Spondylometaphyseal Dysplasia, Axial
Patient Information
Characteristics
Background and History
This recently described condition is characterized by skeletal abnormalities and a malfunction of the retina in the eye resulting in short stature and visual difficulties among other features.
Clinical Correlations
Visual difficulties such as excessive sensitivity to light and poor vision may be noted during adolescence. Some patients have nystagmus (jerky movements of the eyes). Functional tests of the retina (the tissue in the back of the eye that responds to light) such as the electroretinogram (ERG) reveal decreased responsiveness of the rods and cones. The pigmentation of the retina is abnormal and the optic nerve is usually pale.
There are developmental deformities in the ribs, spinal vertebrae, and proximal bones of the limbs. The result is delayed growth and eventual short stature. The arms and legs appear shortened and the chest is bell-shaped and flat. Mental development and function are normal. The forehead is often prominent.
Genetics
Inheritance
This is an autosomal recessive disorder in which mutations in a specific pair of genes are responsible. The parents are physically normal, carrying the mutation on one member of the pair. However, there is a 25% risk in each child of such parents to inherit both mutations.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis is likely made by a multidisciplinary team of specialists including pediatricians, neurologists, ophthalmologists, and orthopedists. There is no effective treatment for the overall disorder.
Nothing is known regarding longevity. Low vision aids may be helpful, especially in school-age children.
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