ABSTRACT
Introduction: Mitochondria are organelles that fulfill the energy requirements for cells, which is essential for their survival and function. Mitochondria function is dependent on both mitochondrial (mtDNA) and nuclear genes (Tucker, 2010). SARS2 is a nuclear gene that encodes the mitochondria seryl-tRNA synthetase precursor. It catalyzes the attachment of serine to tRNA and in the biosynthesis of selenocysteinyl-tRNA in the mitochondria. Pathogenic variation in the gene is associated with HUPRA syndrome, which is characterized by hyperuricemia, pulmonary hypertension, renal failure, and metabolic alkalosis (Rivera, 2013). It is important to recognize this autosomal recessive condition as it presents in infancy, can lead to death, and has recurrence implications for carrier couples. Case Description: We present a term neonate male who experienced tachypnea at birth requiring respiratory support;echocardiogram concerning for pulmonary hypertension and right ventricular hypertrophy requiring ionized nitric oxide. During his hospitalization, he developed lactic acidosis (consistently 10–12 mmol/L, reaching 26 mmol/L), seizures, and his newborn screen results flagged as abnormal for severe combined immunodeficiency (SCID) due to low Tcell count. He was transferred to a tertiary medical center due to continued elevated lactate levels. During admission to the tertiary medical center, he was found to have hyperkalemia, elevated BUN/Cr, and elevated lactate levels. Additionally, pre-prandial and postprandial lactate and pyruvate levels were obtained. It was found that hyperlactatemia was persistent and not related to feedings. The patient developed a presumed pulmonary hypertensive crisis at 8 weeks of age, and in the setting of chronic intrinsic renal dysfunction and chronic lactic acidosis, the family elected to transfer him to the home hospital for compassionate extubation where he died. Notable genetics evaluation findings included urine organic acid results showing markedly and persistently elevated levels of fumaric acid and lactic acid concerning for fumarase deficiency or a mitochondrial oxidative phosphorylation disorder and plasma amino acids showing elevated alanine and proline indicative of lactic acidosis. An array CGH showed 2% areas of homozygosity, consistent with known shared parental ancestry. The results of combined mitochondrial genome and Mitochondrial Nuclear Gene Panel was ordered. The results revealed two SARS2 variants: (c.988C>T,p.R330W and c.173T>A, p.L58Q). Both variants were classified as variants of uncertain significance (VUS) based on ACMG-AMP criteria (Richards, 2015) and parental testing to determine phase is ongoing. Discussion: Pathogenic variants in SARS2 lead to dysfunction of seryltRNA synthetase and is associated with HUPRA syndrome. Our patient harbors two variants in SARS2 classified as VUSes but based on clinical presentation the phenotype is consistent with HUPRA syndrome. The condition was first described in 2011 (Belostotsky, 2011) with 6 reported patients from 3 families (Belostotsky, 2011 and Rivera, 2013). Further study into pathogenic mechanism is important as no treatment exists, and the disease leads to death of the infants affected. Although the disease is very rare, it must be considered in infants with who present with symptoms of failure to thrive, hyperuricemia, pulmonary hypertension, renal failure, and metabolic alkalosis.