Babies born with this disorder may have respiratory problems and are typically small at birth. They often have an underdeveloped larynx resulting in the characteristic cat-like cry. Patients also have very distinctive features. These include an unusually round face, widely set eyes, small bridge of the nose, a small head, a small chin, and folds of skin over the eyes.
Other symptoms include heart defects, sight or hearing problems, skeletal or muscular problems, or poor muscle tone. They tend to have problems talking and walking correctly. Severe mental retardation and behavior problems, such as aggression and hyperactivity can occur. However, even with all of these problems, patients have a normal life expectancy.