[Linear tuberculoid leprosy along the lines of Blaschko: a very rare presentation]

Leprosy continues to be present in certain regions throughout the world, and the dermatologist plays a central role in its diagnosis. Herein we report a case of tuberculoid leprosy that is atypical in terms of its linear presentation which appears to follow the lines of Blaschko.

A patient from Mayotte was referred to the neurological department for suspected tuberculoid leprosy. He was presenting a deficiency of the ulnar nerve together with neuronal hypertrophy and cutaneous involvement. Dermatological examination revealed linear hypo-aesthetic hypopigmented lesions on the arm and forearm. The atypical clinical presentation also suggested to us pigmented mosaicism or post-inflammatory pigmentation. The biopsy showed granulomatous epithelial dermatitis with perinervous involvement. Imaging examinations confirmed the presence of neuronal hypertrophy. A diagnosis of linear tuberculoid leprosy was made.

This case illustrates the need to bear in mind a diagnosis of leprosy in the event of hypopigmented lesions, even where they are linear and of Blaschkoid appearance. Several potential hypotheses may account for this particular topographical pattern.