Saethre-Chotzen Syndrome

A number sign (#) is used with this entry because of evidence that the Saethre-Chotzen syndrome (SCS) is caused by heterozygous mutation in the TWIST1 gene (601622) on chromosome 7p21.

See also Muenke syndrome (602849), which is caused by a mutation in the FGFR3 gene (P250R; 134934.0014) and has a similar overlapping phenotype to SCS. In addition, at least 1 individual with a phenotype of SCS has been described with a mutation in the FGFR2 gene (176943.0023).

Description

Saethre-Chotzen syndrome is characterized by craniosynostosis, facial dysmorphism, and hand and foot abnormalities. Coronal synostosis resulting in brachycephaly is the most frequent cranial abnormality observed, and the most common facial features are asymmetry, hypertelorism, and maxillary hypoplasia. Other features include high forehead, low frontal hairline, late-closing fontanel, strabismus, ptosis, lacrimal duct stenosis, deviated nasal septum, small low-set posteriorly rotated ears with prominent crus, and hearing loss. The limb anomalies consist of radioulnar synostosis, brachydactyly, cutaneous syndactyly, and hallux valgus. Patients also exhibit short stature and vertebral fusion, and mild to moderate mental retardation has been noted in some cases. Inter- and intrafamilial variability is significant, with some patients having fusion of other sutures, or no apparent craniosynostosis but abnormal skull morphology. The degree of syndactyly is also variable, and digital abnormalities can be absent (Jabs, 2008).

Clinical Features

In the family described by Saethre (1931), a mother, 2 daughters, and probably other maternal relatives showed mild acrocephaly, asymmetry of the skull, and partial soft tissue syndactyly of fingers 2 and 3 and toes 3 and 4. Chotzen (1932) found identical malformations in a father and 2 sons. Bartsocas et al. (1970) described a Lithuanian kindred living in the United States in which 10 persons in 3 generations were affected, with several instances of male-to-male transmission. Waardenburg et al. (1961) reported asymmetry of the skull and orbits (plagiocephaly), strabismus, and a thin, long, pointed nose in 6 generations of a kindred. Some affected persons had bifid terminal phalanges of digits 2 and 3 and absence of the first metatarsal. Cleft palate, hydrophthalmos, cardiac malformation, and contractures of elbows and knees were present in some.

Aase and Smith (1970) described a syndrome comprising asymmetry of the face (hypoplasia of the left side), unusually shaped ear with prominent crus (see their Figure 2), and simian crease in 5 members of 3 generations (with 1 instance of male-to-male transmission). They pointed out similarities to and differences from the asymmetry of the face and skull with abnormalities of the digits described by Waardenburg et al. (1961). Gorlin (1971) thought the syndrome described by Aase and Smith (1970) was Chotzen syndrome. Carter et al. (1982) recognized 9 patients, including familial cases. Like Aase and Smith (1970), they recognized a long and prominent ear crus as a valuable sign.

Kurczynski and Casperson (1988) described mother and daughter with craniosynostosis and symmetrical syndactyly involving the fourth and fifth toes. In addition, both had a short columella and small pinnae. Kurczynski and Casperson (1988) concluded that this represented a new form of acrocephalosyndactyly and suggested the designation auralcephalosyndactyly (109050).

Legius et al. (1989) described mother and son with bilateral symmetrical syndactyly of the third, fourth and fifth toes, mild craniosynostosis, and small pinnae. In addition, the mother had fusion of 2 cervical vertebrae and partial duplication of the first metatarsal. Furthermore, the distal phalanges of both great toes were bifid. These skeletal changes in combination with cutaneous syndactyly of the toes, abnormal auricles, and acrocephaly have been described in the Saethre-Chotzen syndrome (Kopysc et al., 1980) and also in the Robinow-Sorauf syndrome (180750) (Carter et al., 1982). Legius et al. (1989) concluded that the Saethre-Chotzen, aurolcephalosyndactyly, and Robinow-Sorauf syndromes may be somewhat different expressions of the same dominant gene.

Marini et al. (1991) presented a family illustrating the mild and easily missed expression of the gene in a parent. Niemann-Seyde et al. (1991) observed ACS III in 9 members of 4 generations of a family; 5 of them were severely affected. Russo et al. (1991) described a case of renotubular dysgenesis (267430) in an infant who had widely patent cranial fontanels and whose father and sister showed acrocephalosyndactyly of the Saethre-Chotzen type. This was probably a coincidental association between a recessive disorder and a dominant disorder.

Chun et al. (2002) found that 3 patients clinically identified as having the Saethre-Chotzen phenotype, 2 with a TWIST mutation and 1 with a TWIST deletion, had the unusual feature of anal malposition/stenosis.

