Corneal dystrophy and perceptive deafness

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 1490

Definition

Corneal dystrophy-perceptive deafness (CDPD) or Harboyan syndrome is a degenerative corneal disorder characterized by the association of congenital hereditary endothelial dystrophy (CHED; see this term) with progressive, postlingual sensorineural hearing loss.

Epidemiology

To date, 24 cases from 11 families of various origins (Asian Indian, South American Indian, Sephardi Jewish, Brazilian Portuguese, Dutch, Gypsy, Moroccan and Dominican) have been reported.

Clinical description

The ocular manifestations in CDPD include diffuse bilateral corneal edema occurring with severe corneal clouding, blurred vision, visual loss and nystagmus. They are apparent at birth or within the neonatal period and are indistinguishable from the ocular findings characterizing autosomal recessive CHED (CHED2). Hearing deficit in CDPD is slowly progressive and is typically identified in patients between 10 and 25 years of age. There are no reported cases with prelingual deafness, however, significant hearing loss in children as young as 4 years old has been detected by audiometry, suggesting that hearing may be affected early in the disease course, even at birth.

Etiology

CDPD is caused by mutations in the SLC4A11 gene located at the CHED2 locus on chromosome 20p13-p12, indicating that CHED2 and CDPD are allelic disorders. A total of 62 different SLC4A11 mutations have been reported in 98 families (92 with CHED2 and six with CDPD).

Diagnostic methods

Diagnosis is based on clinical criteria, detailed ophthalmological assessment and audiometry. Molecular confirmation of the clinical diagnosis is feasible.

Differential diagnosis

A variety of genetic, metabolic, developmental and acquired diseases presenting with clouding of the cornea should be considered in the differential diagnosis (Peters anomaly, sclerocornea, limbal dermoids and congenital glaucoma; see these terms). Audiometry must be performed to differentiate CDPD from CHED2. Autosomal recessive types of CHED (CHED2) and CDPD should be carefully distinguished from the less severe autosomal dominant type, CHED1.

Genetic counseling

More than 50% of the reported CDPD cases have been associated with parental consanguinity and all reported cases have been consistent with autosomal recessive transmission.

Management and treatment

The ocular abnormalities in patients with CDPD may be treated with topical hyperosmolar solutions. However, corneal transplantation (penetrating keratoplasty) represents the definitive treatment. Corneal transplantation results in substantial visual gains and has a relatively good surgical prognosis. Audiometric monitoring should be offered to all patients. Hearing aids may be necessary in adolescence.

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