Ellis-van Creveld Syndrome with hydrometrocolpos is not linked to chromosome arm 4p or 20p

To the Editor:

Ellis-van Creveld (EVC) and McKusick-Kaufman (MKK) syndromes are clinically similar recessively inherited disorders sharing postaxial polydactyly of hands and feet and a distinct congenital heart defect (CHD) [Ellis and Van Creveld, 1940; McKusick et al., 1964]. Distinguishing characteristics are the osteochondrodysplasia and ectodermal anomalies in EVC syndrome, and hydrometrocolpos in MKK syndrome. Phenotypes bridging these two disorders have been described [Akoun and Bagard, 1956; Chitayat et al., 1987]. We have studied two sisters presenting with apparent EVC syndrome, one of whom had also hydrometrocolpos [Digilio et al., 1997a].

Linkage analyses have assigned a locus for EVC syndrome to chromosome region 4p16.1 [Polymeropoulos et al., 1996]. Mutations in the disease-gene, encoding a 992-amino-acid protein, were found in individuals affected by EVC syndrome, and allelism between EVC and Weyers acrodental dysostosis was demonstrated [Ruiz-Perez et al., 2000]. A locus for MKK syndrome was mapped by linkage studies to chromosome region 20p12 [Stone et al., 1998], and mutations of a gene encoding a putative chaperonin were detected in patients with MKK syndrome [Stone et al., 2000]. Interestingly, mutations in the MKK gene have been found in patients with neonatal hydrometrocolpos and polydactyly, who in infancy developed retinal dystrophy and obesity compatible with Bardet-Biedl syndrome [David et al., 1999; Katsanis et al., 2000; Slavotinek and Biesecker, 2000; Slavotinek et al., 2000].

Recently, we reevaluated the two previously reported sisters [Digilio et al., 1997a], and carried out molecular studies to assess an eventual allelic relationship of this phenotype with either the EVC or MKK loci.

Patient 1, a 24-year-old woman, is the first child of healthy non-consanguineous parents. At birth the mother was 23, the father 26-years-old. The baby was born by vaginal delivery at term after an uneventful pregnancy. Birth weight was 3,150 g, length 48 cm, head circumference (OFC) 35.5 cm. Hydrometrocolpos due to vaginal atresia was diagnosed and operated shortly after birth. In addition, she had a narrow thorax, short limbs, and postaxial polydactyly of hands and left foot, with six well formed fingers and toes. Polydactyly was operated at the age of 5 years. Presently, her weight is 54 kg (25th centile), height 156 cm (10th centile), and OFC 53 cm (10th centile). Clinical examination showed median cleft of upper lip (Fig. 1a), oral frenula, high palate, absence of two lower molars, narrow thorax, brachydactyly of fingers, and nail dysplasia (Fig. 1b). Radiographs demonstrated narrow thoracic cage with short ribs (Fig. 1c), short limbs, and brachydactyly. Echocardiographic findings were unremarkable. No abnormality was found at ophthalmologic and audiometric evaluations. Psychomotor development was normal, and cerebral MRI status was normal. Chromosome analysis showed a 46,XX karyotype.

Patient 2, the only sister of patient 1, was born by Cesarean section at term after a normal pregnancy. Birth weight was 3,350 g, length 48 cm, OFC 35 cm. A partial atrioventricular canal defect (AVCD) with a common atrium was diagnosed neonatally. Clinical examination showed median cleft of upper lip, oral frenula, a preauricular tag at right, narrow thorax, short limbs, brachydactyly of fingers, clinodactyly of 5th fingers, nail dysplasia, postaxial polydactyly of hands and feet with well formed fingers and toes. The CHD was corrected at the age of 2 years. The girl is now 12 years old. Her weight is 43 kg (50th–75th centile), height 146 cm (25th centile), OFC 52 cm (25th centile). Oral anomalies include a median cleft of the upper lip (Fig. 2a), frenula, and absence of two lower molars. Hand polydactyly was corrected at the age of 5 years (Fig. 2b); polydactyly of feet is still present (Fig. 2c). Skeletal X-ray examination shows narrow thoracic cage with short ribs (Fig. 2d), short limbs, brachydactyly of hands (Fig. 2e), and polydactyly of feet (Fig. 2f). Neuropsychological development is normal. Results of cerebral MRI, abdominal and pelvis ultrasonography, ophthalmologic and audiologic evaluations were unremarkable. Chromosomes were normal.

