Leprosy Caused by Mycobacterium lepromatosis.

Objectives: Leprosy is caused by Mycobacterium leprae or Mycobacterium lepromatosis. This study reviews literature on M lepromatosis and reports on a Mexican family with this infection.
Methods: The review included all primary studies. Family history and surveys were used to uncover the infection cluster. Genome-based differential polymerase chain reactions were designed to detect etiologic agents.
Results: Since the discovery of M lepromatosis in 2008, 154 cases of M lepromatosis infection from 11 countries in the Americas and Asia have been reported, with most cases coming from Mexico. These cases included diffuse lepromatous leprosy (DLL) and other leprosy forms. Genomes of M lepromatosis strains have lately been sequenced, revealing 3,271,694 nucleotides and approximately 15% mismatches with M leprae. The Mexican family with leprosy involved the grandfather, mother, and 2 grandsons. The index was the oldest grandson, who manifested DLL and likely contracted the infection from his maternal grandfather approximately 13 years earlier. Family surveys diagnosed DLL in the index patient's mother and borderline leprosy in his brother; both were likely infected by the index patient. M lepromatosis was identified from archived biopsies from the index patient and his mother, while M leprae was excluded.
Conclusions: M lepromatosis is a significant cause of leprosy in Mexico and requires better surveillance and control.
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