Objective: To analyze the dysmorphological variability and to investigate the presence of mutations in the exon 1 of TWIST gene using direct sequencing in Brazilian families presenting with Saethre-Chotzen Syndrome (SCS).
Methods: Four families with 24 patients diagnosed as having features of SCS were studied. Phenotypic characteristics of all patients were inventoried. The investigation protocol included anamnesis, dysmorphological examination, abdominal ultrasound, spine and cranium x-ray, chromosomal analysis on GTG banding, and screening for mutations in the exon 1 of TWIST gene.
Results: Frequent facial features included brachycephaly (24 of 24), facial asymmetry (20 of 24), prominent ears crus (15 of 24), low-set ears (14 of 24), maxillary hypoplasia (13 of 24), prominent nasal bridge (13 of 24), ptosis of the eyelids (12 of 24), and low-set frontal hairline (12 of 24). Limb abnormalities such as partial hand cutaneous syndactyly (18 of 24), clinodactyly (13 of 24), and broad great toes (13 of 24), and partial cutaneous syndactyly of the feet (9 of 24) were also detected. Among radiological findings were relevant bicoronal (eight of nine) and unicoronal (one of nine) craniosynostosis, digital impressions (eight of nine), bilateral parietal foramina (two of nine), partial fusion 1 and 2 degrees costal arches (two of nine) and bifid spine on lumbar vertebra (two of nine). GTG-banding chromosomal analyses were normal. No TWIST gene mutations were found.
Conclusions: Affected individuals in these four SCS families may carry mutations in other genes of the same developmental pathway. Considering the complexity of the genes involved in skull-limbs development, an accurate dysmorphological evaluation in patients with SCS and their families is especially important for genetic counseling.