About Mosaicism

When a person is tested for X&Y variations, many cells are examined. When this test shows that a person has some cells with one number of chromosomes, and other cells have more or fewer chromosomes, we call this being mosaic.

A person can be mosaic with any X or Y variation.

Some people with Klinefelter syndrome have 47,XXY/46,XY mosaicism. While some small studies found those with mosaic XXY have less severe symptoms that those who have XXY in 100% of their cells, we really do not know for sure. Note most people with XXY are not diagnosed during their lives, and XXY is a spectrum condition.

To understand how being mosaic for any X or Y variation may affect you or your loved one we strongly suggesting seeing a genetic counselor or a genetic medicine specialist.

About 48,XXXY

48,XXXY syndrome, also known as XXXY syndrome, is a less common X and Y chromosome condition, affecting between 1 in 17,000 and 1 in 50,000 male births. 48,XXXY is caused when nondisjunction errors occur in the development of the egg or sperm, resulting in a male inheriting two extra copies of the X chromosome.

48,XXXY is associated with a variety of symptoms, but not everyone has the same symptoms or at the same level. Symptoms of 48,XXXY may include:

• Learning problems ranging from learning disabilities to intellectual disability
• Delays and disorders in speech and language
• Delays in motor skills like sitting, standing, and walking and motor coordination difficulties
• Low muscle tone
• Birth defects, more commonly cardiac, genital, or musculoskeletal systems
• Distinctive physical features like wider-set eyes and curvature in pinky fingers
• Irritability, outbursts, and temper tantrums
• Anxiety
• ADHD
• Impaired social skills, social communication problems, autistic traits
• Hypogonadism and infertility
• Risk for gynecomastia
• Average to taller height
• Dental problems
• Neurological problems such as seizures, tremors or motor tics
• Allergies, asthma, and eczema
• Hormone problems including hypothyroidism and diabetes
• Strabismus
• Sleep apnea
• Gastrointestinal problems including reflux, constipation and eosinophilic esophagitis
• Musculoskeletal problems including flat feet, radioulnar synostosis, scoliosis, osteoporosis
• Risks for blood clots
• Impaired adaptive skills

Testing

48,XXXY can be identified  during pregnancy via amniocentesis, CVS, or NIPS (screening test only). A diagnosis of 48,XXXY involves a special genetic test (commonly by blood after birth), typically either a karyotype or a microarray.  These tests can be ordered by most medical providers and are available through most major labs.

Resources

Facebook Support Groups: AXYS XXXY Global Support Group | 48,XXXY Medical Syndrome

48,XXYY, 48,XXXY and 49,XXXXY Syndromes: Not Just Variants of Klinefelter Syndrome

The Story of Rapha, a Boy with 48,XXXY/49,XXXXY

Thinking About Starting Testosterone for XXY/XXYY/XXXY

Klinefelter Syndrome and Other Sex Chromosomal Aneuploidies