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Erythema nodosum leprosum (ENL). Ultrastructure of the connective tissue response
Abstract:
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.
Insights
Bacterial debris in skin lesions, undetectable by light microscopy, was found using electron microscopy. This debris, linked to mycobacterial antigens, may cause connective tissue damage in ENL.
Area of Science:
- Dermatology
- Microbiology
- Immunology
Background:
- Erythema nodosum leprosum (ENL) involves severe dermal connective tissue damage.
- Previous studies identified immunoglobulin, complement, and inflammatory mediators in these lesions.
Purpose of the Study:
- To investigate the presence and location of bacterial debris in ENL lesions.
- To explore the role of bacterial debris in the pathogenesis of connective tissue damage in ENL.
Main Methods:
- Electron microscopy was used to examine ENL lesions.
- Light microscopy was used as a comparative method.
Main Results:
- Large quantities of degenerating bacterial debris were observed via electron microscopy, but not light microscopy.
- Debris was found within macrophages, extracellularly, and notably bound to damaged collagen and elastic fibers.
- The location of debris coincided with previously identified immune components.
Conclusions:
- Mycobacterial antigen complexation is a significant factor in ENL-related connective tissue damage.
- The precise mechanisms driving variable connective tissue involvement in ENL require further elucidation.