Dup15q syndrome is the common name for chromosome 15q11.2-q13.1 duplication syndrome. This is a neurodevelopmental disorder, caused by the partial duplication of Chromosome 15, that confers a strong risk for autism spectrum disorder, epilepsy, and intellectual disability.It is the most common genetic cause of autism, accounting for approximately 1-3% of cases.Dup15q syndrome includes both interstitial duplications and isodicentric duplications.

Dup15q syndrome is caused by copy number variation (CNV) in which extra copies of certain genes are present in the genome. Two duplication types are commonly described in Dup15q syndrome, interstitial and isodicentric. Interstitial duplications are typically partial trisomies (i.e., one extra copy of each gene) and features these extra gene copies on the Chromosome 15 alongside the "original" copies. Isodicentric duplications are typically partial tetrasomies (i.e., two extra copies of each gene) and feature an extranumerary chromosome that contains the extra genes.

Chromosome 15 is one of the 23 pairs of chromosomes in humans. Humans are born with 2 copies of each chromosome – 1 from the mother (maternal) and 1 from the father (paternal). Depending on which parental chromosome the extra genetic material is on, symptoms may present differently. In most cases of chromosome 15q11.2-13.1 duplication syndrome, the chromosome duplication is not inherited, but de novo, which means the multiplication occurred as a random event during early embroyonic development.

Symptoms include

HYPOTONIA

Babies with dup15q usually have hypotonia (poor muscle tone). They may appear “floppy” and have difficulty sucking and feeding. Motor milestones such as rolling over, sitting up, and walking are significantly delayed. 

FACIAL FEATURES

Many individuals with dup15q syndrome share similar facial characteristics. These include a flat nasal bridge which gives them a “button” nose. There may be skin folds, called “epicanthic”, at the inner corners of the eyes, and the eyes may be deep set. Ears may be low-set and/or posteriorly rotated. There may also be noticeable unfolding of the edge of the ears. The palate (roof of the mouth) may be unusually high. 

SPEECH/LANGUAGE

Most children with dup15q are affected by speech/language delays. Expressive language may be absent or may remain very poor and is often echolalic with immediate and delayed echolalia and pronoun reversal.

SEIZURE DISORDERS

Seizures represent an important medical feature of dup15q syndrome. Over half of all people with idic(15) will have at least one seizure. The majority of those will experience their first seizure before age 5, but seizure onset occurs up through puberty and young adulthood in this population. There are many different types of seizures experienced by individuals with dup15q syndrome. Affected individuals may start with one seizure type, with other types emerging as the individual ages.

OTHER MEDICAL PROBLEMS

Other reported medical problems include recurrent respiratory infections in childhood, middle ear effusions requiring tubes, eczema, precocious puberty, other menstrual irregularities, overeating, weight gain and Scoliosis.