Genetic Causes and Genetic Diagnostic Testing of Inherited Optic Atrophies

Hereditary optic atrophies are a heterogeneous group of rare degenerative disease affecting the retinal ganglion cells and their axons which form the optic nerve. With an estimated prevalence of 1:10000 to 1:20000, hereditary optic atrophies in their entirety affect about 4000 to 8000 people in Germany. The most common forms are Leber's hereditary optic atrophy (LHON) and autosomal dominant optic atrophy (ADOA). Besides the common forms of isolated optic atrophies which exclusively affect the visual system, there are a variety of conditions in which the optic atrophy is part of a syndromic disease with additional symptoms that are mostly neurosensory, neurological or neuromuscular. The mode of inheritance is heterogeneous with LHON showing maternal inheritance and an autosomal dominant inheritance in families with ADOA. There are rarer cases of optic atrophy following an autosomal recessive or X-linked recessive mode of inheritance. The penetrance is incomplete. Moreover, in LHON, there are many more males than females who develop the disease. The genetic causes of hereditary optic atrophies are complex in terms of the diversity of the involved genes. However, most of these causes are already known. Therefore, molecular genetic diagnostic testing yields a meaningful result in the majority of tested subjects and enables confirmation of the suspected clinical diagnosis, reliable counseling of the families with respect to the genetic risk, and - in subjects with genetically confirmed LHON - initiation of therapeutic intervention. This article provides an overview of current knowledge of the genetic causes of hereditary optic neuropathies, and the options and modalities of molecular genetic diagnostic testing, including practical guidelines.