Severe microcephaly

Gene: FLVCR1

Green List (high evidence)

Comment on list classification: Promoting this gene to amber with a recommendation for green rating following GMS review.

Created: 14 Jul 2025, 8:15 p.m. | Last Modified: 14 Jul 2025, 8:15 p.m.

Panel Version: 8.7

Associated with Neurodevelopmental disorder with microcephaly, absent speech, and hypotonia, OMIM:621060.

Variants in this gene have been previously associated with a progressive Retinopathy-sensory neuropathy syndrome, OMIM:609033

PMID: 39306721 - Calame et al 2025 report 27 individuals from 20 families with homozygous/compound het variants in this gene (mainly missense, but also nonsense, frameshift and splice variants). 2 families from S Asia share the same variant and haplotype so could be a founder variant in the region.

13/27 individual had profound ID/DD. 3 were stillborn, and 10 others died before the age of 5, including one in the neonatal period. Severe microcephaly (Z score below -3.0) was observed in 12/27 individuals. Epilepsy was reported in 12 individuals, hypotonia in 17, spasticity in 9 (from 6 families), reduced brain volume in 19 , craniofacial malformations in 4 (those that were still born or died in neonatal period), and limb malformations in 7. An eye phenotype (Cortical visual impairment, Optic disk atrophy or Retinitis pigmentosa) was observed in 15 individuals.

All pathogenic FLVCR1 variants were rare and absent in the homozygous state in gnomAD v2.1.13. Functional studies show that pathogenic FLVCR1 missense variants primarily lie within transmembrane domains and reduce choline and ethanolamine transport activity compared with wild-type FLVCR1.

There are more than 3 cases reported with plausible disease causing variants in more than 3 cases for the intellectual disability, epilepsy, severe microcephaly, limb disorders, fetal anomalies and childhood onset hereditary spastic paraplegia panels. The gene will also be included in the Hypotonic infant superpanel through the inclusion on the Intellectual disability panel.
Sources: Literature

Created: 14 Jul 2025, 8:14 p.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Neurodevelopmental disorder with microcephaly, absent speech, and hypotonia, OMIM:621060; neurodevelopmental disorder with microcephaly, absent speech, and hypotonia, MONDO:0976126

Publications

• 39306721