PHENYLKETONURIA is an inborn error of metabolism resulting from a deficiency of phenylalanine hydroxylase and characterized by mental retardation. Early diagnosis of phenylketonuria (PKU), a cause of mental retardation, is important because it is treatable by diet. Other features in untreated patients include a 'mousy' odor; light pigmentation; peculiarities of gait, stance, and sitting posture; eczema; and epilepsy (Paine, R. 1957). Kawashima et al. (1988) suggested that cataracts and brain calcification may be frequently overlooked manifestations of classic untreated PKU.
The basic defect in PKU is phenylalanine hydroxylase deficiency. Evidence of heterogeneity in phenylketonuria was presented by Auerbach et al. (1967). The PAH gene located on chromosome 12q24.1 is 90 kb long and codes for a mature mRNA of 2.4 kb. Recurrent mutations had been observed at several sites, producing associations with different haplotypes in different populations. Studies of in vitro expression showed significant correlations between residual PAH activity and severity of the disease phenotype.
This P055-C1 PAH probemix contains probes for all of the 13 coding exons of the PAH gene. In addition 2 probes for the neighbouring genes ASCL1 (upstream PAH) and IGF1 (downstream PAH) are included. For data analysis, 14 reference probes located on other chromosomes are included. This SALSA MLPA kit is not intended to be used for initial diagnosis of PKU. Most defects in the PAH gene are point mutations, the majority of which will not be detected by MLPA. Therefore, it is recommended to use this SALSA MLPA kit in conjunction with sequence analysis.