- See: Achondroplasia

- Discussion:
    - autosomal dominant disorder which occurs as a result of a mutation of a calmodulin like calcium binding protein;
    - result is abnormal proteoglycan accumulation in the chondrocyte rough endoplasmic reticulum;
    - there are moderate to severe epiphyseal, metaphyseal, and physeal abnormalities in long bones, as well as spinal involvement;
    - subtypes:
            - four subtypes have been proposed: two with autosomal inheritance (I, III) and two with recessive inheritance (II, IV);
            - there will be variable severity of skeletal involvement (type I is often mild vs type IV which is the most severe);

- Clinical Features:
    - condition is not recognized at birth, but growth retardation is apparent by the age of 2 or 3 years;
           - at that time, rhizomelic shortening of the extremities is evident;
    - dwarfism can easily be differentiated from achondroplasia by the normal face and skull, and the absence of interpedicular narrowing of the lumbar spine;
           - face and head have normal appearance & trunk is normal except for exaggerated lumbar lordosis;
    - adult height ranges from 106 to 130 cm.
    - extremities:
           - long bones are characterized by epiphyseal, metaphyseal, and physeal changes;
                  - this uneven growth leads to joint incongruity and malalignment;
           - precocious arthritis is a major complication, as in other epiphyseal dysplasias;
           - coxa vara is relatively mild but may lead to deformity, lateral subluxation, and incongruity;
    - spine:
           - cervical spine atlantoaxial instability may occur and is worked up in the usual manner (flexion and extension views);
                  - atlantoaxial fusion is procedure of choice if instability causes symptoms;
           - progressive thoracolumbar kyphosis may occur but is much less severe than that seen in achondroplasia;
                  - angular or vertebral wedging or kyphosis may result from several less involved vertebral bodies

Pseudoachondroplastic dwarfism: A rough-surfaced endoplasmic reticulum storage disorder.   

Pseudoachondroplasia: Biochemical and histochemical studies of cartilage

Disorders of the Pediatric and Adolescent Spine.  Spinal Manifestations of Skeletal Dysplasias.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, May 14, 2012 4:03 pm