Sulfhydryl and disulfide stainings in amyloids of skin-limited and systemic amyloidoses.

Disulfide (S-S) bonds and sulfhydryl (-SH) groups in skin-limited and systemic amyloidoses in frozen and paraffin-embedded sections were examined with a thiol reagent, N-(7-dimethylamino-4-methyl-3-coumarinyl)-maleimide (DACM). In frozen sections, dermal amyloids of skin-limited amyloidoses contained a large number of S-S bonds but no -SH groups [macular amyloidosis (9 cases), lichen amyloidosis (4), and skin tumor-associated (seborrheic keratosis) amyloidosis (1)]. In contrast, amyloids of systemic amyloidoses contained no S-S bonds or -SH groups [primary and myeloma-associated amyloidoses (1 each)]. The identical results were obtained from paraffin-embedded sections in skin-limited amyloidoses [macular (31), biphasic (4), lichenoid (9) and skin tumor-associated Bowen's disease (3), seborrheic keratosis (2), solar keratosis (2), porokeratosis Mibelli (1), and basal cell epithelioma (1) amyloidoses], systemic amyloidoses [primary (3), myeloma-associated (2), and secondary (2) amyloidoses] and tumefactive amyloidoses of the tongue (2). Furthermore, amyloid-like deposits confirmed by various histochemical stainings were found in the epidermis in 27/67 cases of skin-limited amyloidoses in both frozen and paraffin sections. These intraepidermal amyloid-like deposits contained S-S bonds in all cases (27/27) and -SH groups in 10 of 27 cases. In contrast, an intraepidermal amyloid-like deposit was not observed in any systemic amyloidoses (0/9) or tumefactive amyloidoses of the tongue (2). These results showed that skin-limited amyloidoses could be differentiated from systemic amyloidoses by DACM methods (this appears to depend upon the differences of amino acid composition between skin-limited and systemic amyloidoses) and that paraffin-embedded sections were usable for DACM methods. Present study further suggests that amyloids ion skin-limited amyloidoses are, at least in part, derived from epidermal keratinocytes.