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Borderline Leprosy: The manifestations in borderline tuberculoid leprosy (BT), borderline leprosy (BB), and borderline lepromatous leprosy (BL) are intermediate between the two extremes of tuberculoid leprosy (TT) and lepromatous leprosy (LL).
In borderline tuberculoid leprosy (shown here), the skin lesions consist of scattered hypopigmented hairless plaques. The lesions are fewer in number and their distribution is less symmetrical than LL. The nerves are thickened but their involvement is less severe than TT. An individual patient with borderline leprosy may migrate towards either end of the spectrum in the course of their disease.
Microscopically, borderline tuberculoid leprosy shows granulomas associated with peripheral lymphocytes along neurovascular bundles and occasional Langhans giant cells. In some cases, granulomas are indistinct and the findings are limited to lymphocytes along superficial vascular plexuses (as shown here). In such cases, high index of suspicion is required to make the right diagnosis.
In borderline tuberculoid leprosy (shown here), the skin lesions consist of scattered hypopigmented hairless plaques. The lesions are fewer in number and their distribution is less symmetrical than LL. The nerves are thickened but their involvement is less severe than TT. An individual patient with borderline leprosy may migrate towards either end of the spectrum in the course of their disease.
Microscopically, borderline tuberculoid leprosy shows granulomas associated with peripheral lymphocytes along neurovascular bundles and occasional Langhans giant cells. In some cases, granulomas are indistinct and the findings are limited to lymphocytes along superficial vascular plexuses (as shown here). In such cases, high index of suspicion is required to make the right diagnosis.