Also known as 49,XYYYY syndrome
What is 49,XYYYY syndrome?
XYYYY syndrome, also known as 49,XYYYY or "X-4-Y", is an extremely rare sex chromosome aneuploidy characterized by the presence of three extra Y chromosomes in males, resulting in a total of 49 chromosomes. There are very few cases reported in the medical literature. Symptoms described include intellectual disability, autism, social anxiety, selective mutism, and separation anxiety disorder. Physical symptoms include facial features, endocrine abnormalities and skeletal malformations.
Who gets 49,XYYYY?
49,XYYYY is an extremely rare sex chromosome aneuploidy with an unknown estimated prevalence.
What causes 49,XYYYY?
49,XYYYY is caused by 3 extra Y chromosomes in boys, most commonly due to the presence of extra chromosomes in the sperm at the time of conception, resulting from nondisjunction (when chromosomes do not divide properly), and is not typically inherited.
How is 49,XYYYY diagnosed?
49,XYYYY is a chromosome condition which can be diagnosed from blood tests. Tests that can diagnose 49,XYYYY include a karyotype (chromosome analysis looking at the number and structure of chromosomes in cells), a chromosomal microarray (a more detailed chromosome study looking for deletions or duplications across all chromosomes) or genetic sequencing (reading through the DNA sequence carried on the chromosomes). 49,XYYYY may be suspected based on physical or neurodevelopmental differences during childhood and can be identified before birth by prenatal screening and/or diagnostic testing, such as an amniocentesis.
What is the treatment for 49,XYYYY?
Treatments for 49,XYYYY are specific to managing symptoms, including testosterone treatment beginning in adolescence to complete puberty and support bone health, monitoring for musculoskeletal abnormalities (imaging or surgery if indicated), therapies for developmental delays, as well as neurodevelopmental, psychological and academic interventions.