Microcephalic osteodysplastic primordial dwarfism type I (MOPD1) is a severe autosomal recessive skeletal dysplasia characterized by dwarfism, microcephaly, and neurologic abnormalities, including mental retardation, brain malformations, and ocular/auditory sensory deficits. Patients often die in early childhood (summary by Pierce and Morse, 2012).

CHST3-related skeletal dysplasia is characterized by short stature of prenatal onset, joint dislocations (knees, hips, radial heads), clubfeet, and limitation of range of motion that can involve all large joints. Kyphosis and occasionally scoliosis with slight shortening of the trunk develop in childhood. Minor heart valve dysplasia has been described in several persons. Intellect and vision are normal.

The Isidor-Toutain type of spondyloepimetaphyseal dysplasia (SEMDIST) is characterized by normal birth length, early postnatal growth deficiency, severe short stature, and genu varum. Skeletal radiographs show platyspondyly and severe epiphyseal and metaphyseal changes in the lower limbs (Le Caignec et al., 2019).