Epidermolysis bullosa

Introduction

Epidermolysis bullosa comprises a group of genetically determined disorders which usually results from minor mechanical trauma, but may arise spontaneously. A comprehensive classification of this complex and heterogeneous group has been based on clinical presentation, genetic pattern of inheritance and electron microscopic features which had been proposed in 1991 by the Subcommittee of National EB Registry (USA).[1] These are simple with intraepidermal split, Junctional with intralaminallucida split and dystrophic with sub lamina densa split, with about 25 sub types.

All specimens should preferably be subjected to two types of investigations viz electron microscopy (EM) and immunofluorescence mapping (IM). The EM has now demonstrated that the level of cleavage in the skin is different in the major group of syndromes and also there are a number of ultrastructural abnormalities. The latter procedure consists of exposing cryostat section to specific antisera against type IV collagen, laminin, or bullous pemphigoid antigen.[2]

Case Report

A 33-year-old serving soldier was admitted with history of recurrent blisters over both shins since the age of 20 years recurring mostly in summer months. There was history of consanguinous marriage but pedigree analysis was normal.

On examination he was found to have a few vesicles over both shins along with old atrophic and few hypertrophic scars [Figure - 1]. On induction of friction by eraser he developed vesicles with positive bulla spread sign. Nikolsky′s sign was negative. Examination of nails, teeth, hair and mucosa was normal. General and systemic examination were essentially normal.

Clinically he was diagnosed as a case of I dystrophic epidermolysis bullosa (DEB) of pretibial variety. Light microscopic histopathology of an induced bulla showed functional bulla with few neutrophils, eosinophils and lymphocytes with no acantholytic cells and doubtful sub epidermal split at places. Electron microscopy however showed a subepidermal (sub lamina densa) split.

Routine haematological and biochemical parameters including blood sugar were normal.

Discussion

EB is a genodermatosis, the pattern of inheritance being either autosomal dominant (AD) or autosomal recessive (AR). Our case had history of consanguinous marriage but pedigree analysis was normal.

Clinically the lesions were limited to pretibial region with both atrophic and hypertrophic scars fitting in to the subtype-pretibial DEB though the pattern of inheritance was AR instead of AD.

Histopathologically light microscopy showed a mixed picture of juctional bulla, at places the PAS positive basement membrane was alongwith the detached epidermis indicating the bullae to be sub-epidermal. This confusion was sloved by EM which confirmed it to be a sub epidermal (sub lamina densa) split, thereby emphasizing the necessity of EM in all such cases, in addition to immunoflurescence mapping, to reach a definitive diagnosis.

Another interesting feature was the localisation of the lesion to pretibial region. Being a serving soldier mechanical trauma is expected due to ankle boots and high woollen socks, yet sparing of the feet and soles can′t be explained, which could be due to the disease predilection per se.