[Diagnosis of metabolic diseases of the nervous system in children through ultrastructural analysis of non cerebral tissue].

Although biochemical and molecular genetic analysis are the most precise methods for the diagnosis of metabolic diseases, morphological studies remain a very important diagnostic method mainly in countries like Brazil, where clinical laboratories are unable to perform most of the exams required for the diagnosis of these diseases. Moreover, pathologic evaluation is the single diagnostic method for some disorders whose metabolic defect is unknown such as neuronal ceroid-lipofuscinosis, infantile neuroaxonal dystrophy or Lafora disease. We present our experience with ultrastructural analysis in 582 exams of ocular conjunctiva (n = 320), skin (n = 92) or peripheral nerve (n = 170) performed between 1975 and 1996, in 486 children. In 112 cases there were definite ultrastructural changes. In 59 cases, the sole ultrastructural exam allowed the diagnosis. In 29, the changes were less specific, and the final diagnosis was performed by a combination of clinical and pathological analysis. In the remaining 24 cases, a generic diagnosis of mucopolysaccharidosis was done in 8 cases, oligosaccharidosis in 4 cases and GM2 gangliosidosis in 12 cases. Whenever a biochemical test was performed in overseas laboratories, the initial diagnosis was confirmed. These results stress the importance of ultrastructural analysis in non-cerebral tissues for the diagnosis of many metabolic disorders mainly when biochemical tests cannot be performed.