Chromosome 1p36 deletion syndrome is a congenital genetic disorder that affects approximately 1 in 5,000 to 1 in 10,000 children born. It is caused by the deletion of the most distal light band of the short arm of chromosome 1. Chromosome 1p36 deletion syndrome can also be called "monosomy 1p36".  The monosomy can be "pure" or can be found in connection withadditional chromosomal imbalance. 

A chromosome is a part of a cell that contains genetic information. Chromosome 1 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 1 is the largest human chromosome and represents about 8 percent of the total DNA in cells. The "p" stands for the short arm of the chromosome or the 'petite' arm. '36' stands for the location of the deletion on the chromosome. Below is a picture of chromosome one.

Chromosome 1p36 Deletion Syndrome is said to be a contiguous gene deletion syndrome. This is a heritable syndrome that result from alterations in a series of genes that are physically close on a chromosome and which, when acting together, normally express certain traits.

Developmental delay affects the majority of children with 1p36 monosomy and is usually severe. Behavioral difficulties and self-injury havebeen described. Hypotonia and feeding problems with oropharyngeal dysphasia are frequent; seizures have been a frequent and debilitating problem. Other dysmorphic, cardiac, visual and auditive features are been described.
 
Patients with a 1p36 deletion have different sized pieces of the chromosome missing and may result in phenotype (characteristic) variability. The seveverity of associated disorders varies, but the physical features are very similar. The clinical features of 1p36 have recently been delineated (represented accurately) and molecular analysis indicates that the occurrences of certain phenotypic (characteristical) features appears to correlate with deletion size.