Brief Summary
Teebi type hypertelorism is a rare genetic disease also known as Brachycephalofrontolnasal dysplasia because of the phenotypic symptoms it displays in affected persons.
In 1987, a study conducted by Teebi, identified a four-generation Arab family in which, with some other characteristics indicating craniofrontonasal syndrome, several people displayed striking hypertelorism. A nasal tip that was regular or at most just slightly large and no signs of craniosynostosis or fingernail defects were the findings that distinguished this disease from the previous diagnosis.
History of Disease
Frequency
It affects <1 in 1 000 000 population
Inheritance
Teebi type hypertelorism is inherited in an autosomal dominant pattern.
TEEBI HYPERTELORISM SYNDROME
Pathogenesis
The SPECC1L (Sperm antigen with calponin homology and Coiled-Coil domains 1 Like) found in 22q11.23, the condition is due to heterozygous gain of function variants. The SPECC1L protein is a cytoskeletal protein that affects greater cytoskeletal function by associating with both actin and microtubules. It is involved in cell adhesion, organization of the actin cytoskeleton, stability of microtubules, organization of the spindle, and cytokinesis. Of note, Tessier IV oblique facial cleft causes heterozygous loss of function of SPECC1L.
Pathogenesis
Achondroplasia is caused by a mutation in the FGF3 gene in chromosome 4 at 4p 16.3. This mutation causes a decreased production of fibroblast growth factor receptor 3 which is crucial in the conversion of cartilage into bone which is vital in the proper development of a person. This mutation is inherited in an autosomal dominant manner. More than 80 percent of people with achondroplasia have parents with normal characteristics and are born with achondroplasia due to a recent (de novo) gene modification (mutation).
Symptoms
1
Hypertelorism with upslanting palpebral fissure
2
Prominent forehead
3
Broad and depressed nasal bridge with short nose
4
Thick eyebrows
5
Widow's peak
6
Small broad hands with mild interdigital webbing
7
Shawl scrotum
8
Umbilical and cardiac defects
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Social Concerns
Commonly, bullying can be associated with this disease due to the unusual appearance of the affected individuals.
Treatment
Multidisciplinary medical support with pediatricians, craniofacial, ENT (ear, nose and throat) and abdominal surgeons, cardiologists, and a medical geneticist is required. Neurodevelopmental support and speech therapy may be necessary. Uterine anomalies may cause fertility issues.
Biochemical techniques (research, diagnosis and prognosis)
Prenatal testing is possible for at-risk pregnancies if a SPECC1L mutation has been previously identified in a family member while prognosis is variable but usually favorable, depending on the severity of malformations and associated ID.
Expert Directory
References
[1]OMIM Entry - # 145420 - HYPERTELORISM, TEEBI TYPE; TBHS . (2020). Retrieved 20 November 2020, from https://www.omim.org/entry/145420?search=hypertelorism&highlight=hypertelorism
[2]RESERVED, I. (2020). Orphanet: Hypertelorism, Teebi type. Retrieved 20 November 2020, from https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=1519
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