Erythema nodosum leprosum (ENL). Ultrastructure of the connective tissue response.

In ENL lesions of the type associated with severe damage to the connective tissue of the dermis, large quantities of bacterial debris were demonstrated by electron microscopy, although not by light microscopy. The debris, in an advanced stage of degeneration, was present in the phagosomes of decrepit macrophages, in the extracellular compartment and, in particular, bound to degenerate collagen and elastic where immunoglobulin, complement, and inflammatory mediators had been demonstrated previously. It is suggested that the complexing of mycobacterial antigen is a major factor in the causation of connective tissue damage, as well as other aspects of ENL. The reason why connective tissue involvement is so variable has not been explained.