Recessive mutations in NDUFA2 cause mitochondrial leukoencephalopathy.

Deficiencies of mitochondrial respiratory chain complex I frequently result in leukoencephalopathy in young patients, and different mutations in the genes encoding its subunits are still being uncovered. We report 2 patients with cystic leukoencephalopathy and complex I deficiency with recessive mutations in NDUFA2, an accessory subunit of complex I. The first patient was initially diagnosed with a primary systemic carnitine deficiency associated with a homozygous variant in SLC22A5, but also exhibited developmental regression and cystic leukoencephalopathy, and an additional diagnosis of complex I deficiency was suspected. Biochemical analysis confirmed a complex I deficiency, and whole-exome sequencing revealed a homozygous mutation in NDUFA2 (c.134A>C, p.Lys45Thr). Review of a biorepository of patients with unsolved genetic leukoencephalopathies who underwent whole-exome or genome sequencing allowed us to identify a second patient with compound heterozygous mutations in NDUFA2 (c.134A>C, p.Lys45Thr; c.225del, p.Asn76Metfs*4). Only 1 other patient with mutations in NDUFA2 and a different phenotype (Leigh syndrome) has previously been reported. This is the first report of cystic leukoencephalopathy caused by mutations in NDUFA2.

LPIN1 deficiency with severe recurrent rhabdomyolysis and persistent elevation of creatine kinase levels due to chromosome 2 maternal isodisomy.

Fatty acid oxidation disorders and lipin-1 deficiency are the commonest genetic causes of rhabdomyolysis in children. We describe a lipin-1-deficient boy with recurrent, severe rhabdomyolytic episodes from the age of 4 years. Analysis of the LPIN1 gene that encodes lipin-1 revealed a novel homozygous frameshift mutation in exon 9, c.1381delC (p.Leu461SerfsX47), and complete uniparental isodisomy of maternal chromosome 2. This mutation is predicted to cause complete lipin-1 deficiency. The patient had six rhabdomyolytic crises, with creatine kinase (CK) levels up to 300,000 U/L (normal, 30 to 200). Plasma CK remained elevated between crises. A treatment protocol was instituted, with early aggressive monitoring, hydration, electrolyte replacement and high caloric, high carbohydrate intake. The patient received dexamethasone during two crises, which was well-tolerated and in these episodes, peak CK values were lower than in preceding episodes. Studies of anti-inflammatory therapy may be indicated in lipin-1 deficiency.