Borderline tuberculoid leprosy following BCG vaccination. A case report.

Borderline tuberculoid leprosy was diagnosed clinically and histologically in a four year-old boy about 6 months after intradermal vaccination with BCG. His mother reported that a lesion began to appear above the vaccination site on the arm 2 weeks after the vaccination, and a second lesion appeared on the chin 2 months later. Responses in the lymphocyte transformation test to sonicated Mycobacterium leprae, BCG, and to PPD were consistent with a tuberculoid leprosy infection. Precipitation of BT leprosy by intradermal BCG infection may possibly represent the overcoming of a phase of primary suppression in an individual who might otherwise have progressed toward lepromatous leprosy. The implications of this hypothesis for the planning of a controlled trial of an anti-leprosy vaccine are discussed.