Inherited metabolic diseases in the Southern Chinese population: spectrum of diseases and estimated incidence from recurrent mutations

Inherited metabolic diseases (IMDs) are a large group of rare genetic diseases. The spectrum and incidences of IMDs differ among populations, which has been well characterised in Caucasians but much less so in Chinese. In a setting of a University Hospital Metabolic Clinic in Hong Kong, over 100 patients with IMDs have been seen during a period of 13 years (from 1997 to 2010). The data were used to define the spectrum of diseases in the Southern Chinese population. Comparison with other populations revealed a unique spectrum of common IMDs. Furthermore, the incidence of the common IMDs was estimated by using population carrier frequencies of known recurrent mutations. Locally common diseases (their estimated incidence) include (1) glutaric aciduria type 1 (~1/60,000), (2) multiple carboxylase deficiency (~1/60,000), (3) primary carnitine deficiency (~1/60,000), (4) carnitine-acylcarnitine translocase deficiency (~1/60,000), (5) glutaric aciduria type 2 (~1/22,500), (6) citrin deficiency (~1/17,000), (7) tetrahydrobiopterin-deficient hyperphenyla-laninaemia due to 6-pyruvoyl-tetrahydropterin synthase deficiency (~1/60,000), (8) glycogen storage disease type 1 (~1/150,000). In addition, ornithine carbamoyltransferase deficiency and X-linked adrenoleukodystrophy are common X-linked diseases. Findings of the disease spectrum and treatment outcome are summarised here which may be useful for clinical practice. In addition, data will also be useful for policy makers in planning of newborn screening programs and resource allocation.