Dermatomic distributions of hypopigmented macular lesions of leprosy: neural dependence of melanocytic functions.

Dermatomic analysis of the distribution of the hypopigmented patches of leprosy has revealed a pattern wherein patches are most frequent in dermatomes of the brachial plexus, decrease gradually in frequency in succeeding spinal segments and increase again in dermatomes of the lumbar plexus. The predilection of hypopigmented patches for certain dermatomes may be a reflection of easy vulnerability of the neural pigmentary mechanism and/or a reflection of selective multiplication of M. leprae in nerves of certain dermatomes, even though the organisms might have been seeded all over the body by hematogenous spread. These preliminary observations are discussed.