Congenital fibrosis of the extraocular muscles type 1 (CFEOM1; OMIM #135700) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. We show that individuals with CFEOM1 harbor heterozygous missense mutations in a kinesin motor protein encoded by KIF21A. We identified six different mutations in 44 of 45 probands. The primary mutational hotspots are in the stalk domain, highlighting an important new role for KIF21A and its stalk in the formation of the oculomotor axis.

Fetuses with cystic hygroma or loose skin of the neck were studied chromosomally and phenotypically to clarify the relation between neck abnormality and cardiovascular malformations. Of 12 fetuses, 9 had chromosome abnormalities: 4 with 45,X, 3 with trisomy 21, one each with trisomy 13, dup 6q. One had normal chromosomes. Two cases, in which chromosome analysis was unsuccessful, were morphologically suspected to be trisomy 13. Nine of the 12 fetuses had either bilateral cystic hygroma of the neck (7 cases) or nuchal bleb (2 cases: trisomy 13 and dup 6q). Two of the 3 remaining cases (trisomy 21) had loose skin of the neck, and one had edematous swelling of the skin of the neck. Except for the last case of trisomy 21, 11 fetuses (91.7%) had severe and/or rare cardiovascular malformations. They were divided into 3 major groups: a) spectrum of hypoplastic left heart syndrome (45,X and dup 6q), b) double outlet right ventricle, agenesis of semilunar valve (trisomy 13), and c) abnormality of atrioventricular orifice or valves (trisomy 21). One fetus with normal chromosomes had persistent left superior vena cava instead of absent right one and calcification of myocardium. Histological observation of edematous skin demonstrated the abnormal distribution of lymph vessels, including their absence. Some cases showed hypoplastic thymus. To integrate the findings of the present study and the descriptions in the literature, a pathogenesis is hypothesized in relation to migration of neural crest cells and extracellular matrix.

Absent semilunar valve was found in three fetal cases with cystic hygroma. Two cases which simultaneously showed absent aortic and pulmonary valves (AAV and APV, respectively) had double-outlet right ventricle. The third case, which lacked only the aortic valve, had atrioventricular septal defect and anomalous origin of the right subclavian artery. Two of the three cases had a markedly hypoplastic thymus. Fifteen AAV and 179 APV cases, including the above-mentioned cases and others reported elsewhere, were discussed with special reference to the pathogenesis of absent semilunar valve. Of the 15 AAV cases, hypoplasia of the left heart was observed in 11 cases (73.3%), double-outlet right ventricle in 5 (33.3%), and aortic arch malformations in 6 (40.0%). In the 179 APV cases, there were 111 tetralogy of Fallot (62.0%) and 44 right-sided aortic arch (24.6%). DiGeorge anomaly was found in one AAV and eight APV cases. These results indicate a pathogenesis that is possibly related to hemodynamic abnormalities or abnormal neural crest cells. Further investigation will be needed to elucidate a more definite pathogenesis of absent semilunar valve.

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Opitz trigonocephaly C syndrome (OTCS) is a multiple congenital anomaly syndrome characterized by trigonocephaly, mental retardation, a typical facial appearance, redundant skin, joint and limb abnormalities, and visceral anomalies. We describe a patient with the manifestations of OTCS who also had a de novo balanced reciprocal translocation t(3;18)(q13.13q12.1). His phenotype is a mild form with mild developmental delay and no severe visceral anomalies. Our findings suggest the possible existence of a new locus responsible for OTCS either on 3q13.13 or 18q12.1.