Immunohistochemical studies of amyloid P component in disorders of cutaneous elastic tissue

SUMMARY Distinctive abnormalities in the immunofluorescence/immunoperoxidase staining pattern of dermal elastic tissue were observed with antibodies to serum amyloid P component (SAP) in solar elastosis, lupus erythematosus, porphyria and pseudoxanthoma elasticum, and resembled those seen with conventional elastic tissue stains. Electron microscopy of elastotic skin revealed the presence of vacuotated disintegrating elastic fibres. Islands of amorphous microfibrillar material were surrounded by a rim of specific staining with anti-SAP, indicating an elastic tissue origin; there was no evidence for the involvement of collagen fibres in the formation of elastotic material. Immunohistochemical staining with anti-SAP, a marker for elastic fibre microfibrils, is a useful method for the investigation of cutaneous elastic tissue disorders.