During the research, 3 types of this disease were identified, and also 4 forms-quite rare.
I type of disease is characterized by congenital complete deafness, as well as a balance disorder. Often, these children begin to walk only at the age of 1.5 years. Deterioration of vision usually begins with 10 years, and the final development of the state of night blindness begins with 20 years. Children with this type of disease can develop progressive deterioration of peripheral vision.
With type II disease , moderate or congenital deafness is observed. Often, in this case, deterioration with partial deafness no longer occurs. Pigment retinitis begins to develop around the end of the adolescent period or after 20 years. The development of night blindness usually begins in the 29-31 year. Disturbances in visual acuity in case of type II pathology basically progress slightly more slowly than in type I.
III type of the disease is characterized by a progressive loss of hearing, usually beginning during puberty, and also by the gradual appearance in the same period (slightly later than the hearing loss) of retinitis pigmentosa, which can become a factor in the development of progressive blindness.
Manifestations of the fourth type of pathology mainly occur in males. In this case, there are also progressive disorders and loss of hearing and vision. This form is very rare and usually has an X-chromosome nature.