Paula and Bobby
Parents of Lillie
Chromosome 18p Deletion syndrome
What is Chromosome 18p Deletion syndrome?
Chromosome 18p Deletion syndrome is a rare disease. It is also known as 18p- Syndrome.
More than 150 cases with microscopically visible 18pter deletions have been reported. The del 18pter patients have short stature with variable facial dysmorphism such as round face, large ears, hypertelorism, flat nasal bridge, wide mouth with down-turned corners and single maxillary incisor. Notably 10% of cases have holoprosencephaly for which the putative HPE4 gene has been mapped to 18p11.3 (Overhauser et al., 1995). Gripp et al. (2000) reported 4 missense mutations in the TGIF gene in 268 patients with HPE. An adult female with a visible deletion 18p11.2->pter and partial trisomy for 2p25->pter was reported to have a normal intelligence (Horsley et al., 1998). Other familial microscopically visible 18p deletions have been reported (Tsukahara et al., 2001; Velagaleti et al., 1996; Uchida et al., 1965), some patients with normal or borderline intelligence have been observed.
A submicroscopic deletion was reported by Babovic-Vuksanovic et al., (2004). The patient had moderate mental delay, and developed schizophrenia in his adolescence. He had only mild dysmorphic features (hypertelorism, epicanthic folds, ptosis, round face, wide mouth and large, protruding ears). In studying a larger series of patients with mental retardation Riegel et al. (2001) detected a boy with a trisomy 1q44-qter and a monosomy 18p11.2-pter. He showed profound mental retardation, microcephaly, cleft palate, unilateral postaxial polydactyly, highly arched eyebrows, and small palpebral fissures. His sister may also have been affected. It remained uncertain which symptoms were caused by the del 18pter.
Wester et al., (2006) performed a genotype - phenotype study in 7 patients with a cytogenetically visible 18p deletion, and found that a deletion of the region 18p11.1, in the centromeric region, all had mental retardation, while the ones with a more distal deletion (18p11.21) had a normal or borderline devlopment.
* This information is courtesy of the L M D.
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What gene changes cause Chromosome 18p Deletion syndrome?
The syndrome is inherited in the following inheritance pattern/s:
Microdeletion - Microdeletion inheritance occurs when there is a deletion of several genes on a chromosome. The specific chromosome on which the deletions occur will determine the syndrome they cause.
Multifactorial - If a syndrome is inherited in a multifactorial pattern, it means it is caused by several factors. These factors will be genetic and environmental in nature. Generally, the specific environmental factors are unknown, or yet not proven.
In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation that occurs during the reproductive process.
OMIM Number - 146390 (please check the OMIM page for updated information)
The syndrome can be caused by mutations in the following gene/s location/s:
What are the main symptoms of Chromosome 18p Deletion syndrome?
The typical symptoms of the syndrome are:
Short stature, Hypothyroidism, Cognitive impairment, Gonadal dysgenesis, Global developmental delay, Hypertension, Hypertelorism, High palate, Holoprosencephaly, Abnormality of the antihelix, Abnormality of calvarial morphology, Abnormality of the philtrum, Abnormality of the nose, Abnormal nipple morphology, Aplasia/Hypoplasia affecting the eye, Carious teeth, Wide nasal bridge, Low posterior hairline, Lymphedema, Low-set, posteriorly rotated ears, Misalignment of teeth, Muscular hypotonia, Macrotia, Abnormality of chromosome segregation, Micropenis, Pectus excavatum, Micrognathia, Intellectual disability, Autosomal dominant inheritance, Short neck, Microcephaly, Round face, Radial deviation of finger, Redundant neck skin, Sporadic, Ptosis, Clinodactyly, Cryptorchidism, Decreased testicular size, Downturned corners of mouth, Small for gestational age, Dystonia, Malformation of the heart and great vessels, Cleft palate, Enlarged thorax, Epicanthus, Brachydactyly
How does someone get tested for Chromosome 18p Deletion syndrome?
The initial testing for Chromosome 18p Deletion syndrome can begin with facial genetic analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the type of genetic testing needed. A consultation with a genetic counselor and then a geneticist will follow.
Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.
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