Norrie Disease - Causes

Causes

Norrie disease is a genetic disorder caused by mutations in the NDP gene, located on Xp11.4 (GeneID: 4693). It is inherited in an X-linked recessive way from usually one of your parents. This means that almost only males are affected. Sons of affected men will not have the mutation, while all of their daughters will be genetic carriers of the mutation. They also usually show no clinical symptoms, but will inherit the mutation to 50% of their offspring. Daughters receiving the mutated gene will also be, like their mother, asymptomatic carriers, but 50% of their sons will express clinical symptoms.

Females are very unlikely to express clinical signs. One possible scenario leading to this (unlikely) case would be if both of their copies of the NDP gene bear mutations, which could be the case in consanguineous families or due to a spontaneous somatic mutation. Another explanation for affected females could be skewed X-Chromosome inactivation.

However, throughout history, there have been a few rare cases where females have shown symptoms associated with Norrie disease such as retinal abnormalities and mild hearing loss.