Incubation period and sources of exposure for cutaneous Mycobacterium marinum infection: case report and review of the literature.

The diagnosis of cutaneous Mycobacterium marinum infection is often delayed for months after presentation, perhaps because important clinical clues in the patient's history are frequently overlooked. Knowledge of the incubation period allows the clinician to target questions about the patient's history. Prompted by a case with a prolonged incubation period, we sought to determine more precisely the incubation period of M. marinum infection. The MEDLINE database for the period 1966-1996 was searched for information regarding incubation period and type of exposure preceding M. marinum infection. Ninety-nine articles were identified, describing 652 cases. Forty cases had known incubation periods (median, 21 days; range, 5-270 days). Thirty-five percent of cases had an incubation period > or =30 days. Of 193 infections with known exposures, 49% were aquarium-related, 27.4% were related to fish or shellfish injuries, and 8.8% were related to injuries associated with saltwater or brackish water. Because the incubation period for cutaneous M. marinum infection can be prolonged, patients with atypical cutaneous infections should be questioned about high-risk exposures that may have occurred up to 9 months before the onset of symptoms.