an untreated person and is reduced substantially after initiating MDT. Public health programs aim to detect cases early and prevent disability; there is no widely used leprosy vaccine, though BCG provides some protection.