Chromosome 1p36 Deletion syndrome

What is Chromosome 1p36 Deletion syndrome?

Chromosome 1p36 Deletion was identified in the 1990’s, although cases were recorded as early as the 1980’s. It is a rare chromosomal deletion syndrome.

Severe intellectual disability is one of the main symptoms of the syndrome. Affected individuals also generally have limited to absent speech development and ability. Behavioral issues are also a common feature of this rare disease.

Syndrome Synonyms:
Monosomy 1p36 Syndrome

What gene change causes Chromosome 1p36 Deletion syndrome?

The syndrome is caused due to the loss of a small part of chromosome 1.

Only around 20% of the cases diagnosed are inherited as a result of a parent who carries a balanced translocation. The remainder are de novo or new deletions.

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 which occurs during the reproductive process.

what are the main symptoms of Chromosome 1p36 Deletion syndrome?

Facial and physical characteristics include a small head, large and broad forehead, a pointed chin and flat nasal bridge. Individuals may also experience hearing and vision loss.

Generally individuals experience severe speech delay and many develop limited to zero speech. Low muscle tone is a serious symptom in infancy and may also affect an infant’s ability to feed.

Other health conditions associated with the syndrome include seizures, and heart defects (noncompaction cardiomyopathy being one example).

Possible clinical traits/features:
Intellectual disability, Myopathy, Muscular hypotonia, Leukoencephalopathy, Abnormality of immune system physiology, 11 pairs of ribs, Abnormality of female external genitalia, Abnormal lung lobation, Metatarsus adductus, Microtia, Neurological speech impairment, Neuroblastoma, Myopia, Narrow mouth, Low-set ears, Long philtrum, Low-set, posteriorly rotated ears, Lower limb asymmetry, Wide anterior fontanel, Thickened helices, Submucous cleft hard palate, Renal cyst, Pointed chin, Foot polydactyly, Polymicrogyria, Posteriorly rotated ears, Nystagmus, Sensorineural hearing impairment, Obesity, Ocular albinism, Oppositional defiant disorder, Optic atrophy, Optic disc pallor, Stereotypy, Patent foramen ovale, Pes cavus, Pachygyria, Patent ductus arteriosus, Seizure, Self-mutilation, Rib fusion, Hypoplasia of penis, Short foot, Short toe, Hip dysplasia, Horizontal eyebrow, High palate, Hydrocephalus, Short stature, Hemiplegia/hemiparesis, Hepatic steatosis, Depressed nasal bridge, Gastroesophageal reflux, Gait dis

How does someone get tested for Chromosome 1p36 Deletion syndrome?

The initial testing for Chromosome 1p36 Deletion syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. 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.   

Medical information on Chromosome 1p36 Deletion syndrome

1p36 deletion syndrome is a clinically variable condition characterized by typical craniofacial features including straight eyebrows and a late-closing anterior fontanel. Other features can include intellectual disability, hypotonia, growth abnormalities, congenital heart defects, structural brain abnormalities, seizures, eye/vision problems, hearing loss, skeletal anomalies and renal abnormalities. In some cases, the straight and low-set eyebrows are striking and can be helpful in the diagnosis. Variable cardiac malformations, cardiomyopathy, seizures, ventricular dilatations, sensorineural hearing loss and visual problems have been reported.

