mitochondrial DNA depletion syndrome type 2

mitochondrial DNA depletion syndrome type 2

An autosomal recessive disorder (OMIM:609560) characterised by childhood onset of muscle weakness and depletion of mtDNA in skeletal muscle. There is wide clinical variability, ranging from onset in infancy with rapid progression and early death due to respiratory failure, to a later onset with a slowly progressive myopathy. 
Molecular pathology
Caused by defects of TK2, which encodes a deoxyribonucleoside kinase required for mitochondrial DNA synthesis.