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HID and KID syndromes are associated with the same connexin 26 mutation
M van Geel1, M A M van Steensel, W Küster
1Department of Dermatology, University Hospital Nijmegen, The Netherlands. m.vangeel@derma.azn.nl
Insights
Keratitis-ichthyosis-deafness (KID) and hystrix-like ichthyosis-deafness (HID) syndromes are genetically identical. Mutation analysis of the connexin 26 (GJB2) gene confirms both conditions share the same molecular basis.
Area of Science:
- Genetics
- Dermatology
- Otolaryngology
Background:
- Keratitis-ichthyosis-deafness (KID) syndrome is a rare genetic disorder characterized by erythrokeratoderma, sensorineural deafness, and an increased risk of squamous cell carcinoma.
- A specific missense mutation in the connexin 26 (GJB2) gene has been identified as a cause of KID syndrome.
- Hystrix-like ichthyosis-deafness (HID) syndrome presents with similar clinical features to KID syndrome, with distinctions historically based on electron microscopy.
Observation:
- This study investigated the genetic relationship between KID and HID syndromes.
- DNA from the first described HID syndrome patient was analyzed for mutations in the connexin 26 (GJB2) gene.
- The researchers utilized polymerase chain reaction and restriction enzyme analysis, a method sensitive to the specific mutation causing KID syndrome.
Findings:
- Mutation analysis revealed that the HID syndrome patient carries the identical connexin 26 (GJB2) mutation previously identified in KID syndrome patients.
- Direct DNA sequencing confirmed the presence of the KID syndrome mutation in the HID syndrome DNA sample.
- These molecular findings demonstrate that HID and KID syndromes are indistinguishable at the genetic level.
Implications:
- The study concludes that KID and HID syndromes are molecularly identical, supporting the clinical suspicion that they represent the same condition.
- Phenotypic variations previously used to distinguish these syndromes may be attributed to sampling artifacts or genetic background effects, such as concurrent mutations in other genes.
- This finding has implications for accurate diagnosis and potential therapeutic strategies targeting the shared molecular pathway in affected individuals.
Background:
Keratitis-ichthyosis-deafness (KID) syndrome is a debilitating ectodermal dysplasia that predisposes patients to develop squamous cell carcinomas in addition to leading to profound sensory deafness and erythrokeratoderma. We recently demonstrated that KID can be caused by a specific missense mutation in connexin 26 (GJB2). Another syndrome, called hystrix-like ichthyosis-deafnesss (HID) syndrome, strongly resembles the KID syndrome. These disorders are distinguished mainly on the basis of electron microscopic findings. We hypothesized that KID and HID syndromes may be genetically related.
Objective:
To demonstrate by mutation analysis that HID and KID syndromes are genetically indistinguishable.
Methods:
DNA was extracted from paraffin-embedded tissue samples of the first HID syndrome patient described in the literature. Since the KID syndrome mutation abolishes an AspI restriction site, we were able to screen the patient's DNA by polymerase chain reaction and subsequent restriction enzyme analysis.
Results:
Restriction analysis of the connexin 26 gene in HID syndrome demonstrated the presence of the KID syndrome mutation that we previously described. This result was confirmed by direct DNA sequencing.
Conclusions:
We show that KID and HID syndromes are identical at the molecular level and confirm the clinical impression that these syndromes are one and the same. That previous clinical reports made a distinction may be a consequence of sampling artefacts; alternatively, genetic background effects such as the presence of concurrent mutations in other skin-expressed genes may modify the phenotype.