Kress et al. (2006) identified mutations in the TWIST1 gene in 71 patients from 39 of 124 pedigrees with coronal suture synostosis. Fourteen novel mutations were identified. By comparison of clinical features with 42 patients from 24 kindreds with Muenke syndrome and the FGFR3 P250R mutation, classic SCS could be distinguished from the Muenke phenotype by presence of low-set frontal hairline, gross ptosis of the eyelids, subnormal ear length, dilated parietal foramina, interdigital webbing, and broad great toe with bifid distal phalanx. Patients with SCS also tended to have intracranial hypertension as a consequence of early progressive multisutural fusion and normal mental development; those with Muenke syndrome tended to have mental delay and sensorineural hearing loss. Kress et al. (2006) concluded that SCS and Muenke should be considered separate syndromes.

Other Features

Sahlin et al. (2007) found that 15 (52%) of 29 women over the age of 25 with Saethre-Chotzen syndrome from 15 families developed breast cancer. At least 4 patients developed breast cancer before age 40, and 5 between 40 and 50. The authors concluded that breast cancer is a previously unrecognized symptom of the disorder and further suggested that the TWIST1 gene may be a breast cancer susceptibility gene.

Mapping

Brueton et al. (1992) presented molecular genetic linkage studies suggesting localization of the gene for the Saethre-Chotzen syndrome on distal 7p. Sixteen families with involvement in 2 or more generations were available for study. One of their families (number 16) had characteristics suggesting the Jackson-Weiss syndrome (123150). Excluding this family and pedigree number 15 which had a Pfeiffer-like syndrome (101600), Brueton et al. (1992) found tight linkage to D7S370 (maximum lod = 3.00 at theta = 0.00) and with D7S10 (maximum lod = 2.39 at theta = 0.00). The relationship to other forms of craniosynostosis with hand anomalies that map to 7p remains to be determined. In linkage analysis on 6 ACS III families using 5 CA repeat polymorphisms from 7p, Malcolm et al. (1993) found evidence suggesting location between D7S493 and D7S516. Two patients, a father and daughter, were found with ACS III and a balanced translocation t(7;10)(p21;q21.2). Reid et al. (1993) reported 2 additional patients, a male infant and his mother, with an apparently balanced translocation t(2;7)(p23;p22). Lewanda et al. (1994) confirmed linkage of the Saethre-Chotzen syndrome to 7p. The tightest linkage was to D7S493; linkage and haplotype analyses refined the location of the gene to the region between D7S513 and D7S516. On the basis of 4 patients with apparently balanced translocations at 7p21.2, Rose et al. (1994) narrowed the localization of the ACS3 gene to a 6-cM region. By fluorescence in situ hybridization, they showed that the breakpoints were situated within the region flanked by genetic markers D7S488 and D7S493 in distal 7p. Lewanda et al. (1994) used linkage and haplotype analyses to narrow the disease locus to an 8-cM region between D7S664 and D7S507. The tightest linkage was to D7S664; maximum lod = 7.16 at theta = 0.00. Studying the t(2;7)(p23;p22) in a patient with Saethre-Chotzen syndrome, Lewanda et al. (1994) found that the D7S664 locus lay distal to the 7p22 breakpoint, whereas the D7S507 locus was deleted from the translocation chromosome. Wilkie et al. (1995) reported 3 further families, each segregating a different reciprocal chromosomal translocation involving 7p21. A total of 7 apparently balanced carriers were identified and all manifest features of the Saethre-Chotzen syndrome, although only 2 had overt craniosynostosis. In 1 family, the carriers were immediately recognized by their unusual ears, and clefts of the hard or soft palate were present in all 3 families. The abnormally configured ear was pictured in 1 member from each of 3 generations.

Ma et al. (1996) studied 3 further families to provide additional support to the localization of a disease gene between D7S493 and D7S664. There was a suspicion that at least 2 disease-causing genes may map to 7p, one distal and the other proximal to D7S488.

See craniosynostosis (123100) for well-established mapping to 7p21.3-p21.2 on the basis of structural alterations in that region. The gene for Greig cephalopolysyndactyly syndrome (GCPS; 175700) appears to be located at 7p13.

Molecular Genetics

Howard et al. (1997) and El Ghouzzi et al. (1997) demonstrated that the Saethre-Chotzen syndrome results from mutations in the TWIST1 gene (601622). They were prompted to evaluate the TWIST gene, which encodes a basic helix-loop-helix transcription factor, because its expression pattern and mutant phenotypes in Drosophila and mouse are consistent with the SCS phenotype in humans. Howard et al. (1997) mapped the human TWIST gene by PCR analysis of somatic cell hybrids to 7p22-p21 in a region homologous to the region of mouse chromosome 12 where the murine TWIST gene had been mapped. They assigned it to a specific YAC which was known to contain the breakpoint of a chromosome translocation in 1 Saethre-Chotzen syndrome case. Bourgeois et al. (1996) had previously cloned human TWIST and mapped it to 7p21. Howard et al. (1997) identified nonsense, missense, insertion, and deletion mutations in TWIST in patients with Saethre-Chotzen syndrome. El Ghouzzi et al. (1997) reported 21-bp insertions and nonsense mutations in the TWIST gene in 7 probands with SCS.

