Early ultrasonographic changes in Fowler syndrome features and review of the literature

Expanding the clinical spectrum of Fowler syndrome: Three siblings with survival into adulthood and systematic review of the literature

Proliferative vasculopathy and hydranencephaly-hydrocephaly syndrome (PVHH, OMIM 225790), also known as Fowler syndrome, is a rare autosomal recessive disorder of brain angiogenesis. PVHH has long been considered to be prenatally lethal. We evaluated the phenotypes of the first three siblings with survival into adulthood, performed a systematic review of the Fowler syndrome literature and delineated genotype-phenotype correlations using a scoring system to rate the severity of the disease. Thirty articles were included, describing 69 individual patients. To date, including our clinical reports, 72 patients have been described with Fowler syndrome. Only 6/72 (8%) survived beyond birth. Although our three patients carry the same mutations (c.327T>A-p.Asn109Lys and c.887C>T-p.Ser296Leu) in FLVCR2, only two of them presented with the same cerebral features, ventriculomegaly and cerebral calcifications, as affected fetuses. The third sibling has a surprisingly milder clinical and radiological phenotype, suggesting intrafamilial variability. Although no clear phenotype-genotype correlation exists, some variants appear to be associated with a less severe phenotype compatible with life. As such, it is important to consider Fowler syndrome in patients with gross ventriculomegaly, cortical malformations and/or cerebral calcifications on brain imaging.

A rare variation of hydranencephaly: case report

Hydranencephaly is a rare congenital abnormality characterized by the absence and replacement of the cerebral hemispheres with cerebrospinal fluid. Here, we present an ultrasonographic diagnosis of a case of a rare variant of fetal hydranencephaly at 38 weeks of gestation. Obstetric sonography revealed the absence of the cerebral cortex, thalami and basal ganglia with a disrupted falx and preserved posterior fossa structures. This is the first reported case of hydranencephaly with the absence of the thalami and basal ganglia, which was diagnosed prenatally. The diagnosis was confirmed with postnatal computed tomography. The early prenatal diagnosis allowed for prompt obstetric attention at a tertiary care hospital which had specialized pediatric facilities including prenatal counseling and support.

Unexpected allelic heterogeneity and spectrum of mutations in Fowler syndrome revealed by next-generation exome sequencing

Protein coding genes constitute approximately 1% of the human genome but harbor 85% of the mutations with large effects on disease-related traits. Therefore, efficient strategies for selectively sequencing complete coding regions (i.e., "whole exome") have the potential to contribute our understanding of human diseases. We used a method for whole-exome sequencing coupling Agilent whole-exome capture to the Illumina DNA-sequencing platform, and investigated two unrelated fetuses from nonconsanguineous families with Fowler Syndrome (FS), a stereotyped phenotype lethal disease. We report novel germline mutations in feline leukemia virus subgroup C cellular-receptor-family member 2, FLVCR2, which has recently been shown to cause FS. Using this technology, we identified three types of genetic abnormalities: point-mutations, insertions-deletions, and intronic splice-site changes (first pathogenic report using this technology), in the fetuses who both were compound heterozygotes for the disease. Although revealing a high level of allelic heterogeneity and mutational spectrum in FS, this study further illustrates the successful application of whole-exome sequencing to uncover genetic defects in rare Mendelian disorders. Of importance, we show that we can identify genes underlying rare, monogenic and recessive diseases using a limited number of patients (n=2), in the absence of shared genetic heritage and in the presence of allelic heterogeneity.

Mutations in FLVCR2 are associated with proliferative vasculopathy and hydranencephaly-hydrocephaly syndrome (Fowler syndrome)

Proliferative vasculopathy and hydranencephaly-hydrocephaly syndrome (PVHH), also known as Fowler syndrome, is an autosomal-recessively inherited prenatal lethal disorder characterized by hydranencephaly; brain stem, basal ganglia, and spinal cord diffuse clastic ischemic lesions with calcifications; glomeruloid vasculopathy of the central nervous system and retinal vessels; and a fetal akinesia deformation sequence (FADS) with muscular neurogenic atrophy. To identify the molecular basis for Fowler syndrome, we performed autozygosity mapping studies in three consanguineous families. The results of SNP microarrays and microsatellite marker genotyping demonstrated linkage to chromosome 14q24.3. Direct sequencing of candidate genes within the target interval revealed five different germline mutations in FLVCR2 in five families with Fowler syndrome. FLVCR2 encodes a transmembrane transporter of the major facilitator superfamily (MFS) hypothesized to be involved in regulation of growth, calcium exchange, and homeostasis. This is the first gene to be associated with Fowler syndrome, and this finding provides a basis for further studies to elucidate the pathogenetic mechanisms and phenotypic spectrum of associated disorders.

Fowler syndrome presenting as a Dandy-Walker malformation: a second case report

Fowler syndrome, also known as proliferative vasculopathy and hydrocephaly-hydranencephaly, is a lethal condition characterized by hydrocephalus associated with progressive destruction of central nervous system tissue as a result of an unusual and characteristic proliferative vasculopathy. The occurrence of Fowler syndrome in consanguineous families and recurrence in both sexes are suggestive of an autosomal recessive transmission. We present the second case of Fowler syndrome presenting as a Dandy-Walker malformation, in a consanguineous family.