Search for a rare disease
Other search option(s)
A spondylodysplasic dysplasia clinically characterized by postnatal progressive vertebral fusions frequently manifesting as block vertebrae, contributing to an shortened trunk and hence disproportionate short stature, scoliosis, lordosis, carpal and tarsal synostosis and infrequently, club feet.
ORPHA:3275Classification level: Disorder
Spondylocarpotarsal synostosis (SCT) is very rare. To date, less than 40 cases have been reported in the medical literature.
While the clinical onset is postnatal, the diagnosis becomes clinically evident in early in childhood. Primary clinical characteristics of SCT syndrome include progressive vertebral fusions manifesting as block vertebrae leading to a shortened trunk resulting in disproportionate short stature that becomes apparent with physical growth. Scoliosis, lordosis, carpal and tarsal synostosis are frequent with club feet being observed in a minority of cases. A mild facial dysmorphism with a round face with frontal bossing and anteverted nostrils can be evident. Midline cleft palate, conductive hearing loss, joint laxity and dental enamel hypoplasia are uncommonly reported.
SCT syndrome is due to biallelic mutations in FLNB (localized to 3p14.3) that encodes cytoskeletal protein filamin B. A very similar condition is caused by either monoallelic or biallelic mutations in MYH3.
Diagnosis is confirmed by skeletal x-rays and genetic testing. Radiographs demonstrate progressive vertebral fusions and lumbar spine, carpal and tarsal synostosis without rib anomalies. Occasionally, delayed ossification of epiphyses and bilateral epiphyseal femur dysplasia are reported.
Differential diagnosis may include isolated Klippel-Feil syndrome and other vertebral dysplasias, such as autosomal dominant spondylocostal dysplasia and multiple synostoses syndrome.
SCT syndrome follows an autosomal recessive inheritance (FLNB, MYH3) or occasionally autosomal dominant inheritance (MYH3). Genetic counseling should be proposed to at risk couples informing them that there is 25% (autosomal recessive) or 50% (autosomal dominant) risk of tranmitting the disease to offspring.
Management and treatment
Management involves ophthalmologic, audiologic and spine assessments. Scoliosis is treated medically; no effective surgical intervention has been described. The cervical spine should be evaluated for features of instability prior to general anesthesia. Pain management is indispensable as patients suffer from much continuing physical pain due to the spinal deformities and fused block vertebrae.
It has not been formally evaluated if SCT syndrome affects life expectancy.
- Clinical genetics review
- English (2020)