[Hansen's Disease]

Hansen's disease is a chronic infection of the skin and peripheral nerves caused by Mycobacterium leprae and Mycobacterium lepromatosis. Recently, only a few new cases have been reported in Japan. Diagnosis is based on the demonstration of the bacillus through skin smears, histopathology, or polymerase chain reaction, as well as other clinical and laboratory findings. Nerve conduction studies can detect subclinical neuropathy. Clinical classification is determined by variations in the host's cell-mediated immunity. The World Health Organization divides leprosy into paucibacillary (PB) and multibacillary (MB) forms. Ridley and Jopling classified the disease along a continuous spectrum from tuberculoid to lepromatous. Leprosy reactions, both type 1 and type 2, can lead to rapid nerve deterioration, necessitating immediate anti-inflammatory treatment and the continuation of multidrug therapy. The standard multidrug therapy regimen includes dapsone, rifampicin, and clofazimine, with typical durations of 6 months for PB and 12 months for MB. Peripheral nerve damage is irreversible once it occurs, making prevention the most effective strategy. Neuropathic pain is treated with agents such as pregabalin and amitriptyline. Rehabilitation is provided for muscle atrophy, and orthoses and prostheses are used to address deformities of the fingers and toes as well as limb deficiencies. Collaboration between dermatologists and physiatrists is essential.