Abstract
The Inborn Errors of Metabolism and Neurology Services of the King Faisal Specialist Hospital and Research Centre (KFSH&RC) and Armed Forces Hospital have received more than 1,500 patients suspected of having an organic acid disorder (OAD) during a period of four years. Of these, 307 patients, approximately 20%, had a clearly identifiable disorder. Identified OAD's constituted one-quarter of all patients diagnosed as having various types of inborn errors of metabolism during this period, in these clinical services. Prolonged follow-up was available in the majority of cases, allowing detailed clinical, neuroradiologic and neurophysiologic descriptions. Fifty patients (16%) had rare disorders by standards in the West. Approximately 25% were 'neurologic organic acidurias'. This is a new term we are introducing for OAD's manifesting primarily with neurologic signs, but without appreciable acidosis, hypoglycemia or hyperammonemia. In this special issue, we present the KFSH&RC experience with the rare disorders as individual articles. We estimate the frequency of OAD's in Saudi Arabia as 1/740 births. The increased frequency of OAD's in Saudi Arabia is probably due to increased consanguinity, since most OAD's occurred in excess in certain tribes; and due to increased surveillance and testing by our group. Saudi Arabia provides a unique opportunity for research in this area of pediatrics.