Disseminated superficial porokeratosis with amyloid deposition.

Two patients with disseminated superficial porokeratosis (DSP) with amyloid deposition are reported. The skin lesions were distributed over both sun-exposed areas and sun-protected areas. No exacerbation by sun exposure was noted. Abundant amyloid substances were deposited at the papillary dermis, not only beneath the cornoid lamellae but also within the annular margin. The skin lesions and amyloid deposition regressed with topical application of dimethyl sulfoxide in one patient, suggesting that DSP is one of the clinical phenotypes of primary localized cutaneous amyloidosis. Another possibility is that amyloid substances are produced by poorly differentiated keratinocytes in DSP.