Mitochondrial DNA Depletion Testing (Leukocyte)

Use: To diagnose mitochondrial DNA depletion syndrome (MDS). The test is also useful in assessing variants of uncertain significance in nuclear DNA genes that cause MDS. MDS is a clinically heterogeneous group of mitochondrial disorders characterized by a reduction of the mtDNA copy number in affected tissues without mutations or rearrangements in the mtDNA. MDS is phenotypically heterogeneous and can affect a specific organ or a combination of organs, with the main presentations described being either hepatocerebral (i.e. hypotonia, muscle weakness, bulbar weakness), encephalomyopathic (i.e. hypotonia, muscle weakness, psychomotor delay) or neurogastrointestinal (i.e. gastrointestinal dysmotility, peripheral neuropathy). Additional phenotypes include fatal infantile lactic acidosis with methylmalonic aciduria, spastic ataxia (early-onset spastic ataxia-neuropathy syndrome), and Alpers syndrome (see these terms).

Limitations: This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

Methodology: Real-time Quantitative PCR Analysis