Clinical, biochemical, and histopathological diagnosis of Egyptian paediatric patients with suspected mitochondrial diseases: A hospital based study

Abstract

Background. Mitochondrial respiratory chain (RC) disorders are a growing group of disorders with a large variety of clinical presentations ranging from well-defined clinical syndromes to nonspecific manifestations, such as failure to thrive, exercise intolerance and seizures.

Objective. To describe the clinical, biochemical, and histochemical spectrum of 38 Egyptian patients clinically suspected of having mitochondrial RC disorders.

Methods. A total of 38 patients (female, n=18 (47.4%); male, n=20 (52.6%)) clinically suspected of having mitochondrial diseases had been referred to the Inherited Metabolic Diseases Laboratory at Cairo University Children’s Hospital. Laboratory investigations and analyses included histochemical staining of cytochrome c oxidase and succinate dehydrogenase in muscle biopsies, as well as spectrophotometric assays of RC complexes in muscle homogenates.

Results. Twenty-three patients (60.5%) were diagnosed with different RC enzyme deficiencies. Fifteen patients (65%) had complex I deficiency and all of them also had lactic acidosis (mean (standard deviation)) plasma lactate concentration of 4 (1.65) mmol/L). Two patients (9%) with marked complex IV deficiency both showed COX-negative ragged red fibers (RRFs) on histochemical staining. Combined complex I and complex II deficiency with scattered COX-stain deficiency and RRFs was diagnosed in 2 patients (5.25%), while a further 2 patients (5.26%) had combined (complex I, II+III, complex IV) deficiencies. Isolated complex II deficiency was diagnosed in 2 patients (5.26%) and 15 (39.5%) patients had normal RC enzyme activities.

Conclusion. Biochemical assay of RC complexes is considered the cornerstone for diagnosis of RC complex mitochondrial disorders. These disorders are common among Egyptian paediatric patients.