Jacobs syndrome is a rare chromosomal disorder that affects only males. It is a condition where there is the presence of an extra Y chromosome in all of a male's cells. Males normally have only one X and one Y chromosome, however, individuals with Jacob's syndrome have at least one X and at least two Y chromosomes (XYY). It gives males a total of 47 chromosomes, instead of the average of 46.
Other names for Jacobs syndrome:
- 47, XYY syndrome
- XYY Karyotype
- XYY syndrome
- YY syndrome
- Diplo-Y Syndrome
- Polysomy Y
- Super-male syndrome
This condition is usually asymptomatic which means that it shows no evidence of disease.
In children, 47,XYY may produce some of the following symptoms:
• Delay in developing speech
• Low muscle tone (hypotonia)
• Delayed social development
• Learning disabilities
• Pervasive developmental disorder (PDD-NOS) or mild autism spectrum disorder
• Attention deficit and/or hyperactivity
In older teens and adults, 47,XXY may also be characterized by:
• Very tall stature and long limbs
• Severe acne
• Continued learning and/or social difficulties
• Delay in vocational success
• Anxiety, depression or other mood disorder
• Dental problems
This condition occurs in about 1 in 1,000 newborn boys. Five to 10 boys with 47,XYY syndrome are born in the United States each day.
Diagnosis requires a specialized blood test, called a karyotype or a buccal swab test called
XCAT. In some cases, FISH (fluorescence in situ hybridization), or microarray analysis is performed.
Prenatal diagnosis requires amniocentesis or chorionic villus sampling, or a noninvasive prenatal test called NIPT.
Most cases of 47,XYY syndrome are not inherited. The chromosomal change usually occurs as a random event during the formation of sperm cells. An error in cell division called nondisjunction can result in sperm cells with an extra copy of the Y chromosome. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra Y chromosome in each of the body's cells.
46,XY/47,XYY mosaicism is also not inherited. It occurs as a random event during cell division in early embryonic development. As a result, some of an affected person's cells have one X chromosome and one Y chromosome (46,XY), and other cells have one X chromosome and two Y chromosomes (47,XYY).
Most symptoms can be addressed successfully by early diagnosis and detection, appropriate treatments such as speech and occupational therapy, and special education services, if learning disabilities are involved. Infants and very young children may be eligible for early intervention. Children can benefit from special
education services including;
• Speech therapy
• Occupational and physical therapy when indicated for motor problems
• Special education services or educational accommodations when necessary
• Social skills training programs
• Family or individual counseling
• Behavioral consultation
• Regular exercise and upper body strengthening programs
Adolescents with 47,XYY, may develop severe acne. If so, they should be seen by a dermatologist and treated appropriately to prevent scarring. Adults with 47,XYY, may take several years longer to develop the emotional maturity to become self-supporting and capable of living independently. Interventions that may be helpful for adults with XYY include:
• Psychological counseling when indicated
• Vocational counseling and workplace accommodations when necessary
• Dental health preservation/restoration
• A healthy diet and regular exercise to maintain cardiovascular health