Pseudoachondroplasia

Pseudoachondroplasia is a bone growth disorder estimated to occur in 1 in 30,000 births. It is characterized by short stature, a large range of joint mobility, joint pain, deformity of the lower legs and often curvature of the spine. There is no relation to achondroplasia as it is a completely separate disorder. Limb deformity is more common than in achondroplasia as well as joint arthritis and scoliosis. Spinal stenosis is not typically present while C1-C2 instability is more common.

Characteristics

Pseudoachondroplasia is characterized by short stature, not initially visible at birth, with adult males typically averaging around 4’ feet in height and adult females around 3’9”. Other 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).

Cause

Pseudoachondroplasia is the result of genetic mutations in the COMP gene which is essential for the normal development of cartilage and for its conversion into bone. Early death of the chondrocytes (bone cells) prevents normal bone growth and causes short stature and bone abnormalities seen in pseudoachondroplasia. In some cases, an affected person inherits the mutation from one affected parent. Most cases (70%) result from new mutations in the gene and occur with no known family history.

Diagnosis

Pseudoachondroplasia is seldom diagnosed at birth due to the absence of short stature during that period. Instead, its unique characteristics manifest gradually over time, setting it apart from other forms of dwarfism. Diagnosis is confirmed by clinical examination, x-rays and genetic testing. An amniocentesis can be used to diagnose a child in utero.

Management

Spinal Deformity: Mild forms of spine curvature, such as scoliosis and kyphosis, may not require surgical intervention, severe cases have shown positive outcomes with surgical correction. Cervical instability, a more serious issue, requires immediate surgical intervention.

Joint Disease: Due to malalignment, hypermobility and restricted motion, joint pain begins early on in childhood. Physical therapy and prescription medications can improve joint motion and help to avoid muscle degeneration or atrophy. Surgical deepening of the hip sockets can help relieve restricted mobility and total hip replacements are performed in more than 50% of individuals living with pseudoachondroplasia.

Limb/Bone Deformity: Early on, a child's own growth can be used to straighten the bones with a minimal surgery. An osteotomy (cutting the bone) can also be used to straighten the limbs. Some form of surgical intervention is typically required before adulthood.

Obesity: Measures to avoid obesity should begin in early childhood. Standard weight-by-height grids specific for achondroplasia should be used to monitor progress.

Support and Resources

Supportive Community: Join our community of individuals, families, and medical professionals who understand and support those living with pseudoachondroplasia.

Educational Materials: Access a wealth of educational resources, including articles, videos, and guides to help you navigate life with pseudoachondroplasia.

MAGIC Foundation Events: Stay updated on upcoming events, conferences, and support groups near you.