Role of electron microscopy in the diagnosis of metabolic storage diseases affecting the nervous system of children.

Metabolic storage diseases are among the most challenging diagnostic problems faced by clinicians and pathologists. There is considerable variation in the diagnostic approach to these diseases between different institutions and between different diagnosticians. Much of this variation arises from differences in the availability of and physician confidence in the diagnostic modalities employed to characterize these disorders. Recent advances in the biochemistry and molecular genetics of these diseases have produced some skepticism about the continued relevance of traditional morphologic techniques, including electron microscopy, in their diagnosis. It is the opinion of the authors that this concern is premature and that electron microscopy continues to play a vital role, particularly in the diagnosis of those entities that challenge the classic definitions of lysosomal storage diseases. The authors present a series of cases illustrating different situations where electron microscopy can provide timely, cost-effective, and accurate information in the workup of such diseases.