Abstract
Abstract
Inherited metabolic diseases are caused by deficiencies of enzymes or transport proteins. Most are diagnosed by biochemical analysis of blood or urine, or enzyme assays, but some require genetic tests. They are classified according to the organelle or pathway involved. For lysosomal disorders, the characteristic dermatological findings are ‘coarse’ facial features (as in the mucopolysaccharidoses) and angiokeratomas (as in Fabry disease). Many congenital defects of glycosylation have dermatological features, such as fat pads and inverted nipples, ichthyosis or cutis laxa. This chapter also covers disorders of the mitochondria, amino acid and biotin metabolism and zinc and copper transport, along with familial tumoral calcinosis. Porphyrias and lipid disorders causing xanthomas, ichthyosis or lipodystrophy are considered elsewhere. Enzyme replacement therapy is available for several lysosomal disorders, including Fabry disease. Other metabolic diseases often respond to dietary treatment, drugs or pharmacological doses of nutrients but for some conditions there is no satisfactory treatment.