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Genetic and Rare Diseases Information Center (GARD)

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48,XXYY syndrome

Other Names for this Disease
  • 48,XXYY Klinefelter syndrome
  • 48,XXYY variant of Klinefelter's syndrome
  • XXYY syndrome
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What are signs and symptoms of 48,XXYY syndrome?

48,XXYY affects various body systems including disruption of male sexual development. Adolescent and adult males with this condition typically have small testes that do not produce enough testosterone, which is the hormone that directs male sexual development. A shortage of testosterone during puberty can lead to reduced facial and body hair, poor muscle development, low energy levels, and an increased risk for breast enlargement (gynecomastia). Because their testes do not function normally, males with 48, XXYY syndrome have an inability to father children (infertility).

48,XXYY syndrome can affect other parts of the body as well. Males with 48,XXYY syndrome are often taller than other males their age. They tend to develop a tremor that typically starts as a young adult and worsens with age. Dental problems are frequently seen with this condition; they include delayed appearance of the primary (baby) or secondary (adult) teeth, thin tooth enamel, crowded and/or misaligned teeth, and multiple cavities. As affected males get older, they may develop a narrowing of the blood vessels in the legs, called peripheral vascular disease. Peripheral vascular disease can cause skin ulcers to form. Affected males are also at risk for developing a type of clot called a deep vein thrombosis (DVT) that occurs in the deep veins of the legs. Additionally, males with 48,XXYY syndrome may have flat feet (pes planus), elbow abnormalities, allergies, asthma, type 2 diabetes, seizures, and congenital heart defects.[1][2]

Most males with 48,XXYY syndrome have some degree of difficulty with speech and language development. Learning disabilities, especially reading problems, are very common in males with this disorder. Affected males seem to perform better at tasks focused on math, visual-spatial skills such as puzzles, and memorization of locations or directions. Some boys with 48,XXYY syndrome have delayed development of motor skills such as sitting, standing, and walking that can lead to poor coordination. Affected males have higher than average rates of behavioral disorders, such as attention deficit hyperactivity disorder (ADHD); mood disorders, including anxiety and bipolar disorder; and/or autism spectrum disorders, which affect communication and social interaction.[1]

Last updated: 5/7/2012

  1. US National Library of Medicine. 48,XXYY syndrome. Genetics Home Reference. January 2010;
  2. Chen H.. Klinefelter syndrome. e-medicine Medscape. May 17, 2011; Accessed 6/23/2011.