Hypocalcemic Seizure in a Girl with FOXG1-Gene–Related Encephalopathy

Objectives: The aim of this study is to present a case of hypocalcemia in a girl with FOXG1 gene-related encephalopathy, epilepsy, and severe vitamin D deficiency, and to differentiate the hypocalcemic tetanic seizures from the tonic seizures, both experienced by the patient. Methods: Case report. Results: We report an 11-year-old girl with “atypical” Rett syndrome due to a FOXG1 gene mutation with microcephaly, developmental delay, dyssomnia, and previously diagnosed drug resistant epilepsy with complex partial, tonic, myoclonic and generalized tonic-clonic seizures. She presented with multiple episodes of jerks affecting the extremities for the last 2 months, initially interpreted as epileptic seizures, and was admitted to the intensive care unit. Laboratory studies showed hypocalcemia, 1.3 mmol/L (ref 2.18-2.60), with ionized calcium of 0.75 mmol/L (ref 1.13-1.32). PTH was 511 pg/ml (ref 11-87), alkaline phosphatase was 1125 U/L (ref 42-406), and 1,25-dihydroxyvitamin D level was low at 5.5 pg/ml (ref. 7.61-55.5). Hand X-Ray revealed osteoporosis. EEG showed diffuse slowing. Therapy with intravenous calcium gluconate and oral vitamin D was initiated immediately. The condition improved and good seizure control was achieved. Conclusion: Vitamin D deficiency which may lead to severe hypocalcaemia is prevalent in girls with “atypical” Rett syndrome. Our clinical case highlights the importance of hypocalcemia as a triggering factor for tetanic spasms in such patients, which can be misinterpreted as epileptic seizures.
Keywords: hypocalcemia, Rett syndrome, seizures