Electron microscopic features of skin in neurometabolic disorders.

Skin biopsy may contribute to the clinical diagnosis of neurometabolic disorders. It is an easy and much less traumatic procedure than brain, rectal, peripheral nerve and skeletal muscle biopsies. The method is informative and not too time-consuming for an experienced examiner. Differential diagnosis is possible in most storage disorders since the ultrastructure of the storage is virtually typical in lysosomal and in nonlysosomal diseases. The storage has a particular distribution with characteristic ultrastructural patterns in the various cell types. Skin biopsy plays a major diagnostic role when clinical features are atypical for a storage disorder, to discover new phenotypic variants of known enzymatic deficiencies or when the biochemical defect has not yet been determined. It can be used as a screening procedure to orientate the investigations, to suggest specific biochemical assays on cultured fibroblasts or other tissues or body fluids. It can be applied to detect "presymptomatic" patients in affected families. Other disorders of the nervous system should be investigated in the future to ascertain whether skin biopsies could possibly be used for diagnostic purposes. Thorough knowledge of the morphological features of these disorders may also improve the understanding of their pathogenesis, shed some light on the underlying basic defects and control the results of therapy.