Abstract

Introduction: Polynucleotide phosphorylase is involved in RNA processing in mitochondria. Biallelic variants in PNPT1 cause mitochondrial RNA import protein deficiency and heterogeneous clinical manifestations.

Case Report: The patiest was the first child of remote consanguineous parents, born at 35 weeks by caesarean section due to fetal growth restriction. Apgar index was 9/10/10. Birth weight, length and head circumference were at 3rd, <3rd and 10th percentiles, respectively. In the first hours of life, respiratory distress, hypoglycaemia and seizures ensued. She started invasive mechanic ventilation, phenobarbital and was transferred to ICU. Physical examination showed minor facial dysmorphisms, brief eye-opening, hypotonia and hyporeflexia. Electroencephalogram showed immature pattern and multifocal paroxysmal activity. MRI at D8 of life showed severe reduced brain volume. Normal aminoacid screen was also observed. Expanded newborn screening was negative. Mitochondrial organic aciduria was seen. WES showed a homozygotic likely pathogenic variant in the PNPT1 gene. MRI at 6-months showed brain atrophy, thin corpus callosum, reduced brainstem volume. Bilateral and symmetrical lesions in globi pallidi, compatible with Leigh síndrome were observed. Currently, at 14 months, no neurodevelopment progress, dystonia, visual deficit, sensorineural deafness, hypertrophic cardiomyopathy and microcephaly are observed.

Conclusion: The early and severe Leigh-like presentation of our patient expands the phenotype spectrum of this disease. As far as we know, this is the first reported case of PNPT1 mutation with onset in the perinatal period. Moreover, hypertrophic cardiomyopathy has not yet been described in association with mutation of the PNPT1 gene. WES was the key for early diagnosis in this patient. It should be done in all children with severe clinical presentation of unknown origin.