S-adenosylmethionine and nicotinamide riboside therapy in Arts syndrome: A case report and literature review

Abstract

Phospho-ribosyl-pyrophosphate synthetase 1 (PRPS1) deficiency is secondary to loss of function variants in PRPS1. This enzyme generates phospho-ribosyl-pyrophosphate (PRPP), which is utilized in the synthesis of purines, nicotinamide adenine dinucleotide (NAD), and NAD phosphate (NADP), among other metabolic pathways. Arts syndrome, or severe PRPS1 deficiency, is an X-linked condition characterized by congenital sensorineural hearing loss, optic atrophy, developmental delays, ataxia, hypotonia, and recurrent infections that can cause progressive clinical decline, often resulting in death before 5 years of age. Supplementation of the purine and NAD pathways outside of PRPP-dependent reactions is a logical approach and has been reported in a handful of patients, two with S-adenosylmethionine (SAMe) and one with SAMe and nicotinamide riboside (NR). We present the clinical course of a fourth Arts syndrome patient who was started on therapy and review previously reported patients. All patients had stability or improvement of symptoms, suggesting that SAMe and NR can be a treatment option in Arts syndrome, though further studies are warranted.

Keywords: Arts syndrome; PRPP; PRPS1; S‐adenosylmethionine; nicotinamide riboside; phosphoribosylpyrophosphate.

FIGURE 1

Simplified diagram of the purine synthesis (A) and nicotinamide adenine dinucleotide (NAD) synthesis pathways (B). PRPP (highlighted in yellow) plays a significant role in both pathways. PRPS1 encodes the enzyme PRPP synthetase (highlighted in blue). S‐adenosylmethionine and nicotinamide riboside supplementation is noted in purple.