Mitochondrial DNA depletion syndrome 13. A case report

Abstract

The etiology of cerebral palsy in children with intrauterine hypotrophy at birth and developmental delay is often explained by chronic intrauterine hypoxia. However, children with muscle hypotonia and developmental delay require genetic examination. The aim of this study is to report a case of mitochondrial disease caused by FBXL4 gene mutations and to identify main diagnostic criteria for mitochondrial DNA (mtDNA) depletion syndromes (MDS) in early childhood. Mitochondrial DNA depletion syndrome-13 is associated with FBXL4 gene mutations located in the 6q16.1–q16.27 locus. This disorder was first described in 2013 by P.E. Bonnen and X. Gai independently. MDS are a clinically and genetically heterogeneous group of diseases inherited by an autosomal recessive type and caused by mutations in genes that support the biogenesis and integrity of mtDNA. Encephalomyopathic mtDNA depletion syndrome-13 (MTDPS13) (OMIM: 615471) is an exceedingly rare autosomal recessive disease caused by biallelic mutations in the FBXL4 gene (MIM: 605654) with an estimated prevalence of 1 case per 100,000– 400,000 newborns. The disease onset is usually observed in the neonatal period; 75 % of patients develop symptoms by the age of 3 months. In the majority of cases, mtDNA depletion syndrome-13 manifests itself in the early neonatal period; however, in some patients, the disease onset was registered by the age of 24 months. The disease is characterized by encephalopathy, hypotension, lactic acidosis, severe developmental delay, and changes in the area of basal ganglia revealed by magnetic resonance imaging of the brain. FBXL4-related encephalomyopathy is a multisystem disease primarily affecting the central nervous system, heart, and liver. It is characterized by different clinical manifestations such as lactic acidosis, developmental delay, generalized hypotension, nutritional disorders, and growth retardation. Some patients demonstrate specific facial features, including prominent forehead, sinus-shaped folds, thick eyebrows, long eyelashes, epicanthus, short eye slits, hypertelorism, wide and depressed nose bridge, long and smooth labial groove, thin upper lip, and low-set ears. The disease prognosis is extremely poor; most children die before the age of 4 years. Approximately half of the patients suffer from microcephaly and hyperammonemia. The outcome varies; death was reported in 30 % of cases. Mean time to death was 3 years (median – 2 years). The diagnosis is crucial for medical and genetic counseling and possible prenatal diagnosis.