ABSTRACT
Since effective therapies appear possible by dietary modification, recognition of a possible metabolic basis in such situations is most important for a future sibling or for a surviving, near-miss case. Since most Mendelian disorders eventually prove to be the result of a deficient or defective product of a specific gene, there is no absolute distinction between inborn errors of metabolism and other genetic disorders. The development of specific tests for direct identification of pathogenic variants is causing rapid changes in our understanding of many inherited metabolic diseases. Prenatal diagnosis is feasible, but decisions about prenatal diagnosis and the termination of affected pregnancies is difficult for some parents in view of the relatively good outcome of treatment for physical health in most cases, although many treated children have a degree of intellectual disability. The classification of the hyperlipidaemias is in a state of flux but is becoming clearer as specific molecular defects underlying the condition are being recognised.
