Sepiapterin Reductase Deficiency (SRD) is a rare inherited neurometabolic disorder caused by variants in the SPR gene, which may lead to developmental delays, psychomotor retardation, and cognitive impairments. Two consanguineous North African and Middle Eastern families are reported with multiple affected individuals presenting with developmental delay, ataxia, hypotonia, fatigue, and ptosis, or parkinsonism and cognitive impairment. Exome sequencing revealed a novel homozygous SPR c.560A>G (p.Glu187Gly) mutation that segregates with disease. According to molecular dynamics analysis, the substitution is predicted to compromise structural integrity, likely affecting ligand binding and catalytic activity. Elevated cerebrospinal fluid sepiapterin and biopterin levels, along with low neurotransmitter levels, were concordant with a genetic diagnosis of SRD and the reclassification of this variant as pathogenic. SRD patients manifest a broad constellation of symptoms, albeit well-managed using low-dose L-dopa/carbidopa. This study highlights the value of genetic testing in expediting early diagnosis and intervention to mitigate the onset of this disorder.
Keywords: ataxia; cognitive delay; developmental delay; neurotransmitter disorders; parkinsonism.