Mitochondrial Disorders (MD) include a heterogeneous group of inherited disorders due to molecular
defects mainly affecting the mitochondrial oxidative phosphorylation system. Because the respiratory chain is
under control of two different genomes (nuclear DNA-nDNA and mitochondrial DNA-mtDNA), mitochondrial
genetics is quite complex and may justify the extreme clinical heterogeneity of these diseases. Clinically, MD
usually involve multiple tissues, mainly affecting organs with high energy request as central nervous system
and skeletal muscle. They may present at any age, with different onsets, clinical presentation and progression
from an isolated involvement of vision or hearing to a multisystemic degenerative disorders with stroke-like
episodes, peripheral neuropathy, ophthalmoparesis, seizures, cardiopathy, hepatopathy, endocrinopathies,
etc. Over the last 50 years, it became evident that MD represent an important part of the general medicine.
The complexity of clinical and genetic spectrum of those disorders is still increasing. The aim of this review is
to walk through mitochondrial genetics, highlighting novel clinical entities.