Specific Cognitive Changes due to Hippocalcin Alterations? A Novel Familial Homozygous Hippocalcin Variant Associated with Inherited Dystonia and Altered Cognition.

BACKGROUND: Recent research suggested an hippocalcin (HPCA)-related form of DYT2-like autosomal recessive dystonia. Two reports highlight a broad spectrum of the clinical phenotype. Here, we describe a novel HPCA gene variant in a pediatric patient and two affected relatives.

METHODS: Whole exome sequencing was applied after a thorough clinical and neurological examination of the index patient and her family members. Results of neuropsychological testing were analyzed.

RESULTS: Whole exome sequencing revealed a novel homozygous missense variant in the HPCA gene [c.182C>T p.(Ala61Val)] in our pediatric patient and the two affected family members. Clinically, the cases presented with dystonia, dysarthria, and jerky movements. We observed a particular cognitive profile with executive dysfunctions in our patient, which corresponds to the cognitive deficits that have been observed in the patients previously described.

CONCLUSION: We present a novel genetic variant of the HPCA gene associated with autosomal recessive dystonia in a child with childhood-onset dystonia supporting its clinical features. Furthermore, we propose specific HPCA-related cognitive changes in homozygous carriers, underlining the importance of undertaking a systematic assessment of cognition in HPCA-related dystonia.