THE PATHOLOGISTS APPROACH TO THE DIAGNOSIS OF METABOLIC DISEASE

Many inborn errors of metabolism have tissue changes that suggest or i ndicate a diagnosis on morphologic bases. This emphasizes the involvem ent of the pathologist in the study of tissues obtained by biopsy as p art of the diagnostic workup of cases with clinical evidence suggestin g a metabolic disorder. Some of these diseases involve proteins with e nzymatic activity with a consequent backlog of precursor metabolites. If these metabolites are insoluble or compartmentalized in cells, they accumulate in tissues. The diagnosis in those cases rests on establis hing the nature of the accumulated materials and their topographic dis tribution. In some storage diseases, the abnormal substance can be ide ntified in the affected tissues by histochemistry or ultrastructure. A nother group of inborn disorders of metabolism produce changes in subc ellular organelles such as peroxisomes and mitochondria. A third group is expressed by rather unique tissue changes which strongly suggest t he diagnosis of metabolic disease.