Larsen syndrome is a disorder that affects the development of bones throughout the body. The signs and symptoms of Larsen syndrome vary widely even within the same family. Affected individuals are usually born with dislocations of the hips, knees, or elbows. Foot abnormalities, such as inward- and upward-turning feet (clubfeet), are also common. Affected individuals generally have small extra bones in their wrists and ankles that are visible on x-ray images. The tips of their fingers, especially the thumbs, are typically blunt and square-shaped (spatulate).

Characteristic facial features in people with Larsen syndrome include a prominent forehead (frontal bossing), flattening of the bridge of the nose and middle of the face (midface hypoplasia), and wide-set eyes (ocular hypertelorism). Many people with Larsen syndrome have an opening in the roof of the mouth (a cleft palate). Affected individuals may also have hearing loss caused by malformations in tiny bones in the ears (ossicles).

Short stature is a common feature of Larsen syndrome. In addition, people with the condition may have an unusually large range of joint movement (hypermobility) or joint deformities (contractures) that restrict movement. People with Larsen syndrome can also have abnormal curvature of the spine (kyphosis or scoliosis) that can impair breathing or compress the spinal cord and lead to weakness of the limbs. Some affected individuals experience respiratory problems, such as partial closing of the airways, short pauses in breathing (apnea), and frequent respiratory infections. Heart and kidney problems can also occur in people with Larsen syndrome. People with this condition can survive into adulthood. Their intellectual function is usually unaffected.

• Joint dislocation (especially of the hips, knees, and elbows)
• Hypermobile joints
• Characteristic face such as flat, rectangular face, depressed nasal bridge, prominent forehead, and widely spaced eyes (hypertelorism)
• Long fingers with broad ends (spatula-like) especially of the thumbs, and short nails
• Short arms
• Cleft palate
• Clubfoot
• Curved spine (scoliosis and kyphosis) that may compress the spinal cord and lead to weakness of the arms and/or legs, and other problems
• Short stature
• Breathing problems in infancy (due to soft cartilage in the airway)
• Heart (cardiovascular) anomalies
• Hearing loss
• Small extra bones in the wrists and ankles that may be seen in the X-rays.