Colloid body formation in bullous pemphigoid

Thirty-eight biopsy specimens from 18 cases of bullous pemphigoid (BP) were observed using direct immunofluorescence (IF) techniques with fluorescein isothiocyanate (FITC)-labelled antisera against human serum factors. In addition to deposits of immunoglobulins and serum components at the basement-membrane zone (BMZ), 15 specimens from eight cases displayed homogeneous and globular fluorescent bodies in the uppermost dermis and/or the blisters when FITC-labelled antisera to human IgM and other serum factors were used. Using immunoperoxidase staining, haematoxylin/eosin (HE) and periodic acid-Schiff (PAS) staining, these immunoglobulin and/or complement-positive cell-sized bodies were shown to be slightly eosinophilic and PAS positive. Electron microscopy revealed entangled networks of microfilaments approximately 7-8 nm in diameter. These homogeneous, fibrillar bodies were histologically, immunohistologically and ultrastructurally indistinguishable from the colloid bodies found in lesional skins of lichen planus, lupus erythematosus, dermatomyositis and several other dermatoses. In BP, degenerated keratinocytes adjacent to the blister roof, may, after undergoing a filamentous change, drop off into the dermis and subsequently form homogeneous, fibrillar bodies in the uppermost dermis when reepithelization is completed.