Mycobacterium ulcerans infection (Buruli ulcer)

This occurs in restricted areas of the rural tropics near rivers[md]the Congo in Zaire, the Upper Nile and Lake Kyoga in Uganda, the Nyong in the Cameroons, and in the lowland swamps of Malaysia. It is also occasionally seen in Zambia.

The patient is often a child, and in some areas is likely to be a woman, who presents with a painless, small, well demarcated, indurated swelling, attached to the skin, but not to deeper tissues. It is almost always single and on the limbs, and is often near a joint, although the site is more variable in young children. There is little pain or tenderness, little or no fever, and the regional lymph nodes are not enlarged. The lesion grows, the skin over it desquamates, becomes pigmented, and then breaks down to form a chronic expanding ulcer, with a necrotic base, and edges which may be undermined 5 to 15 cm. Secondary infection occurs, and a foul slough forms. Satellite ulcers may appear, but metastatic spread is rare. Some ulcers remain unchanged for weeks; others cover much of a limb, or the trunk, in a few weeks. Untreated ulcers commonly heal spontaneously, with much scarring and severe contractures.

BURULI ULCER THE DIAGNOSIS is suggested by the the appearance of the swelling and the ulcer, the absence of lymph node enlargement, and the failure to respond to tropical ulcer therapy (31.2).

SPECIAL TESTS. Look for AAFB in the chronic base of the ulcer, and send material for culture. M. ulcerans grows on the media used for M. tuberculosis, but only at 33[de]C.

THE DIFFERENTIAL DIAGNOSIS in the nodule stage includes: boils, foreign body granulomas, and low-grade fibrosarcomas. In the ulcer stage it includes: tropical, mycotic, parasitic, and malignant ulcers.

CHEMOTHERAPY. M. ulcerans is sensitive in vitro to streptomycin, clofazimine, and rifampicin, but these drugs have little clinical effect. Even so, give them to cover surgery.

TREATMENT. Excise early lesions, if possible with primary closure (unlikely).

If the lesion is ulcerated, control pyogenic infection with antibiotics, and irrigate with saline. Excise all diseased tissue, and graft (57.1). If you fail to remove all diseased tissue, the graft will fail, and healing will be slow, with much scarring.