multibacillary

Multibacillary is a medical classification most often used in the management of leprosy (Hansen's disease) to denote a form with a high bacterial load. It contrasts with paucibacillary, which indicates a low bacterial load and fewer symptoms. The MB category is primarily determined by the number of skin lesions and bacteriological data. In practice, multibacillary leprosy includes patients with more than five skin lesions or those who have a positive slit-skin smear, reflecting a high bacillary index. The disease forms typically encompassed by MB include lepromatous leprosy (LL), borderline lepromatous (BL), and sometimes borderline borderline (BB); tuberculoid forms are usually paucibacillary.

MB forms tend to present with extensive skin involvement, pronounced nerve involvement, and higher infectivity if untreated. Early recognition and treatment are important to prevent disability and reduce transmission.

Management relies on multidrug therapy tailored for MB disease, using a combination of rifampicin, dapsone, and clofazimine for a longer duration than paucibacillary regimens—commonly around 12 months under current WHO guidelines. Regular monitoring for adverse effects and nerve function is important during therapy.

See also: paucibacillary leprosy, leprosy, multidrug therapy.