Clinical Features of Okur-Chung Neurodevelopmental Syndrome: Case Report and Literature Review

Patient with a heterozygous pathogenic variant in CSNK2A1 gene: A new case to update the Okur-Chung neurodevelopmental syndrome

The autosomal dominant Okur-Chung neurodevelopmental syndrome (OCNDS: OMIM #617062) is a rare neurodevelopmental disorder first described in 2016. Features include developmental delay (DD), intellectual disability (ID), behavioral problems, hypotonia, language deficits, congenital heart abnormalities, and non-specific dysmorphic facial features. OCNDS is caused by heterozygous pathogenic variants in CSNK2A1 (OMIM *115440; NM_177559.3). To date, 160 patients have been diagnosed worldwide. The number will likely increase due to the growing use of exome sequencing (ES) and genome sequencing (GS). Here, we describe a novel OCNDS patient carrying a CSNK2A1 variant (NM_177559.3:c.140G>A; NP_808227.1:p.Arg47Gln). Phenotypically, he presented with DD, ID, generalized hypotonia, speech delay, short stature, microcephaly, and dysmorphic features such as low-set ears, hypertelorism, thin upper lip, and a round face. The patient showed several signs not yet described that may extend the phenotypic spectrum of OCNDS. These include prenatal bilateral clubfeet, exotropia, and peg lateral incisors. However, unlike the majority of descriptions, he did not present sleep disturbance, seizures or gait difficulties. A literature review shows phenotypic heterogeneity for OCNDS, whether these patients have the same variant or not. This case report is an opportunity to refine the phenotype of this syndrome and raise the question of the genotype-phenotype correlation.

Okur-Chung neurodevelopmental syndrome: Implications for phenotype and genotype expansion

BACKGROUND

Okur-Chung neurodevelopmental syndrome (OCNDS) is a rare autosomal dominant disorder caused by pathogenic variants in CSNK2A1. It is characterized by intellectual disability, developmental delay, and multisystemic abnormalities.

METHODS

We performed the whole-exome sequencing for a patient in a Chinese family. The co-segregation study using the Sanger sequencing method was performed among family members. Reverse transcription and quantitative real-time polymerase chain reaction were carried out using total RNA from blood samples of the proband and wild-type control subjects. A review of patients with OCNDS harboring CSNK2A1 pathogenic variants was conducted through a comprehensive search of the PubMed database.

RESULTS

We identified a novel CSNK2A1 frameshift variant p.Tyr323Leufs*16 in a Chinese family. The proband, a 31-year-old female, presented with abnormal eating habits, recurrent seizures, language impairment, and intellectual disability. Her mother exhibited postnatal hernias, splenomegaly, and a predisposition to infections, but showed no significant developmental impairments or intellectual disability. Genetic studies revealed the presence of this variant in CSNK2A1 in both the proband and her mother. Transcription analysis revealed this variant may lead to nonsense-mediated mRNA decay, suggesting haploinsufficiency as a potential disease mechanism. We reviewed 47 previously reported OCNDS cases and discovered that individuals carrying CSNK2A1 null variants may exhibit a diminished frequency of symptoms linked to language deficits, dysmorphic facial features, or intellectual disability, consequently presenting an overall milder phenotype when compared to those with missense variants.

CONCLUSION

We report a novel frameshift variant, p.Tyr323Leufs*16, in an OCNDS family with a generally mild phenotype. This study may broaden the spectrum of clinical presentations associated with OCNDS and contribute novel insights into the genotype-phenotype correlation of this condition.

Inherited CSNK2A1 variants in families with Okur-Chung neurodevelopmental syndrome

Pedigree showing the autosomal dominant inheritance pattern of CSNK21 variants in families presenting with OCNDS. (A) Maternal inheritance to two daughters in Family 1, (B) Paternal inheritance to a daughter in Family 2, and (C) Maternal inheritance to two sons in Family 3.

Genotypic and phenotypic spectrum of Myofibrillar Myopathy 7 as a result of Kyphoscoliosis Peptidase deficiency: The first description of a missense mutation in KY and literature review

KY is located on chromosome 3 and encodes a transglutaminase-like protein in the skeletal muscles, namely Kyphoscoliosis Peptidase. KY is primarily involved in the formation and stabilization of neuromuscular intersections making it essential for the development of the musculoskeletal system. Mutations in KY cause Myofibrillar Myopathy-7 (MFM-7) and Hereditary Spastic Paraplegia (HSP). MFM-7 is an early onset muscle disorder with an autosomal recessive inheritance marked by progressive muscle weakness and joint contractures. Herein, we describe an Iranian family with MFM-7 caused by a homozygous novel variant in KY. We identified a homozygous variant (NM_178554.6:c.1247T > A, p. Ile416Asn) in KY in two patients born to consanguineous parents and the same heterozygous mutation in their parent by Whole-Exome Sequencing. The patients manifest muscle weakness, muscle atrophy, mobility restriction, and hyporeflexia. Lastly, we reviewed the phenotype and corresponding genotype of the previously reported cases with pathogenic variants in KY.