Background: Few electron microscopic studies of blister lesions in bullous amyloidosis have been reported, and the mechanism of blister formation remains to be elucidated. This study was designed to examine the nature of bullous amyloidosis ultrastructurally, and clarify the pathogenesis of blister formation.
Methods: We examined a 47-year-old woman with IgD-lambda type myeloma, suffering from bullous lesions on her hands and feet caused by trauma or rubbing. Light and electron microscopic studies were performed.
Result: Ultrastructurally, amyloid deposits aggregated under the lamina densa. Keratinocyte protrusions penetrated the dermis through the gap in the lamina densa and enfolded amyloid deposits. Amyloid globules were found in enlarged intercellular spaces of keratinocytes. Desmosomes were sparsely distributed in some areas of the epidermis.
Conclusion: These results indicate that keratinocytes enfold the amyloid globules and take them in the intercellular space of epidermis, and that the breakdown of the lamina densa and widening of the intercellular space between keratinocytes induce skin fragility. Trauma or rubbing of her hands and feet appears to act as the localized precipitating factor of blister formation in bullous amyloidosis.