PNP and Global developmental delay: Previously, a missense PNP gene variant has been reported with no obvious effect on PNP activity and also normal uric acid level was found in an affected child with a mutation in the PNP gene.23 Moreover, developmental delay has been reported in two Iranian patients with PNP.24 However, a recent study showed no neurological defects and developmental delay in an Iranian PNP-deficient patient along with IgA deficiency.25 Therefore, a definite diagnosis of the disease is based on genetic analysis and measuring PNP activity.