Spondyloepimetaphyseal Dysplasia (SEMD) describes
a group of disorders which have major radiological abnormalities of the
spine, epiphyses, and metaphyses in common. Multiple forms exist and the
phenotypes, modes of inheritance, and radiographic abnormalities vary
Spondyloendochromatosis; Camera Stella
Syndrome; Leonard Hughes Syndrome.
Strudwick type of SEMD (Strudwick Syndrome)
- SEMD with Joint Laxity
- SEMD with Micromelia
- SEMD Iraqi type (Sohat type of SEMD)
- SEMD Irapa type
- SEMD type II
- X-linked type of SEMD
- Sponastrime Dysplasia
- SEDM with Short Limbs and Abnormal Calcifications
- SEMD with Multiple Joint Dislocations (Hall type of SEMD)
The incidence for spondyloepimetaphyseal dysplasia remains
unknown. However, the overall incidence for all skeletal dysplasias is approximately 1
case per 4000-5000 births in the USA. However, some authors have suggested that the
true incidence may be twice as high because many skeletal dysplasias do not manifest
clinically until the individual is diasgnosed with short stature, joint symptoms, or
other complications that arise during childhood. Lethal skeletal dysplasias are estimated
to occur in 0.95 per 10,000 live births. The 4 most common skeletal dysplasias are
thanatophoric dysplasias, achondroplasia, osteogenesis imperfecta, and achondrogenesis.
Thanatophoric dysplasia and achondrogenesis account for 62% of all lethal skeletal
dysplasias. Achondroplasia is the most common nonlethal skeletal dysplasia.
Autosomal dominant inheritance is found in
Strudwick type of SEMD and SEMD with Multiple Dislocations. Autosomal
recessive transmission occurs in SEMD with Joint Laxity, Iraqi type of SEMD,
Irapa type of SEMD, Short Limb-Abnormal Calcification type of SEMD, and
Sponastrime Dysplasia. X-Linked SEMD is likely to be inherited in an
(X-linked) dominant manner. Inheritance in the Micromelic type of SEDM has
not been determined, yet.
Skeletal dysplasias are characterized by abnormal
growth of bone and cartilage. Involvement of both the epiphyses and
metaphyses distinguishes the Spondyloepimetaphyseal Dysplasias from the
Spondylometaphyseal Dysplasias and the Spondyloepiphyseal Dysplasias.
Clinical syndromes with characteristic radiological
findings. In utero ultrasonography may identify limb abnormalities but is
The clinical features depend on the type of SEMD
and the age of the patient.
Strudwick type of SEMD presents at birth with cleft palate, short limbs and trunk, protruding
abdomen, and respiratory distress secondary to small chest with short ribs.
Other clinical features include hypertelorism and a flat face. Intelligence and life
expectancy are normal. Features occurring later on in life include severe
coxa vara (with possible dislocation), a waddling gait, lumbar hyperlordosis
(platyand anisospondyly) and myopia with retinal detachment. Before these
children reach school age, the characteristic changes in the metaphyses of
the long bones become evident, which usually affect the ulna more severely
than radius, fibula, or tibia. The disorder manifests as fragmentation of the
long bone metaphyses mixed with areas of sclerosis. Lung function tends to
remain compromised, even more so if kyphoscoliosis develops. Cervical spine
instability may be present because of hypoplasia of C3 and/or the odontoid
process. The genetic defect ...