Severe microcephaly

Gene: WARS

Green List (high evidence)

Comment on list classification: Promoting to amber with a recommendation for green rating following GMS review as there are 4 families with progressive microcephaly in the severe range.

Created: 9 Jul 2025, 9:59 p.m. | Last Modified: 9 Jul 2025, 10:03 p.m.

Panel Version: 8.5

Associated with Neurodevelopmental disorder with microcephaly and speech delay, with or without brain abnormalities OMIM:620317 (AR). Also associated with Neuronopathy, distal hereditary motor, autosomal dominant 9, OMIM:617721 (AD).

5 families reported with biallelic variants in WARS1 and phenotype of intellectual disability and progressive severe microcephaly in 4 families. Variable other phenotypes were also present such as hearing loss, skeletal and brain abnormalities and seizures.

PMID: 34585293 - Okamoto et al 2022 - 4 year old female Japanese proband with compound het variants in WARS1 (p.Arg448Trp and p.Ala333Thr). Parents were heterozygous. Variants are rare. She presented with hypotonia, developmental delay, delayed myelination in the cerebral white matter. She had a seizure age 2. Severe intellectual disability at age 4, did not walk independently. Head circumference was -0.4 SD at birth and -3.4 SD by age 4.

PMID: 35815345 - Lin et al 2022 - 3 probands from 2 consanguineous Pakistani families. In family 1, one proband at age 20 had developmental delay, mild ID, mild microcephaly, mild sensorineural hearing loss. The second proband at age 16 had severe delayed developmental milestones/intellectual disability, hypotonia, severe microcephaly (-7.8 SD), severe hearing impairment and skeletal abnormalities of the legs. In family 2, the 5 year male had global developmental delay, complex partial epilepsy, a history of central adrenal insufficiency, cortical blindness, and multiple brain abnormalities. He has a history of seizures. A homozygous, rare, start loss variant (c.1A>G, p.Met1?) in exon 2 of WARS1 was identified in family 1 with parents as carriers. A homozygous c.1255G>A, p.(Asp419Asn) variant was identified in WARS1 in family 2, with parents as carriers. This variant is present in population databases with a MAF ~ 0.003 but not in the homozygous state. Zebrafish wars1 knockout displayed microcephaly, hearing loss, and musculoskeletal abnormalities, and the homozygous animals do not survive past Day 10

PMID: 35790048 - Bögershausen et al 2022 - 4 individuals from 2 families all with the same missense variant in WARS1 (c.397C>T, p.(R133C)). All 4 had progressive microcephaly with OFC at (-4.2, -4.3, -3.8 and −3.5) at assessment at ages 5, 13, 8 and 7 years. the proband from family 1 had mild ID, the three from family 2 had severe ID and two from family 2 had hypotonia. No seizures or hearing loss was reported. The WARS1 variant negatively impacts protein abundance and is unable to rescue the phenotype of a CRISPR/Cas9 wars1 knockout zebrafish model.

Created: 9 Jul 2025, 6:01 p.m. | Last Modified: 9 Jul 2025, 9:58 p.m.

Panel Version: 9.33

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Neurodevelopmental disorder with microcephaly and speech delay, with or without brain abnormalities, OMIM:620317; neurodevelopmental disorder with microcephaly and speech delay, with or without brain abnormalities, MONDO:0957218

Publications

• 34585293
• 35790048
• 35815345