Expanding the clinical phenotype and genetic spectrum of PURA-related neurodevelopmental disorders

Inherited PURA Pathogenic Variant Associated With a Mild Neurodevelopmental Disorder

Objectives

Purine-rich element-binding protein alpha (PURA) regulates gene expression and is ubiquitously expressed with an enrichment in neural tissues. Pathogenic variants in PURA cause the neurodevelopmental disorder PURA syndrome that has a variable phenotype but typically comprises moderate-to-severe global developmental delay, intellectual disability, early-onset hypotonia and hypothermia, epilepsy, feeding difficulties, movement disorders, and subtle facial dysmorphism. Speech is reportedly absent in most, but the specific linguistic phenotype is not well described.

Methods

We used genome sequencing to identify a pathogenic gene variant as part of a study of children ascertained for severe primary speech disorder in the absence of moderate or severe ID.

Results

The novel PURA c.296G>T (p.Arg99Leu) pathogenic missense variant segregated in the female proband and her affected mother. The proband had dysarthria; phonological disorder; and severe receptive and expressive language impairment, borderline intellect, attention difficulties, oropharyngeal dysmotility, and dysmorphic facial features. Her mother had dysarthria, moderate receptive language impairment, and borderline intellect. Both the proband and her mother completed mainstream schooling with classroom support.

Discussion

This is the first inherited PURA pathogenic germline variant in over 600 unrelated families documented on ClinVar or reported in the literature. PURA testing should be considered in families with primary speech disorder and borderline intellectual disability, given the specific genetic counseling implications.

Differences in manifestations of epilepsy and developmental delay in PURA syndrome and 5q31 microdeletions

PURA is mapped to chromosome 5q31 and plays a vital role in neuronal development and synapse formation. Here, we aim to explore PURA's impact on cognitive development and epilepsy phenotype by comparing patients with single nucleotide variants (SNPs) in the PURA gene (PURA-SNP patients) to those with 5q31 microdeletions including PURA (5q31del + PURA) and those with 5q31 microdeletions not including the PURA gene (5q31del-PURA). A systematic literature search was conducted in PubMed. Two separate searches were performed in order to find patients with PURA SNPs and 5q31 microdeletions. This review includes data from 191 patients collected from a total of 18 articles; 174 of the patients had PURA SNPs, 13 had 5q31 microdeletions involving the PURA gene, and 4 had 5q31 microdeletions without PURA gene implication. All patients exhibited hypotonia, feeding difficulties and dysmorphic features, however epilepsy was primarily present in patients with PURA syndrome, that is, groups PURA-SNP and 5q31del + PURA. Regarding the developmental milestones the 5q31del + PURA group stood out as being the most severe, while the 5q31del-PURA group showed a relatively mild phenotype. Our findings support the hypothesis of PURA being the key contributor of developmental delay and epilepsy among patients with PURA syndrome.

Movement Disorders in PURA Syndrome: A Video Case Series

Background

PURA syndrome is a rare genetic disorder characterized by neonatal hypotonia, neurodevelopmental delay, facial dysmorphism, epileptic seizures, complex movement disorders, among other features. Although many pathogenic variants have been reported, there is currently no clear genotype-phenotype association identified.

Cases

Four patients diagnosed with PURA syndrome, despite carrying different pathogenic variants, presented a similar mixed hyperkinetic movement disorder. The phenomenology presented a complex set of symptoms, including chorea, interspersed with dystonic and uncoordinated movements. All patients presented also hypotonia, nystagmus, feeding difficulties, craniofacial dysmorphisms. Hypersomnolence and breathing problems were common and observed in three patients, while seizures were found in three patients.

Conclusions

PURA syndrome may be considered in the differential diagnosis of infants with severe hypotonia, feeding difficulties and severe developmental delay with epileptic seizures, that start to develop a mixed hyperkinetic movement disorder. These complex movements may be an important clue for the diagnosis of this rare disorder.

Neuromuscular and Neuromuscular Junction Manifestations of the PURA-NDD: A Systematic Review of the Reported Symptoms and Potential Treatment Options

PURA-related neurodevelopmental disorders (PURA-NDDs) are a rare genetic disease caused by pathogenic autosomal dominant variants in the PURA gene or a deletion encompassing the PURA gene. PURA-NDD is clinically characterized by neurodevelopmental delay, learning disability, neonatal hypotonia, feeding difficulties, abnormal movements, and epilepsy. It is generally considered to be central nervous system disorders, with generalized weakness, associated hypotonia, cognitive and development deficits in early development, and seizures in late stages. Although it is classified predominantly as a central nervous syndrome disorder, some phenotypic features, such as myopathic facies, respiratory insufficiency of muscle origin, and myopathic features on muscle biopsy and electrodiagnostic evaluation, point to a peripheral (neuromuscular) source of weakness. Patients with PURA-NDD have been increasingly identified in exome-sequenced cohorts of patients with neuromuscular- and congenital myasthenic syndrome-like phenotypes. Recently, fluctuating weakness noted in a PURA-NDD patient, accompanied by repetitive nerve stimulation abnormalities, suggested the disease to be a channelopathy and, more specifically, a neuromuscular junction disorder. Treatment with pyridostigmine or salbutamol led to clinical improvement of neuromuscular function in two reported cases. The goal of this systematic retrospective review is to highlight the motor symptoms of PURA-NDD, to further describe the neuromuscular phenotype, and to emphasize the role of potential treatment opportunities of the neuromuscular phenotype in the setting of the potential role of PURA protein in the neuromuscular junction and the muscles.

A 25 Mainland Chinese cohort of patients with PURA-related neurodevelopmental disorders: clinical delineation and genotype-phenotype correlations

PURA-related neurodevelopmental disorders (PURA-NDDs) include 5q31.3 microdeletion syndrome and PURA syndrome. PURA has been proposed as a candidate gene responsible for 5q31.3 microdeletion syndrome. Phenotype comparisons between patients with PURA mutations and 5q31.3 microdeletions encompassing more than PURA gene are lacking. A total of 25 previously undescribed Mainland China patients were evaluated. Clinical data were obtained from medical record review and standardized medical history questionnaire. Clinical profile and genetic spectrum of the patients with PURA syndrome and genotype-phenotype correlations between PURA mutations group and 5q31.3 microdeletions group were analyzed. Our identified seventeen de nove PURA variants were novel, and two recurrent frameshift variants, c.697_699del (p.F233del) and c.159dup (p.L54Afs*147) were detected in the four independent pedigrees. One patient with 5q31.3 microdeletion further supported the shortest overlapping region only contains PURA and IGIP gene. Developmental delay/intellectual disability, neonatal hypotonia, neonatal feeding difficulties, hypersomnolence and dysmorphic features were prominent clinical features in PURA syndrome. There was no significant difference between two groups in incidence of neonatal problems, developmental delay and common medical comorbidities. We observed a higher frequency of abnormal brain MRI and specific facial dysmorphism in 5q31.3 microdeletion group. This is the first work describing a largest cohort of Mainland China patients broaden the clinical and molecular spectrum of PURA-NDDs. Our findings not only demonstrated that PURA haploinsufficiency was a major contributor to the important phenotypes of 5q31.3 microdeletion, but also implied that additional genes still played a role in the 5q31.3 microdeletion.