OMIM ID:
Optic Atrophy 2, X-Linked
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Visual symptoms can begin in early childhood (males only) and vision deteriorates slowly. All affected individuals have optic atrophy with acuities ranging from 20/30 to 20/100. ERGs are usually normal whereas VEPs show prolonged latencies. Color vision is variably defective and central scotomas are present.
Systemic Features
Some but not all patients have additional neurological signs including absent ankle jerks, hyperactive knee jerks, extensor plantar reflexes, dysarthria and dysdiadochokinesia. Symptoms are usually minor. Obligatory female carriers do not have optic atrophy or neurologic signs. Mental retardation has been reported in a few patients.
Genetics
Inheritance
This is an X-linked recessive disorder secondary to a mutation in OPA2 (Xp11.4-p11.21). Only males are affected and female carriers are clinically normal.
Pedigree
X-linked recessive, carrier mother
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked recessive, father affected
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.