Although putative neuroblastoma tumour suppressor gene has been mapped to the 1p36.1-1p36.3 region, in the series of Wu et al. (1999) none of the patients (n=30, ages 2-14 years) developed neuroblastoma. They also showed that the breakpoints were highly variable within 1p36 and that 21 out of 27 de novo deletions were maternally derived (Wu et al. 1999). Slavotinek et al. (1999) reviewed 39 patients with pure 1p36 monosomy (the majority with a microscopically visible deletion) and reported on the association with hypotonia, intellectual disability (usually severe), growth abnormalities (growth retardation, microcephaly, obesity), and facial dysmorphism with a large anterior fontanelle, prominent forehead, deep-set eyes, depressed nasal bridge and midface hypoplasia, ear asymmetry, a pointed chin and orofacial clefting (10- 40% of patients).
Four patients with submicroscopic 1pter deletions were reported by Knight-Jones et al., (2000). All were retarded in terms of growth and development, all were dysmorphic and all had normal chromosomes. Using a multiprobe fluorescence in situ hybridization technique for subtelomeric abnormalities, the 1p deletion was detected. Facially, there were deep-set eyes, a flat midface, a thin lower lip, and cleft lip and palate in two out of the four. Neat horizontal eyebrows appear to be part of the syndrome. All were microcephalic. All had severe intellectual disability, and three were epileptic. Plagiocephaly and delayed closure of the anterior fontanelle were commented on. Congenital heart disease occurred in two, and most had cerebral atrophy.
The very rare Ebstein heart anomaly has been observed in two cases with 1p36.3 deletion (Riegel et al. 1999; Faivre et al. 1998).
Giraudeau et al., (2001) studied 567 patients with intellectual disability and looked for 1p36.3 deletions using a set of highly polymorphic minisatellite probes. Three cases with a deletion were found.
Zenker et al., (2002) reported four further patients. Colmenares et al., (2002) mapped the ski proto-oncogene to 1p36 and showed it was deleted in cases with the 1p36.3 phenotype. Null mice for this gene have a similar phenotype, although interestingly with postaxial polydactyly of the digits on the C57BL/6J strain.
Heilstedt et al., (2003) provide a good clinical and molecular review. Wu et al., (1999) carried out a molecular analysis and revealed different size deletions. Yu et al., (2003) studied 25 cases with DNA microarrays. Breakpoints were variable.
A patient reported by Tan et al., (2005) with features of Cantu syndrome (coarse, hairy, thick ribs, liver disease) turned out to have a 1p36 deletion. In addition, the patient had osteopenia, multiple fractures, high cholesterol and Type 2 diabetes.
A patient described by Neal et al., (2006) had periventricular nodular heterotopia.
Battaglia et al., (2008) evaluated 60 patients. All had straight eyebrows, deep-set eyes, midface hypoplasia, a broad nasal root, long philtrum and pointed chin. They provide an excellent review. Note that infantile spasms are frequent (Bahi-Buisson et al., 2008).
Saito et al., (2011) reported polymicrogyria and infantile spasms. All four patients reported by Oiglane-Shlik et al., (2014) had MRI abnormalities, mostly multiple FLAIR hyperintensities periventricular and in subcortical white matter. Severe behavioural problems, including self-mutilation, might be a clue to the diagnosis (Moog et al., 2005). Disturbed behaviour has been reported varying from temper outbursts to self-injurious behavior. The phenotype might be like Smith-Magenis (Williams et al., 2010, Vieira et al., 2011). The deletion has also been associated with obesity and hyperphagia, as in Prader-Willi syndrome (Haimi et al., 2011). This patient had abnormal liver functions and a severe liver fat storage problem. D'Angelo et al., (2006) stressed that some patients may resemble Prader-Willi syndrome in their behaviour and develop obesity. Obesity is important (D'Angelo et al., 2010).
An OEIS complex phenotype was reported by El-Hattab et al., (2010). Wang and Chen (2004) reported a child with redundant skin in the neck. Further cases were reported by Reish et al., (1995), Giraudeau et al., (1997), Shapira et al., (1997), and Riegel et al., (1999).
Those with a deletion encompassing both proximal and distal segments can be lethal (Nicoulaz et al., 2011). The phenotype was that of a distal deletion but with joint contractures and camptodactyly of digits IV.
Not all patients are severely handicapped (Di Donato et al., 2014). These authors report two brothers (one patent was mosaic) with macrocephaly and near normal intelligence (deletion was 1p36.32).
A female patient with a 4.4Mb deletion in the 1p36 region was reported by Zhang et. al. (2018). Novel clinical characteristics included cutis laxa (wrinkled skin in the abdomen and extensive skin on her back), and hirsutism on the forehead.
A systematic review of electroclinical features of epilepsy associated with 1p36 deletion was presented by Greco et. al. (2018). 34 articles between 1996 and 2016 were included, encompassing 315 patients. Clinical characteristics included seizures in 60.6% of population (no predominant type) with age of onset in infancy (often during the first 6 months of life, but rarely in the neonatal period). Two patterns could be distinguished: a) a few seizures in infancy with no recurrence of seizures after 1 year and b) persistent convulsions, requiring long-term medication. Intractable epilepsy was found in 18.8% of 191 patients. Most frequent brain MRI abnormalities were enlargement of the lateral ventricles (40.6%), cortical atrophy and global cerebral atrophy (33%), white matter abnormalities (11%) and polymicrogyria (2%).

* This information is courtesy of the L M D.
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