Unexpected diminished innervation of epidermis and dermoepidermal junction in lichen amyloidosus

Lichen amyloidosus is a localized, chronic, pruritic skin disease characterized by deposition of amyloid in the papillary dermis. The pathogenesis of the pruritus of lichen amyloidosus is largely unknown.

To determine any change in the nerve fibre density in lichen amyloidosus lesions as an explanation for itch.

Using an antibody to protein gene product (PGP) 9.5, the immunohistochemical analysis of the skin biopsies of 30 Hispanic patients with clinicopathologically proven lichen amyloidosus and of 11 healthy Hispanic controls matched for age, sex and site was performed.

Unexpectedly, the mean amount of PGP9.5 stain, a measure for nerve fibre amount, for the healthy controls was higher than the lichen amyloidosus group both in the epidermis (P < 0.0019) and dermoepidermal junction (P < 0.0064). No change was observed in the papillary dermis. Furthermore, the proportion of area covered by PGP9.5 showed a significant decrease in the epidermis (P < 0.0024) and dermoepidermal junction (P < 0.0075) in lichen amyloidosus compared with healthy controls. Age, gender and body site were found not to be influencing factors in nerve fibre amounts in lichen amyloidosus samples.

We speculate that the severe pruritus observed in lichen amyloidosus might be the result of the hypersensitivity of the remaining nerve fibres as a response to an unexplained neurodegeneration of the absent nerve fibres.