A clinical case of a hypertrophic phenotype of cardiomyopathy in a child with a combined deficiency of oxidative phosphorylation type 3 associated with a mutation of the TSFM gene

Combined oxidative phosphorylation deficiency type 3 is a rare mitochondrial disease caused by pathogenic variants in the mitochondrial elongation factor (TSFM) gene. The function of this protein is highly active in cardiomyocytes and neurons, so the manifestations of the disease are neurological and cardiac symptoms. Heart damage occurs predominantly as concentric hypertrophy of the left ventricle. From the nervous system, the most observed are muscle hypotonia and choreo-like dyskinesis. In this article, we present a clinical case of combined type 3 oxidative phosphorylation deficiency, which was characterized by the early onset of neurological symptoms and subsequent myocardial hypertrophy at the age of 10 years. This is the second case of the C919T:p.Gln307Ter mutation in the TSFM gene in the literature we studied. Today, the disease is characterized by high mortality at onset from birth and stabilization of the clinical course with asymptomatic or late onset of the disease. The small number of cases of combined oxidative phosphorylation type 3 deficiency leaves many clinical questions, and the description of each genetically confirmed case is extremely important.