Unilateral, bilateral symmetric or asymmetric isolated hearing loss in patients with heterozygous KITLG variants.

KITLG pathogenic variants have been associated to three distinct clinical presentations with different combinations of hearing loss and/or pigmentation abnormalities. However, its involvement in isolated hearing loss has not been confirmed since its initial description in two families. Besides, KITLG is so far the only gene prevailingly involved in unilateral isolated hearing loss.

Two new cases of mitochondrial myopathy with exercise intolerance, hyperlactatemia and cardiomyopathy, caused by recessive SLC25A4 mutations.

We report the clinical, morphological and molecular features of two patients with autosomal recessive SLC25A4 (ANT1) gene mutations. Furthermore, all previously published cases are reviewed to identify valuable features for future diagnosis. Patients present a common phenotype with exercise intolerance, hyperlactatemia, and hypertrophic cardiomyopathy.

Phenotypic diversity associated with the MT-TV gene m.1644G>A mutation, a matter of quantity.

We describe four patients from three independent families with the m.1644G>A in the MT-TV gene, previously reported without demonstration of its deleterious impact. Very high mutation proportion co-segregated with cytochrome oxidase defect in single muscle fibers and respiratory defect in cybrids as shown by spectrophotometric assays and polarography.