The parents showed no physical abnormalities. Their skeletal X-ray findings and echocardiography were normal.

Molecular analysis: dinucleotide repeat markers linked to EVC locus in 4p16.1 and to MKK locus in 20p12 were studied and scored by standard procedures. Two-point linkage analysis was performed using the MLINK program within the LINKAGE package, Version 5.1 [Lathrop and Lalouel, 1984]. The order and genetic distances used for EVC locus are tel-D4S412-0.03cM-HOX7-0.02cM-D4S827-0.01cM-D4S431-cen [Polymeropoulos et al., 1996; Ruiz-Perez et al., 2000]. For the MKK locus the order is tel-D20S175-NM1-D20S894-cen, in a genetic distance of 1 cM [Stone et al., 1998, 2000]. The genetic model used was that of a fully penetrant autosomal recessive trait, and allele frequencies were set as equal.

Two-point LOD scores between chromosome 4 and 20 markers and the disease locus are shown in Table I. The haplotype analysis is indicated in Figure 3a,b. The results show that the locus leading to the EVC/MKK syndrome in our patients is not linked to the 4p16.1 and 20p12 loci. This evidence was supported by haplotype analysis.

The existence of a pathogenetic link between EVC and MKK syndromes has been suspected [Digilio et al., 1997b, 1999a], based on the report of hydrometrocolpos in patients with EVC syndrome [Akoun and Bagard, 1956; Yapar et al., 1996; Digilio et al., 1997a] and narrow thoracic cage and short limbs in individuals with MKK syndrome [Chitayat et al., 1987]. Study of the anatomic types of CHD has supported a clinical overlap between these two syndromes. In fact, AVCD with common atrium occurs as the more frequent cardiac defect in patients with EVC [Digilio et al., 1999a]. MKK syndrome is associated with CHD in 10% of the patients, AVCD or common atrium occurring in about half of the reported patients [Digilio et al., 1999a]. On the basis of CHD, a causal relationship has also been suggested between two groups of disorders presenting with polydactyly, including short rib-polydactyly and oral-facial-digital syndromes [Digilio et al., 1999a]. Allelic mutations or variable deletions of contiguous genes have been considered [Franceschini et al., 1995; Neri et al., 1995].

The genes of EVC and MKK syndromes have been mapped respectively, to chromosome regions 4p16.1 [Polymeropoulos et al., 1996; Ruiz-Perez et al., 2000] and 20p12 [Stone et al., 1998, 2000]. Results of linkage analysis in the present family excludes that the locus for an autosomal recessive EVC plus MKK phenotype is linked to the chromosomal regions of EVC syndrome and MKK syndrome. Thus, this transitional clinical condition, manifesting either as EVC syndrome with hydrometrocolpos or as MKK syndrome with skeletal dysplasia, is not allelic to classic EVC and MKK syndromes and represents an autonomous condition, suggesting heterogeneity in genetic conditions with overlapping EVC and MKK manifestations. A heterozygous mutation in the EVC gene has been found in a father and his daughter presenting with clinical characteristics of EVC syndrome without short stature [Digilio et al., 1995; Ruiz-Perez et al., 2000]. Considering that the sisters of the present report have shared paternal haplotype for chromosome 4, a heterozygous defect cannot be ruled out on the basis of molecular results. Nevertheless, phenotypical, radiological, and echocardiographic evaluations in the father have excluded the presence of abnormalities compatible with EVC syndrome.

A unique clinical expression of an atypical oral-facial-digital syndrome cannot be ruled out in our patients, although oral findings suggestive of oral-facial-digital syndrome, such as cleft or lobulated tongue with nodules, are not present in our patients. Additionally, short ribs and hydrometrocolpos are not part of the classic clinical spectrum of the oral-facial-digital syndromes [Neri et al., 1995].

Anatomical and molecular studies have shown that AVCD is a clinically variable and causally heterogenous condition [Marino et al., 1990; Wilson et al., 1993; Amati et al., 1995; Sheffield et al., 1997; Digilio et al., 1999b]. AVCD with common atrium is rare in non-syndromic patients [Digilio et al., 1999b], while it is quite common in heterotaxia with asplenia [Phoon and Neill, 1994] or polysplenia [Peoples et al., 1983]. Exclusion of the EVC and MKK chromosomal regions in our patients corroborates locus heterogeneity in syndromes with CHD and polydactyly, and also supports genetic heterogeneity of AVCD.