COMP Gene

Multiple epiphyseal dysplasia is a disorder of cartilage and bone development primarily affecting the ends of the long bones in the arms and legs (epiphyses). There are two types of multiple epiphyseal dysplasia, which can be distinguished by their pattern of inheritance. Both the dominant and recessive types have relatively mild signs and symptoms, including joint pain that most commonly affects the hips and knees, early-onset arthritis, and a waddling walk. Although some people with multiple epiphyseal dysplasia have mild short stature as adults, most are of normal height. The majority of individuals are diagnosed during childhood; however, some mild cases may not be diagnosed until adulthood.

Recessive multiple epiphyseal dysplasia is distinguished from the dominant type by malformations of the hands, feet, and knees and abnormal curvature of the spine (scoliosis). About 50 percent of individuals with recessive multiple epiphyseal dysplasia are born with at least one abnormal feature, including an inward- and upward-turning foot (clubfoot), an opening in the roof of the mouth (cleft palate), an unusual curving of the fingers or toes (clinodactyly), or ear swelling. An abnormality of the kneecap called a double-layered patella is also relatively common.

Pseudoachondroplasia is an inherited disorder of bone growth. It was once thought to be related to another disorder of bone growth called achondroplasia, but without that disorder's characteristic facial features. More research has demonstrated that pseudoachondroplasia is a separate disorder.

All people with pseudoachondroplasia have short stature. The average height of adult males with this condition is 120 centimeters (3 feet, 11 inches), and the average height of adult females is 116 centimeters (3 feet, 9 inches). Individuals with pseudoachondroplasia are not unusually short at birth; by the age of two, their growth rate falls below the standard growth curve.

Other characteristic features of pseudoachondroplasia include short arms and legs; a waddling walk; joint pain in childhood that progresses to a joint disease known as osteoarthritis; an unusually large range of joint movement (hyperextensibility) in the hands, knees, and ankles; and a limited range of motion at the elbows and hips. Some people with pseudoachondroplasia have legs that turn outward or inward (valgus or varus deformity). Sometimes, one leg turns outward and the other inward, which is called windswept deformity. Some affected individuals have a spine that curves to the side (scoliosis) or an abnormally curved lower back (lordosis). People with pseudoachondroplasia have normal facial features, head size, and intelligence.