Implications of Genetic Variants in Cerebral Palsy—Reply

Abstract

COMMENT & RESPONSEIn Reply We appreciate the opportunity to respond to 2 letters regarding our systematic review and meta-analysis, 1 which found that the diagnostic yield of exome sequencing (ES) was 31.1% among individuals with cerebral palsy (CP), similar to the yield in other neurodevelopmental disorders (NDDs) for which ES is recommended as standard of care. Our study provides evidence supporting the inclusion of CP among the NDDs for which clinical ES is currently recommended as standard of care.Zhang and Li suggest that we should be cautious with our recommendation since they believe that some individuals from 2 of the cohorts included in our study were misdiagnosed with CP. Our systematic review and meta-analysis relied on data reported by multiple studies from various populations of individuals with a clinical diagnosis of CP. While it is possible that some cases of CP may have been misdiagnosed, these are realworld cohorts of individuals with working clinical diagnoses of CP who have undergone ES.We respectfully disagree that misdiagnosis of CP is proven by any genetic finding. CP is a clinical diagnosis, not one made by any laboratory test or imaging study. 2 Pleiotropy and variable expressivity are the rule, rather than the exception, when it comes to genetic etiologies of NDDs. As such, pathogenic variants in genes, such as SCN1A or KCNQ2, are often associated with epilepsy, intellectual disability, autism, and other phenotypes, including CP. In fact, spastic quadriplegia is common among children with KCNQ2-related disorders. 3 Having a primary epilepsy phenotype does not negate the diagnosis of CP if the clinical criteria are met.A different issue was raised with pathogenic variants in genes known to be associated with hereditary spastic paraplegia (HSP), since the primary known presentation is a motor phenotype that is ultimately progressive and therefore not consistent with a clinical diagnosis of CP. Individuals with pathogenic variants in some HSP-associated genes, such as SPAST, may have a phenotype that appears to be consistent CP in early childhood, thus warranting inclusion in clinical CP cohorts. However, finding a genetic variant that causes a progressive phenotype, such as HSP, should prompt clinical reassessment and reappraisal of the appropriateness of the CP diagnosis. 2 In this specific case, if there is evidence of clinical progression, the diagnosis of CP should be changed. However, it is also possible that cases of nonprogressive motor phenotypes consistent with CP will be identified with variants in some of these genes in the future, and the diagnosis of CP should continue to be based on the clinical findings.We also appreciate the supportive comments by Evans et al, who provided insights into the content and implications of our study and, along with the authors of the accompanying editorial, agree that exome sequencing should be offered to all individuals with CP. 4 As discussed in our article, there are numerous benefits of finding a genetic cause in individuals with CP.