Shahmeer Hamid

Introduction

Norrie disease is a rare, severe inherited neurodevelopmental disorder primarily affecting the eye. It was first described by the Danish ophthalmologist Gordon Norrie in 1927, and later, Dr. Mette Warburg established its X-linked recessive inheritance pattern in 1961. The condition is caused by mutations in the NDP gene located on chromosome Xp11.3, which encodes the protein norrin. Norrin is a secreted protein that acts as a ligand for the Wnt/β-catenin signalling pathway (binding to the Frizzled-4 receptor), playing a critical role in the vascular development of the retina and the stria vascularis of the cochlea (1).

Norrie disease is characterised by congenital blindness due to retinal dysplasia and is frequently associated with progressive sensorineural hearing loss and varying degrees of cognitive impairment. It predominantly affects males, while female carriers are usually asymptomatic or present with mild retinal findings (2).

Clinical Stages

Neonatal/Infancy (Ocular Onset)

○​ Leukocoria: The hallmark presentation at birth or within the first few months is a greyish-yellow pupillary reflex (“cat’s eye reflex”).

○​ Pseudoglioma: Examination reveals bilateral dysplastic retinal masses behind the lens, resulting from the failure of retinal vascular development.

○​ Retinal Detachment: Total or partial haemorrhagic retinal detachment is typically present at birth.

Childhood (Ocular Progression)

○​ Phthisis Bulbi: Over time, the eyes undergo atrophy and shrinkage (phthisis), leading to sunken globes.

○​ Anterior Segment Changes: Patients may develop cataracts, corneal opacification (band keratopathy), and synechiae (adhesions between the iris and lens).

Adolescence/Adulthood (Auditory and Systemic Onset)

○ Hearing Loss: Progressive sensorineural hearing loss typically begins in the second decade (median age 12 years). It is initially asymmetrical and high-frequency, eventually leading to profound deafness (3).

○​ Cognitive & Behavioural: Approximately 30–50% of patients exhibit developmental delay or intellectual disability. Behavioural issues, including psychosis-like features, may occur.

○​ Vascular: Peripheral vascular disease, manifesting as venostasis or ulcers in the lower extremities, has been reported in adult patients.

Investigations

Diagnosis is established through clinical findings and confirmed by molecular testing:

Genetic Testing

Identification of hemizygous pathogenic variants in the NDP gene confirms the diagnosis.

B-Scan Ultrasonography

Essential for differentiating Norrie disease from retinoblastoma. In Norrie disease, the retrolental mass typically lacks acoustic shadowing from calcification, whereas retinoblastoma would show high reflectivity and acoustic shadowing from calcium.

MRI Brain

May define the extent of ocular dysplasia and rule out intracranial abnormalities.

Audiology

Regular audiometric assessments are crucial to detect early sensorineural hearing loss (4).

Differential Diagnosis

Conditions to differentiate from Norrie disease include:

Retinoblastoma: A life-threatening malignancy; differentiating features include calcification on ultrasound (common in retinoblastoma, absent in Norrie).

Familial Exudative Vitreoretinopathy (FEVR): Genetically related (also involving Wnt pathway genes) but typically presents with less severe retinal findings and lacks systemic associations.

Retinopathy of Prematurity (ROP): distinguished by a history of premature birth and oxygen therapy.

Persistent Foetal Vasculature (PFV): Usually unilateral and non-hereditary.

Coats Disease: Typically unilateral retinal telangiectasia with exudation (5).

Management

There is currently no cure for Norrie disease, and management is supportive and multidisciplinary.

Ocular

Visual prognosis is poor. Surgery (vitrectomy) is rarely effective for restoring vision but may be indicated to preserve the globe or treat complications like neovascular glaucoma. Enucleation may be necessary if the eye becomes painful.

Auditory

Early provision of hearing aids is vital. Cochlear implants have shown significant benefit for patients with profound deafness, improving quality of life and communication.

Systemic

Developmental support and behavioural therapy are indicated for cognitive impairments. Genetic counselling is essential for affected families (2).

Prognosis

The visual prognosis is universally poor, with most patients having no light perception (NLP) from infancy. The auditory prognosis involves progressive deterioration, often resulting in profound deafness by mid-adulthood, creating a dual sensory impairment (deaf-blindness). Life expectancy is generally normal, though quality of life is heavily influenced by the degree of cognitive impairment and the management of sensory deficits (6).

Conclusion

Norrie disease is a rare, X-linked recessive disorder defined by congenital blindness, progressive hearing loss, and potential cognitive deficits. It results from mutations in the NDP gene, disrupting crucial Wnt signalling pathways necessary for neurovascular development. While vision is rarely preservable, early diagnosis allows for important genetic counselling and the timely management of hearing loss, which is central to maximising the patient’s functional independence.

References

1. Berger W, Meindl A, van de Pol TJ, et al. Isolation of a candidate gene for Norrie disease by positional cloning. Nat Genet. 1992;1(3):199-203. doi:10.1038/ng0692-199

2. Smith SE, Mullen TE, Graham D, Sims KB, Rehm HL. Norrie disease: extraocular clinical manifestations in 56 patients. Am J Med Genet A. 2012;158A(8):1909-1917. doi:10.1002/ajmg.a.35469

3. Halpin C, Owen G, Gutiérrez-Espeleta GA, Sims K, Rehm HL. Audiologic features of Norrie disease. Ann Otol Rhinol Laryngol. 2005;114(7):533-538. doi:10.1177/000348940511400707

4. Warburg M. Norrie’s disease. A congenital progressive oculo-acoustico-cerebral degeneration. Acta Ophthalmol (Copenh). 1966;1-47.

5. Scruggs BA, Reding MQ, Schimmenti LA. NDP-Related Retinopathies. 1999 Jul 30 [Updated 2023 Mar 23]. In: Adam MP, Bick S, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1331/

6. Roche O. Norrie disease. Orphanet encyclopedia, July 2005. Available at: https://www.orpha.net.