Paznekas et al. (1998) screened 32 unrelated patients with features of Saethre-Chotzen syndrome for mutations in the TWIST, FGFR2 (176943), and FGFR3 (134934) genes. Nine novel and 3 recurrent TWIST mutations were found in 12 families. Seven families were found to have the FGFR3 P250R mutation (134934.0014), and 1 individual was found to have a VV269-270 deletion of the FGFR2 gene (176943.0023). The detection rate for TWIST or FGFR mutations, including 5 previously reported patients with TWIST mutations, was 68% in Saethre-Chotzen syndrome patients. More than 35 different TWIST mutations had been reported. The most common phenotypic features, present in more than one-third of Saethre-Chotzen patients with TWIST mutations, were coronal synostosis, brachycephaly, low frontal hairline, facial asymmetry, ptosis, hypertelorism, broad great toes, and clinodactyly. Significant intra- and interfamilial phenotypic variability was present for either TWIST or FGFR mutations.

Chun et al. (2002) investigated 11 patients clinically identified as having the Saethre-Chotzen phenotype. Four were found to carry the FGFR3 P250R mutation, 3 were found to be heterozygous for 3 different novel mutations of TWIST, and 2 were found to have a deletion of 1 copy of the entire TWIST gene. Developmental delay was a distinguishing feature of the patients with deletions of TWIST; see CYTOGENETICS section.

Heterogeneity

Saethre-Chotzen Syndrome with Eyelid Anomalies

In a large Indian family reported by Maw et al. (1996) in which BPES (110100) was segregating, Dollfus et al. (2001) found that affected members carried a novel 'stop' mutation in the TWIST gene, gly28 to ter (601622.0011). This form of BPES, which showed linkage to chromosome 7p, had been known as BPES3. After clinical reevaluation of all members of the family, some of whom were not born at the time of the initial linkage analysis, Dollfus et al. (2002) concluded that the phenotypic expression was compatible with Saethre-Chotzen syndrome, with remarkable phenotypic variability. Fifteen of 16 family members examined had moderate to severe ptosis. Eyelid features were the hallmark of the disease for 12 members of the family, suggesting that mutations in TWIST may lead to a phenotype with mainly palpebral features and no craniostenosis. Dollfus et al. (2002) pointed to the previous observations of similar phenotypic variability and eyelid malformation in transgenic twist-null heterozygous mice.

Cytogenetics

Zackai and Breg (1973) described a child who had unicoronal synostosis, unilateral ptosis, short stature, microcephaly, simian crease, developmental delay, and a ring chromosome 7. Zackai and Stolle (1998) reported results that provided an explanation for that patient's findings. Using a combination of techniques, including analysis of microsatellite markers, FISH, and Southern blot analysis, Johnson et al. (1998) determined that a significant proportion of patients with Saethre-Chotzen syndrome had deletions in 7p21.1 that encompass the TWIST gene. Furthermore, patients with large (megabase-sized) deletions in this region have significant learning difficulties in addition to the clinical features of Saethre-Chotzen syndrome, which suggested that such mutations define a new microdeletion syndrome. The findings refined the molecular tools for diagnosis of Saethre-Chotzen syndrome and provided an explanation for at least some of the phenotypic variability that can confound clinical diagnosis of this disorder.

Diagnosis

Johnson et al. (1998) found facial asymmetry, low frontal hairline, and ptosis to be the most helpful for identifying patients with Saethre-Chotzen syndrome in the absence of pathognomonic features such as 2,3 syndactyly of fingers and duplicated halluces. Craniosynostosis and Saethre-Chotzen syndrome may be unicoronal or bicoronal; metopic suture fusion is found in some cases, but sagittal suture fusion is rare. Zackai and Stolle (1998) suggested that it is useful to perform analysis for the P250R mutation in the FGFR3 gene in cases of unicoronal synostosis in which other findings of Saethre-Chotzen syndrome are absent.

History

Reardon and Winter (1994) wrote as follows: 'Clinical geneticists are inured to anecdotes recounting odd presentations of dysmorphic syndromes. Saethre-Chotzen syndrome is a case in point. A consultation for schizophrenia led to the first report from the Norwegian psychiatrist, Haakon Saethre...' (Saethre, 1931). Chotzen (1932) reported a father and 2 sons with the syndrome that came to carry his name.

Zackai and Stolle (1998) reviewed the history of this disorder beginning with the Norwegian psychiatrist Haakon Saethre (1931) and the German psychiatrist F. Chotzen (1932), and continuing with the premolecular nosology, particularly the landmark paper of Pantke et al. (1975), and the molecular characterization through linkage studies and translocation identification, leading to positional cloning, identification of a candidate gene, and the finding of mutations in that gene.