WDR62 primary microcephaly

Inspired by a patient

Verloes A, Ruaud L, Drunat S, Passemard S. WDR62 Primary Microcephaly. 2022 Feb 17. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2024. PMID: 35188728.

Excerpt

Clinical characteristics: In WDR62 primary microcephaly (WDR62-MCPH), microcephaly (occipitofrontal circumference [OFC] ≥2 standard deviations below the mean) is usually present at birth, but in some instances becomes evident later in the first year of life. Growth is otherwise normal. Except for brain malformations in most affected individuals, no other congenital malformations are observed. Central nervous system involvement can include delayed motor development, mild-to-severe intellectual disability (ID), behavior problems, epilepsy, spasticity, and ataxia.

Diagnosis/testing: The diagnosis of WDR62-MCPH is established in a proband with suggestive clinical findings and biallelic pathogenic variants in WDR62 identified by molecular genetic testing.

Management: Treatment of manifestations: Treatment is symptomatic. Care by a multidisciplinary team (often including a pediatric neurologist, developmental pediatrician, speech-language pathologist, occupational and physical therapist, medical geneticist, and social worker) is recommended.

Surveillance: Follow up at each visit to assess: neurologic manifestations and response to medications for those with seizures; developmental progress and educational needs; speech-language development; behavior; physical therapy / occupational therapy needs; and social support.

Genetic counseling: WDR62-MCPH is inherited in an autosomal recessive manner. If both parents are known to be heterozygous for a WDR62 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Once the WDR62 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives, prenatal testing, and preimplantation genetic testing are possible.

Ruaud L, Drunat S, Elmaleh-Bergès M, Ernault A, Guilmin Crepon S; MCPH Consortium; El Ghouzzi V, Auvin S, Verloes A, Passemard S. Neurological outcome in WDR62 primary microcephaly. Dev Med Child Neurol. 2022 Apr;64(4):509-517. doi: 10.1111/dmcn.15060. Epub 2021 Sep 25. PMID: 35726608.

Abstract

Aim: To characterize the cortical structure, developmental, and cognitive profiles of patients with WD repeat domain 62 (WDR62)-related primary microcephaly.

Method: In this observational study, we describe the developmental, neurological, cognitive, and brain imaging characteristics of 17 patients (six males, 11 females; mean age 12y 3mo standard deviation [SD] 5y 8mo, range 5y-24y 6mo) and identify 14 new variants of WDR62. We similarly analyse the phenotypes and genotypes of the 59 previously reported families.

Results: Brain malformations, including pachygyria, neuronal heterotopia, schizencephaly, and microlissencephaly, were present in 11 out of 15 patients. The mean full-scale IQ of the 11 assessed patients was 51.8 (standard deviation [SD] 12.6, range 40-70). Intellectual disability was severe in four patients, moderate in four, and mild in three. Scores on the Vineland Adaptive Behavior Scales obtained from 10 patients were low for communication and motor skills (mean 38.29, SD 7.74, and 37.71, SD 5.74 respectively). The socialization score was higher (mean 47.14, SD 12.39). We found a significant difference between scores for communication and daily living skills (mean 54.43, SD 11.6; p=0.001, one-way analysis of variance). One patient displayed progressive ataxia.

Interpretation: WDR62-related cognitive consequences may be less severe than expected because 3 out of 11 of the assessed patients had only mild intellectual disability and relatively preserved abilities of autonomy in daily life. We identified progressive ataxia in the second decade of life in one patient, which should encourage clinicians to follow up patients in the long term.

Zombor M, Kalmár T, Nagy N, Berényi M, Telcs B, Maróti Z, Brandau O, Sztriha L. A novel WDR62 missense mutation in microcephaly with abnormal cortical architecture and review of the literature. J Appl Genet. 2019 May;60(2):151-162. doi: 10.1007/s13353-019-00486-y. Epub 2019 Feb 1. PMID: 30706430.

Abstract

Autosomal recessive primary microcephaly (MCPH) is a group of rare neurodevelopmental diseases with severe microcephaly at birth. One type of the disorder, MCPH2, is caused by biallelic mutations in the WDR62 gene, which encodes the WD repeat-containing protein 62. Patients with WDR62 mutation may have a wide range of malformations of cortical development in addition to congenital microcephaly. We describe two patients, a boy and a girl, with severe congenital microcephaly, global developmental delay, epilepsy, and failure to thrive. MRI showed hemispherical asymmetry, diffuse pachygyria, thick gray matter, indistinct gray-white matter junction, and corpus callosum and white matter hypoplasia. Whole exome sequencing revealed the same novel homozygous missense mutation, c.668T>C, p.Phe223Ser in exon 6 of the WDR62 gene. The healthy parents were heterozygous for this mutation. The mutation affects a highly conserved region in one of the WD repeats of the WDR62 protein. Haplotype analysis showed genetic relatedness between the families of the patients. Our findings expand the spectrum of mutations randomly distributed in the WDR62 gene. A review is also provided of the brain malformations described in WDR62 mutations in association with congenital microcephaly.