A novel splice site mutation in the GNPTAB gene in an Iranian patient with mucolipidosis II α/β.

Mucolipidosis type II α/β (ML II α/β) and mucolipidosis type III α/β (ML III α/β) have been shown to be caused by an absence or reduced level of uridine diphosphate (UDP)-N-acetylglucosamine-1-phosphotransferase enzyme (EC 2.7.8.17) activity, respectively. Both disorders are caused by mutations in the GNPTAB gene and are inherited in an autosomal recessive manner. Here we report a 2-year-old female patient being diagnosed as a case of ML II α/β due to coarse face, severe developmental delay, multiple dysostosis, noticeable increase of multiple lysosomal enzymes activity in plasma and normal acid mucopolysaccharides in urine. Mutational analysis of the GNPTAB gene has revealed a novel homozygous mutation in the patient (c.3250-2A>G) with both parents being heterozygote. Transcript analyses showed that this novel splice site mutation leads to exon 17 skipping and a frameshift afterwards (p.P1084_R1112del F1113Vfs*1). Consequently, we confirmed the association of this mutation with ML II α/β. Our finding expands the number of reported cases of this rare metabolic disorder and adds to the GNPTAB mutation database.