Norrie disease.
Incidence
It is a rare, X-linked form of congenital blindness. ND is transmitted as a fully penetrant, X-linked trait. Heterozygous females typically do not show any signs of the disease, however, in a few instances they may be symptomatic.
Clinical Characteristics
Norrie disease is a rare, X-linked form of congenital blindness characterized by severe, bilateral abnormalities of eye development. These abnormalities include the presence of a tumorlike retrolental mass, termed "pseudoglioma," which is composed of layered and highly vascularized collagenous tissue, probably resulting from an early arrest of embryonic retinal development. Approximately one-third of patients with Norrie disease have sensorineural hearing loss, which usually appears in early or middle childhood and maintains a progressive course to complete deafness. Norrie disease (ND) is a rare inherited form of congenital blindness. In most patients the phenotype is evident at birth and is characterized by severe, bilateral abnormalities of eye development. These abnormalities include the presence of a tumorlike retrolental mass, retinal detachment, iris atrophy and synechiae, corneal and vitreous opacities, and glaucoma. The detached retina often can be detected as leukokoria (white pupil reflex). Most patients are blind at birth or by the end of the second month of life, but some preserve light perception in the first few years. Phthisis bulbi (severe shrunken atrophy of the optic globe) usually develops by the end of the first decade. In some patients eye abnormalities are associated with defects involving other organs and tissues. Approximately one-third of ND patients have sensorineural hearing loss, which usually appears in early or middle childhood and follows a progressive course to complete deafness. Mental retardation and psychotic behavior are also common findings in ND patients. Has been pointed out that blindness by itself can cause developmental stasis or regression, particularly when the developmental climate is suboptimal. There is, however, no doubt about the causal relationship between ND and mental retardation, given the number of patients with mental retardation described who had received adequate care and in whom a point mutation in the ND gene was found. Expressivity of the phenotype is variable, even within the same family, and particularly with respect to deafness and mental retardation. Dysmorphic features, including a typical "Norrie facies," microcephaly, cryptorchidism, growth retardation, and limb anomalies have been reported in some patients with ND. These patients had large deletions probably involving other flanking genes in addition to the Norrie gene and resulting in a contiguous gene syndrome. There is no pharmacologic treatment available for ND. Symptomatic therapy includes enucleation and replacement with an artificial eye and the use of hearing aids.
Precipitants
no
Provocation Tests
no
Diagnostic Procedures
DB-F, DB-W. In several patients a point mutation in the ND gene was found.