DNA analysis has also elucidated the molecular genetics and pattern of inheritance involved. Although individual metabolic disorders are rare, collectively, inborn errors of metabolism are not uncommon and paediatricians should be alert to the possibility of such disorders. The presenting symptoms are frequently non-specific and may include lethargy, poor feeding, vomiting, coma, and seizures. Somatic gene therapy may offer hope of a cure for inborn errors of metabolism in the future. The exact incidence in China in different regions still has to be clarified.
Affected neonates appear normal at birth, with dark hair at birth and vomiting is rare.
In infancy and childhood, the fair complexion becomes conspicuous. Head circumference is related to the degree of mental development. These children are mentally retarded with fair complexion but do not have elevated blood phenylalanine levels or urinary ketones. For treatment, we suggest a low-phenylalanine diet for at least for five years and longer, if possible. Gene analysis has revealed differences in the frequency and composition of mutations in northern and southern Chinese patients.