An 8-year-old girl had a visibly enlarged submandibular lymph node and a reddish, spongy swelling of the gingiva in the upper right canine region. Culturing of the gingival tissue resulted in the isolation of Mycobacterium chelonae, and the patient showed a specific skin hypersensitivity reaction to M. chelonae sensitin. The gingival swelling disappeared spontaneously without scarring within 5 weeks after the biopsy. There was no recurrence intraorally during the 2 1/2-year follow-up, the generalized lymphadenopathy subsided within 2 years, and at the last visit, the submandibular lymph node could barely be felt. The patient received no medication during the course of the disease. A tortoise held as a pet by the girl could possibly have been the source of infection since iatrogenic sources of infection could be excluded.