Adult patient diagnosed with NADSYN1 associated congenital NAD deficiency and analysis of NAD levels to be published in: European Journal of Medical Genetics

Abstract

IntroductionNicotinamide adenine dinucleotide (NAD) is an essential cosubstrate/coenzyme in multiple cellular redox processes and a substrate in several non-redox reactions. NADSYN1 encodes NAD synthetase 1, an enzyme in the NAD de novo synthesis pathway and the Preiss-Handler pathway, and biallelic pathogenic variants causes NAD deficiency associated with vertebral, cardiac, renal and limb defects. Szot et al. and Kortbawi et al. have reported a total of seven patients with NADSYN1 associated congenital NAD deficiency disorder with the oldest patient being seven years old. Patient dataWe present a male patient age 30 with a height of 130 cm and numerous skeletal malformations including segmentation defects of the spine, rib anomalies and unequal leg length as well as bilateral ptosis, cleft palate and asymmetric dysmorphic facial features. The patient underwent surgery for an aortic stenosis due to a bicuspid valve. No malformations of the kidneys or urinary tract were identified. ResultsTrio exome sequencing revealed a homozygous missense variant in NADSYN1 c.1717G > A (p.Ala573Thr). Both parents were unaffected carriers of the variant. Analysis of NAD levels showed that the patient had a lower NAD pool compared to his unaffected siblings. The NAD pool rose approximately 25% after supplementation with nicotinamide, a NAD precursor for the salvage pathway. ConclusionThe variant was previously reported in four patients and functional analyses by Szot et al. support the pathogenicity of the variant. We report an adult patient with NADSYN1 associated congenital NAD deficiency disorder and expand the phenotypic spectrum. We also present analysis of the NAD levels before and after supplementation with nicotinamide.