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
