Spondylar dysplasia in type X collagenopathy

Further delineation of spondylometaphyseal dysplasia with cone-rod dystrophy

There are several entities that combine a skeletal dysplasia with a retinal dystrophy. Recently, another possibly autosomal recessive entity was added to this group characterized by a specific spondylometaphyseal dysplasia and a cone-rod dystrophy, without other significant impairments. The entity was named SMD-CRD. We further delineate this disorder by reporting on a 16-year-old boy and a pair of twins with this entity. Possible etiologies are discussed. The boy showed low alpha-neuraminidase activity levels in fibroblasts, but normal levels in leucocytes. The meaning of this finding remains as yet unknown.