Primary macular amyloidosis: An ultrastructural approach to diagnosis

Seven cases of primary macular amyloidosis were studied on skin biopsies. T he Congo red stain was positive only in three cases, whereas the ultrastruc tural observation allowed for the detection of amyloid deposits in all biop sies. Fibrillary degeneration of basal keratynocytes was occasionally obser ved, and regressive changes of keratynocytes and dermal nerve bundles presu mably related to the intensity of the scratch trauma were detected in one c ase. In six biopsies mast cell profiles exhibiting various degrees of degra nulation were detected in the dermis. Melanosome aggregates were also obser ved consistently in dermal macrophages and occasionally in Schwann cells. A variable degree of structural alteration was observed in dermal unmyelinat ed nerve fibers. Even if the intimate mechanism of amyloid deposition was n ot explained by the ultrastructural study, this approach is a useful instru ment in the differential diagnosis of cutaneous macular hyperpigmented lesi ons.