OMIM ID:
Spondylometaphyseal Dysplasia, Axial
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Due to the small number of individuals reported, the ocular phenotype is variable and likely incompletely described. Optic atrophy and pigmentary retinopathy are the most consistent findings. The most completely studied individual had evidence of slight bilateral optic nerve atrophy on cerebral MRI imaging as well. There may be extensive RPE atrophy but the fundus pigmentation is usually described as resembling retinitis pigmentosa. The ERG in several patients during the second decade of life already shows severe dysfunction of the photoreceptors, with cones the most severely impacted. In spite of this Goldmann visual fields have been reported to be normal. The macula and OCT have been reported as normal. Telecanthus, nystagmus, hypertelorism, proptosis, and photophobia have been reported. Early onset and progressive visual impairment are characteristic.
Systemic Features
Only 5 patients with this condition have been reported most of whom were short in stature. There may be frontal bossing and the chest is narrow and flattened. Moderate platyspondyly has been described with enlarged but shortened ribs and an irregular iliac crest. Rhizomelic shortening of the limbs is common. The femoral metaphyses are abnormal with their necks shortened and enlarged. The ribs are enlarged but shortened as well and are flared at the ends. Mental development and function are normal.
Genetics
Inheritance
This is an autosomal recessive condition due to homozygous or compound heterozygous mutations in C21orf2.