CPT® Code 81460

Whole mitochondrial genome (eg, Leigh syndrome, mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes [MELAS], myoclonic epilepsy with ragged-red fibers [MERFF], neuropathy, ataxia, and retinitis pigmentosa [NARP], Leber hereditary optic neuropathy [LHON]), genomic sequence, must include sequence analysis of entire mitochondrial genome with heteroplasmy detection

Molecular genetic testing for the whole mitochondrial genome is a specialized procedure aimed at identifying mutations within mitochondrial DNA (mtDNA). The mitochondrial genome is composed of 37 essential genes arranged in a double-stranded circular DNA structure, which plays a crucial role in mitochondrial function. Mutations in this genome can manifest as point mutations, deletions, duplications, or complex rearrangements, leading to a variety of mitochondrial disorders. These disorders exhibit a heterogeneous nature and are inherited through the maternal line, meaning they can be passed down from mother to offspring. Mitochondrial disorders predominantly affect tissues with high energy demands, such as muscles and nerves, and can impact multiple systems, particularly in pediatric populations. The clinical presentation of mitochondrial disorders can vary significantly among family members who share the same mutation, highlighting the complexity of these conditions. Unlike nuclear DNA (nDNA), where mutations can be present in zero, one, or two copies of the organelle, mtDNA mutations can exist in varying proportions within the total organelle population, a phenomenon known as heteroplasmy. The severity of symptoms associated with mitochondrial diseases is largely influenced by the degree of heteroplasmy; a higher degree of heteroplasmy typically correlates with more severe clinical manifestations. Common disorders linked to mtDNA mutations include Leigh syndrome, mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); myoclonic epilepsy with ragged-red fibers (MERFF); neuropathy, ataxia, and retinitis pigmentosa (NARP); and Leber hereditary optic neuropathy (LHON). The testing process involves obtaining a blood, skin, or tissue sample to analyze the entire mitochondrial genome for mutations. This is achieved through long-range polymerase chain reaction (LRPCR) followed by next-generation sequencing (NGS) or massively parallel sequencing, which allows for the identification of mutations associated with mitochondrial diseases. This comprehensive testing is often utilized for patients who have previously received negative results from targeted gene mutation analyses for specific mitochondrial disorders or for predictive testing of at-risk family members.