Hydrocephalus, Congenital, 1

A number sign (#) is used with this entry because of evidence that congenital hydrocephalus-1 (HYC1) is caused by homozygous mutation in the CCDC88C gene (611204) on chromosome 14q32.

Description

Congenital hydrocephalus-1 is characterized by onset in utero of enlarged ventricles due to a disturbance of cerebrospinal fluid accumulation. Affected individuals may have neurologic impairment (summary by Drielsma et al., 2012).

Hydrocephalus can also be caused by Arnold-Chiari malformation, atresia of foramen of Magendie, stenosis of aqueduct of Sylvius (307000), toxoplasmosis, hydranencephaly, etc. Furthermore, it develops in infancy or childhood in achondroplasia (100800) and in Hurler disease (607014).

Genetic Heterogeneity of Congenital Hydrocephalus

See also HYC2 (615219), caused by mutation in the MPDZ gene (603785) on chromosome 9p23, and HYC3 (617967), caused by mutation in the WDR81 gene (614218) on chromosome 17p13.

An X-linked form of congenital hydrocephalus (HSAS, HYCX; 307000) is caused by mutation in the L1CAM gene on (308840) on chromosome Xq28.

Clinical Features

Ekici et al. (2010) reported a girl, born of consanguineous parents of Algerian origin, with congenital nonsyndromic hydrocephalus. Fetal ultrasound at 25 weeks' gestation showed enlarged ventricles. Brain MRI at age 3 days showed dilatation of the lateral ventricles with normal third and fourth ventricles. A diverticulum-like pouch extended from the medial-posterior aspect of the left lateral ventricle into the interhemispheric space, extending through the tentorium into the infratentorial space, leading to mild compression of the upper cerebellar vermis. The posterior fossa was markedly enlarged with supra- and retrocerebellar fluid accumulation. Communication between the fourth ventricle and the cisterna magna was normal. The child had seizures, but showed no other malformations, dysmorphism, or neurologic anomalies. At age 3 years, she showed normal psychomotor development. An earlier pregnancy of these parents had been terminated due to ventricular enlargement detected on prenatal ultrasound.

Drielsma et al. (2012) reported 2 unrelated consanguineous families with autosomal recessive nonsyndromic hydrocephalus. In 1 Ashkenazi Jewish family, 4 sibs had congenital hydrocephalus and seizures. The head circumferences at birth ranged from 39.5 to 49 cm, and all were delivered by cesarean section. Two had midline cystic structures and 1 had an extra-axial parietal cyst, but none had an enlarged fourth ventricle. One child had biparietal polymicrogyria. All were developmentally delayed, with moderate to severe mental retardation and motor impairment; one 18-year-old was severely affected and only able to sit. In the second family, a first-cousin couple of Palestinian origin underwent 5 terminations of pregnancy following the diagnosis of marked ventricular dilatation at mid-gestation. The couple also had a twin miscarriage at 10 weeks' gestation.

Wallis et al. (2018) reported 5 patients with HYC1 from 2 consanguineous families (one from Saudi Arabia and one form Morocco) and reviewed clinical findings in previously reported patients. Most patients had evidence of proximal obstruction at the level of the aqueduct and absence of significant malformations outside the brain. Two patients, including 1 reported by Wallis et al. (2018), met their early childhood milestones. Four of 6 individuals with evidence of developmental delay came from a single family reported by Drielsma et al. (2012); these patients had a focal seizure disorder and required at least 1 shunt revision, and 1 patient had biparietal polymicrogyria. Wallis et al. (2018) suggested that normal developmental outcomes were more likely in patients without additional brain malformations who received a shunt in the first few weeks of life, did not require multiple surgical revisions, and had a more distal truncating variant of the CCD88C gene.

Inheritance

Schockaert and Janssens (1952) observed 4 sibs, including a female, with hydrocephalus. Abdul-Karim et al. (1964) reported 2 instances of consanguineous unions, each of which resulted in 3 affected sibs. I have knowledge of an Amish family in which 1 female and 2 male sibs have hydrocephalus. The family studied by Mehne (1961) was non-Amish, living in Indiana. Borle (1953) reviewed the instances of familial hydrocephalus and Gellman (1959) reviewed those of hydrocephalus in twins.

In a study of hydrocephalus in a 20-year period in Victoria, Australia, Halliday et al. (1986) observed possible autosomal recessive inheritance in 2 families out of 91.

In a report on X-linked hydrocephalus (307000), Varadi et al. (1987) stated that they had seen 6 families with isolated hydrocephalus of which 4 appeared to be autosomal recessive and 2 X-linked recessive. Varadi et al. (1988) reported on 261 prospectively ascertained pregnancies studied to determine the recurrence risk of congenital hydrocephalus. Their results suggested that the recurrence risk is about 4%, and that 'apart from the X-linked recessive cases, ventriculomegaly is mostly multifactorially determined.' Teebi and Naguib (1988) observed nonsyndromic hydrocephalus in 4 sibs of a consanguineous Arab family in Kuwait. The Arnold-Chiari malformation was confirmed in 1 by autopsy and was suspected in the other 3. Chow et al. (1990) reported a brother and sister who presented in the neonatal period with hydrocephalus due to obstruction of the third ventricle.

Zlotogora et al. (1994) suggested that an autosomal recessive form of hydrocephalus with prenatal onset is particularly frequent among Palestinian Arabs. Among 14 families in which more than 1 child was diagnosed with hydrocephalus of prenatal onset, in 7, only males were affected: in 2, X-linked hydrocephalus was diagnosed, while X-linked inheritance was suspected in 3 other families. These 5 families were of Jewish origin. In all 8 families of Arab origin, the parents of the affected children were consanguineous.

Mapping

By homozygosity mapping of a large consanguineous family of Algerian origin with nonsyndromic hydrocephalus, Ekici et al. (2010) found linkage to a 3.37-Mb region on chromosome 14 between SNPs rs41463644 and rs7148382 (maximum lod score close to 3).

Molecular Genetics

In a girl, born of consanguineous parents, with nonsyndromic hydrocephalus, Ekici et al. (2010) identified a homozygous splice site mutation in the CCDC88C gene (611204.0001), resulting in premature termination. An affected fetus, a sib of the girl, was also found to carry this homozygous mutation. The mutation was found by homozygosity mapping followed by candidate gene sequencing. Protein and gene expression profiling indicated disturbed regulation of the WNT (see, e.g., WNT3A, 606359) signaling pathway.

In affected members of 2 unrelated families with congenital hydrocephalus, Drielsma et al. (2012) identified 2 different homozygous mutations in the CCDC88C gene (611204.0002-611204.0003).

In 2 consanguineous families with congenital hydrocephalus, Wallis et al. (2018) identified homozygous mutations in the CCDC88C gene (see, e.g., 611204.0005). The mutations, which were identified by next-generation sequencing and confirmed by Sanger sequencing, segregated with the disorder in the families.

Animal Model

The H-Tx rat strain has prenatal hydrocephalus associated with obstruction of the cerebral aqueduct (Jones and Bucknall, 1988). Linkage studies by Jones et al. (2001) showed that hydrocephalus in the rat is associated with several different chromosomes.