Harboyan syndrome
What is Harboyan syndrome?
Harboyan syndrome, also known as corneal dystrophy-perceptive deafness (CDPD), is an inherited, degenerative disorder characterized by congenital hereditary endothelial dystrophy, or corneal clouding resulting in a ground-glass appearance, with gradual hearing loss. CDPD includes symptoms such as diffused bilateral corneal edema with severe corneal clouding, blurred vision, vision loss, and nystagmus or uncontrolled eye movements.
Synonyms
- Corneal dystrophy with progressive deafness
Harboyan syndrome, also known as corneal dystrophy-perceptive deafness (CDPD), is an inherited, degenerative disorder characterized by congenital hereditary endothelial dystrophy, or corneal clouding resulting in a ground-glass appearance, with gradual hearing loss. CDPD includes symptoms such as diffused bilateral corneal edema with severe corneal clouding, blurred vision, vision loss, and nystagmus or uncontrolled eye movements.
Harboyan syndrome is an extremely rare disorder. A total of 24 cases of Harboyan syndrome from 11 families of various origins (Asian Indian, South American Indian, Sephardi Jewish, Brazilian Portuguese, Dutch, Gypsy, Moroccan, and Dominican) have been reported.
| Name | Abbreviation |
|---|---|
| Corneal dystrophy with progressive deafness | CDPD |
Harboyan syndrome is caused by a mutation in the SLC4A11 gene, located at the congenital endothelial corneal dystrophy (CHED2) locus on chromosome 20. As there are 23 chromosome pairs in the normal genome, one inherits 2 copies of each gene. Each of these genes may display distinct variations known as alleles. This means that Harboyan syndrome and CHED2 are allelic disorders, two diseases caused by mutations on the same gene. Over half of the cases reported have been associated with parental consanguinity, meaning that the parents of the affected individual share blood relations, suggesting that CDPD is likely an autosomal recessive disorder.
The most noticeable symptom of Harboyan syndrome is a “ground glass cornea” appearance known as bilateral corneal edema. Corneal clouding is usually observed very early on, either at birth or within the neonatal period. Physicians should also look for nystagmus, or uncontrolled eye movements, which is another symptom of CDPD. However, these ocular findings also match the symptoms for CHED2, thus audiometry must be performed to test for hearing loss in order to distinguish CDPD from CHED2. Although hearing loss is not reported at birth, affected individual’s hearing slowly deteriorates between the ages of 10 and 25.
All cases of Harboyan syndrome in the past have been associated with the SLC411 gene. A diagnosis can be made upon a detailed ophthalmological (eye) assessment. With Harboyan syndrome and CHED2, there is evident clouding of the entire cornea and central corneal thickness is also increased.
Endothelial dystrophy, or corneal clouding, can be confirmed by removing a sample of the cornea and identifying severely degenerated corneal endothelial cells and abnormal thickening of Descernet’s membrane. Audiometry can also measure hearing acuity for variations of sound intensity, pitch, and tonal purity. Studies with affected individuals ages 4-19 have shown that the degree of hearing loss ranges from -30 dB to -60 dB.
Hypertonic sodium chloride solutions can help some people by producing temporary corneal dehydration. The most ideal treatment to restore vision and avoid amblyopia, or the “lazy eye”, is corneal transplantation. Individuals should expect a gradual recovery of vision following the surgery over the course of 6 to 12 months.
Harboyan syndrome does not reduce the life expectancy of an individual. An affected individual’s vision can be greatly improved with a corneal transplant.
Corneal dystrophy - perceptive deafness. Orphanet. http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=1490.
Abramowicz M., Desir J. Congenital hereditary endothelial dystrophy with progressive sensorineural deafness (Harboyan syndrome). NCBI. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2576053/.
Harboyan Syndrome. The University of Arizona. http://disorders.eyes.arizona.edu/disorders/harboyan-syndrome
Corneal Dystrophy, Congenital Endothelial 2. The University of Arizona. http://disorders.eyes.arizona.edu/disorders/corneal-dystrophy-congenital-endothelial-2
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CoRDS, or the Coordination of Rare Diseases at Sanford, is based at Sanford Research in Sioux Falls, South Dakota. It provides researchers with a centralized, international patient registry for all rare diseases. This program allows patients and researchers to connect as easily as possible to help advance treatments and cures for rare diseases. The CoRDS team works with patient advocacy groups, individuals and researchers to help in the advancement of research in over 7,000 rare diseases. The registry is free for patients to enroll and researchers to access.
Enrolling is easy.
- Complete the screening form.
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- Answer the permission and data sharing questions.
After these steps, the enrollment process is complete. All other questions are voluntary. However, these questions are important to patients and their families to create awareness as well as to researchers to study rare diseases. This is why we ask our participants to update their information annually or anytime changes to their information occur.
Researchers can contact CoRDS to determine if the registry contains participants with the rare disease they are researching. If the researcher determines there is a sufficient number of participants or data on the rare disease of interest within the registry, the researcher can apply for access. Upon approval from the CoRDS Scientific Advisory Board, CoRDS staff will reach out to participants on behalf of the researcher. It is then up to the participant to determine if they would like to join the study.
Visit sanfordresearch.org/CoRDS to enroll.
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