OMIM ID:
Cataracts, Ataxia, Short Stature, and Mental Retardation
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Cataracts are present in both sexes but the opacification is more extensive in males and only partial in females. The cataracts are congenital in males but apparently develop later in females who complain of blurred vision from early childhood or during teenage years. The lenses in females have punctate and pulverulent opacities as well as posterior subcapsular sclerosis. Vision has been estimated as hand motion from early childhood in boys and about 20/40 in females in the first two decades of life.
Systemic Features
Males have mild to moderate mental retardation, muscle hypotonia and weakness with postural tremor. Their standing position is broad-based and they are unable to sit or stand otherwise without some support. They are usually unable to walk unassisted. Speech is dysarthric and its development is delayed. Females are neurologically normal.
Genetics
Inheritance
A locus containing the disease allele at Xpter-q13.1 cosegregates with the cataract phenotype in both sexes. The gene mutation has not been identified. This can be called an X-linked recessive disorder with partial expression in heterozygous females.
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.