Beyond Primary Epilepsy: Fahr's Syndrome Secondary to Congenital Parathyroid Agenesis Presenting With Generalised Seizures in a Young Adult

Symmetrical, bilateral intracranial calcifications, commonly involving the basal ganglia, constitute the characteristic features of Fahr's syndrome, which is an uncommon neurometabolic condition.Its incidence in conjunction with congenital parathyroid agenesis, however, has rarely been reported.The present case emphasises how crucial it is to identify the metabolic origins of intracranial calcification and differentiate Fahr's syndrome from primary familial brain calcification to prevent repeated neurological consequences through adequate therapy.A 26-year-old man with congenital absence of the parathyroid gland presented to the emergency department after a 10-minute generalised tonic-clonic seizure, preceded by twitching of the perioral muscles.Examination revealed continuous perioral twitching, drowsiness in the postictal state and a positive Chvostek sign.Although the serum 25-hydroxyvitamin D (25-OH vitamin D) level remained within the normal range (88 nmol/L), laboratory tests revealed severe hypocalcaemia (1.44 mmol/L), hyperphosphatemia (1.95 mmol/L) and undetectable parathyroid hormone (<0.1 pmol/L), supporting hypoparathyroidism as the underlying cause of his symptoms.Non-contrast computed tomography (CT) of the head demonstrated typical bilateral symmetric basal ganglia calcifications, consistent with Fahr's syndrome, and an electrocardiogram (ECG) revealed QT interval prolongation.Intravenous calcium, oral calcium supplements, and alfacalcidol were used to treat the patient; this led to the correction of hypocalcaemia, full resolution of neuromuscular symptoms and no more seizures while the patient was in the hospital.This case demonstrates the rare correlation between Fahr's syndrome and congenital parathyroid agenesis that manifests in early adulthood.It highlights how crucial it is to take reversible metabolic factors into account when young adults exhibit new-onset seizures.Adequate vitamin D stores alone cannot maintain calcium homeostasis in individuals with congenital hypoparathyroidism, as evidenced by the significant hypocalcaemia that developed despite normal vitamin D status due to lacking parathyroid hormone.