EXTRACEREBRAL BIOPSY IN LYSOSOMAL AND PEROXISOMAL DISORDERS - ULTRASTRUCTURAL FINDINGS

The lysosomal and peroxisomal disorders are characterized by specific storage affecting mainly the central nervous system with involvement o f the peripheral nervous system and visceral organs. Most of these dis orders can now be diagnosed by using biochemical and enzymatical assay s and by molecular biology techniques, without the need for a brain bi opsy used previously. Extraneural tissue biopsies have also been inves tigated at the ultrastructural level. The study of such tissues is sti ll necessary when the enzymatic or biochemical defect remains unknown and when DNA studies are not informative. The choice of tissue is impo rtant. Skin and conjunctival biopsies are less traumatic and are cost- effective diagnostic tools allowing the examination of a great diversi ty of structures. Skeletal muscle and peripheral nerves are more frequ ently used for patients with a late-onset or slower course of disease. Rectal biopsy is helpful when neurons require examination in lysosoma l diseases, whereas liver is more usually investigated than adrenal or testis in peroxisomal diseases. Bone marrow is most useful for Gauche r's disease while lymphocytes may be examined for all lysosomal disord ers as a first diagnostic approach. Chorionic villi still have a diagn ostic role in combination of electron microscopy with DNA studies in e arly pregnancies at-risk for neuronal ceroid lipofuscinosis. Cultured fibroblasts are less informative than other biopsy samples for the mor phological evaluation of lysosomal and peroxisomal disorders.