Chromosomes seen in Klinefelters

These are the chromosomes seen in K. Klinefelter syndrome is a genetic condition that results when a boy is born with an extra copy of the X chromosome. Klinefelter syndrome is a genetic condition affecting males, and it often isn't diagnosed until adulthood. Males born with Klinefelter syndrome may have low testosterone and reduced muscle mass, facial hair, and body hair. Most males with this condition produce little or no sperm. Klinefelter syndrome may adversely affect testicular growth, resulting in smaller than normal testicles, which can lead to lower production of testosterone. The syndrome may also cause reduced muscle mass, reduced body and facial hair, and enlarged breast tissue. The effects of Klinefelter syndrome vary, and not everyone has the same signs and symptoms. Most men with Klinefelter syndrome produce little or no sperm, but assisted reproductive procedures may make it possible for some men with Klinefelter syndrome to father children. Products & Services A Book: Mayo Clinic Family Health Book Show more products from Mayo Clinic Symptoms Signs and symptoms of Klinefelter syndrome vary widely among males with the disorder. Many boys with Klinefelter syndrome show few or only mild signs. The condition may go undiagnosed until adulthood or it may never be diagnosed. For others, the condition has a noticeable effect on growth or appearance. Signs and symptoms of Klinefelter syndrome also vary by age. Babies Signs and symptoms may include: Weak muscles Slow motor development — taking longer than average to sit up, crawl and walk Delay in speaking Problems at birth, such as testicles that haven't descended into the scrotum Boys and teenagers Signs and symptoms may include: Taller than average stature Longer legs, shorter torso and broader hips compared with other boys Absent, delayed or incomplete puberty After puberty, less muscle and less facial and body hair compared with other teens Small, firm testicles Small penis Enlarged breast tissue (gynecomastia) Weak bones Low energy levels Tendency to be shy and sensitive Difficulty expressing thoughts and feelings or socializing Problems with reading, writing, spelling or math Men Signs and symptoms may include: Low sperm count or no sperm Small testicles and penis Low sex drive Taller than average height Weak bones Decreased facial and body hair Less muscular compared with other men Enlarged breast tissue Increased belly fat When to see a doctor See a doctor if you or your son has: Slow development during infancy or boyhood. Delays in growth and development can be the first sign of a number of conditions that need treatment — including Klinefelter syndrome. Though some variation in physical and mental development is normal, it's best to check with a doctor if you have any concerns. Male infertility. Many men with Klinefelter syndrome aren't diagnosed with infertility until they realize they're unable to father a child. Request an appointment From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview. Enter your email EmailLearn more about Mayo Clinic’s use of data. Subscribe! Causes Klinefelter syndrome occurs as a result of a random error that causes a male to be born with an extra sex chromosome. It isn't an inherited condition. Humans have 46 chromosomes, including two sex chromosomes that determine a person's sex. Females have two X sex chromosomes (XX). Males have an X and a Y sex chromosome (XY). Klinefelter syndrome can be caused by: One extra copy of the X chromosome in each cell (XXY), the most common cause An extra X chromosome in some of the cells (mosaic Klinefelter syndrome), with fewer symptoms More than one extra copy of the X chromosome, which is rare and results in a severe form Extra copies of genes on the X chromosome can interfere with male sexual development and fertility. Risk factors Klinefelter syndrome stems from a random genetic event. The risk of Klinefelter syndrome isn't increased by anything a parent does or doesn't do. For older mothers, the risk is higher but only slightly. Complications Klinefelter syndrome may increase the risk of: Anxiety and depression Social, emotional and behavioral problems, such as low self-esteem, emotional immaturity and impulsiveness Infertility and problems with sexual function Weak bones (osteoporosis) Heart and blood vessel disease Breast cancer and certain other cancers Lung disease Metabolic syndrome, which includes type 2 diabetes, high blood pressure (hypertension), and high cholesterol and triglycerides (hyperlipidemia) Autoimmune disorders such as lupus and rheumatoid arthritis Tooth and oral problems that make dental cavities more likely Autism spectrum disorder A number of complications caused by Klinefelter syndrome are related to low testosterone (hypogonadism). Testosterone replacement therapy reduces the risk of certain health problems, especially when therapy is started at the beginning of puberty. By Mayo Clinic Staff Request an appointment Diagnosis & treatment Sept. 21, 2019 Print Show references Related Associated Procedures Genetic testing Psychotherapy Products & Services A Book: Mayo Clinic Family Health Book Show more products and services from Mayo Clinic Advertisement Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. Advertising & Sponsorship PolicyOpportunitiesAd Choices Mayo Clinic Press Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press. 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