1p36 deletion syndrome

,1p36 deletion syndrome (also known as monosomy 1p36) is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features. The symptoms may vary, depending on the exact location of the chromosomal deletion.

The condition is caused by a genetic deletion (loss of a segment of DNA) on the outermost band on the short arm (p) of chromosome 1. It is one of the most common deletion syndromes. It is estimated that the syndrome occurs in one in every 5,000 to 10,000 births. Knowledge of the disorder has increased a great deal over the last decade, mainly because more patients have been accurately diagnosed and described in international medical literature.

Characteristics

The facial features of 1p36 deletion syndrome have been considered to be characteristic, although few patients have been diagnosed solely on the basis of facial appearance. These features may include microcephaly, small, possibly slanted, deep-set eyes, a flat nose and nasal bridge, anomalous, low-set and small ears, a small mouth with down-turned corners and a pointed chin. Distinguishing features in another study were a large or late-closing anterior fontanelle (up to 85% of patients) and facial asymmetry.

History 

The first cases of 1p36 deletion syndrome were described in the 1980s. However, since many of these individuals also had other chromosomal imbalances, symptoms varied widely. The reason it took so long to recognize the condition as a distinct chromosome deletion syndrome is that the deletions causing the disorder are too small to be detected in a routine chromosomal analysis. FISH (fluorescent in situ hybridization) and DNA-based technology known as MLPA (multiple ligation probe amplification) used in testing have aided in diagnosing an increasing number of cases since the 1990s.