ASXL2

On this page, you will find information about a genetic change that was identified in a UDN participant. 

Sharing information on this website is not a requirement of UDN participation. Only descriptions about participants who give explicit consent will appear here.

Date of Report

Jul 01, 2016

Full Name

Additional sex combs-like 2

Location
Chromosome 2 (2p23.3)


Function

The ASXL2 gene is the human homolog of the Drosophila asx gene. The asx gene enhances the function of a gene that codes for a protein involved in transcriptional activation and silencing (Katoh and Katoh, 2003).

Database Links

GeneCards: GC02M025733

Genetics Home Reference: ASXL2 gene

NCBI Gene: 55252

OMIM: 612991

UniProtKB/Swiss-Prot: Q76L83

Clinical Significance

A change in the ASXL2 gene was identified in a UDN participant and other patients with similar symptoms (Shashi et al, 2016 ).

The participant, an 8-year-old male who is larger than average (macrosomia) and has atypical facial features (including a large birthmark on his forehead (glabellar hemangioma)), a decrease in brain white matter (cerebral white matter atrophy), learning difficulties, and mild developmental delays was found to carry the following de novo genetic variant in the ASXL2 gene: c.2424delC/p.P808fs.

Gene ASXL2
Inheritance Pattern Autosomal dominant
Position Chr2:25966781
Transcript NM_018263
DNA Change c.2424delC
Protein Change p.P808fs

Since infancy, the patient’s height, weight and head circumference have been above the 95th percentile, and X-rays have shown advanced bone age. He had two heart problems (ventricular septal defect, patent ductus arteriosus) that resolved on their own. At age 5, he was diagnosed with weak cartilage in the walls of his trachea and bronchial tubes (tracheomalacia and bronchomalacia). Currently he has a slightly prolonged QT interval, sleep apnea, and elevated liver enzymes (transaminases).

The patient also has atypical facial features, including a large birthmark on his forehead (glabellar hemangioma), widely spaced eyes (hypertelorism), a flat nasal bridge, slightly downslanting eyes (palpebral fissures), and small ears. He also has multiple small birthmarks (capillary hemangiomas) on his chest, upper arms, and neck.

Developmentally, the patient has shown learning difficulties and aggressive behavior.

Some of his other features include:

  • Mild accumulation of fat in the liver (mild hepatic steatosis)
  • Elevated liver enzymes (transaminases)
  • Seizures during fever (febrile seizures)
  • High insulin and lipid levels (hyperinsulinemia, hyperlipidemia)
  • Insulin resistance
  • Abnormal copper balance (abnormality of copper homeostasis)
  • Mild sleep apnea (obstructive)
  • Cupped and round ear
  • High palate
  • Skin of upper eyelid covers inner corner of eye (epicanthus)
  • Droopy eyes (ptosis)
  • Abnormality of the cornea (ovoid shaped corneas, horizontal>vertical)
  • Features of autism
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