Prader-Willi Syndrome (Chromosome 15Q Deletion)

Prader-Willi Syndrome (Chromosome 15q Deletion)

What it is

The Prader-Willi Syndrome (Chromosome 15q Deletion) test is a genetic analysis that detects deletions or abnormalities on the paternal copy of chromosome 15 (region 15q11-q13). Prader-Willi Syndrome (PWS) is a rare genetic disorder characterized by poor muscle tone, feeding difficulties in infancy, developmental delays, excessive appetite in childhood, and risk of obesity. The test confirms the diagnosis by identifying chromosomal deletions or imprinting errors in this region.

Uses

This test is used to confirm a suspected diagnosis of Prader-Willi Syndrome in infants, children, or adults showing typical clinical features. It helps distinguish PWS from other developmental or genetic conditions and guides early intervention, medical management, and genetic counseling for families.

Symptoms That May Lead to the Test

Doctors may recommend this test if you or your child present with:
– Poor muscle tone (hypotonia) and weak cry at birth.
– Feeding difficulties and failure to thrive in infancy.
– Developmental delays and learning difficulties.
– Excessive hunger (hyperphagia) and rapid weight gain in childhood.
– Short stature, delayed puberty, or infertility.
– Behavioral problems such as irritability, stubbornness, or obsessive traits.

Abnormal Results

Positive Result: Detection of a paternal chromosome 15q11-q13 deletion, maternal uniparental disomy (two maternal copies and no paternal copy), or imprinting defect confirms the diagnosis of Prader-Willi Syndrome. This helps establish medical care and genetic counseling.

Negative Result: Suggests no chromosomal deletion detected in this region. However, further molecular testing (such as methylation analysis or uniparental disomy studies) may still be required if clinical suspicion remains high.

Risks

The test requires a blood sample for genetic analysis. Risks are minimal and limited to slight pain, bruising, or dizziness at the puncture site. The laboratory analysis itself carries no direct risk.