Zdravstveni dom Vrhnika, Vrhnika, Slovenija
Klinični inštitut za medicinsko genetiko, Univerzitetni klinični center Ljubljana, Ljubljana, Slovenija
M. Žerjav Tanšek
Klinični oddelek za endokrinologijo, diabetes in presnovne bolezni, Pediatrična klinika, Univerzitetni klinični center Ljubljana, Ljubljana, Slovenija
Mitochondrial diseases are a group of disorders caused by impairment of the mitochondrial respiratory chain. They are expressed with very diverse clinical signs and symptoms. Neurological signs and symptoms are most common, although other organ systems can be affected either in isolation or in combinations. All mitochondria contain a 16.6 kb circular double-stranded DNA fragment that encodes 37 genes. The mitochondrial genome is inherited almost exclusively through the maternal line. Each mitochondrion contains many molecules of mitochondrial DNA and each human cell contains hundreds to thousands of mitochondria. If all of the mitochondrial DNA are identical molecules, the condition is described as homoplasmy. A mixed population of normal and mutant mitochondrial DNA is called heteroplasmy and this can apply to a single mitochondrion (some pathological DNA copies mixed with normal ones within one mitochondrion), to a cell (healthy mitochondria mixed with mitochondria harbouring mutated DNA) or to specific tissues (pathological cells mixed with healthy ones). A case report of a baby with a heteroplasmic mutation is presented and mitochondrial inheritance is discussed.
Key words: mitochondrial diseases, mitochondrial inheritance, Leigh syndrome, NARP syndrome.