Patients appear normal at birth and growth
retardation is seldom recognized until the second year of life when the body
proportions may resemble classical achondroplasia. Skeletal lesions occur as
a result of stresses on soft epiphyseal cartilage. Thus, at sites such as
the anterior vertebral margins, and the wrists, ankles, and knee joints,
there may be severe cartilaginous deformity. Sites not subjected to
excessive stress, such as the base of skull, face, sacrum, and central
portions of the vertebrae, appear relatively normal. Unlike achondroplasia,
head size is normal for age and the face appears normal. Intelligence is not
affected. Lumbar lordosis, kyphosis, and scoliosis may all occur. Waddling
gait. There may be atlantoaxial dislocation and odontoid hypoplasia. The
fingers are hyperlax and short, and do not show the trident configuration
typical of achondroplasia. Ligamentous laxity contributes to the leg
deformities (from genu varum to genu valgum). Chronic compression myelopathy
of the cervical cord as a consequence of chronic atlantoaxial dislocation
has been reported. Extraskeletal complications are uncommon. Adult height
ranges from 80 to 130 cm (31.5 to 51.2 inches).