Fahr's syndrome secondary to chronic hypoparathyroidism in a patient residing at high altitude

Abstract

Introduction: Fahr's syndrome refers to secondary forms of bilateral, symmetrical cerebral calcification, with hypoparathyroidism being the most common endocrine cause. Unlike primary familial cerebral calcification, the underlying disorder is correctable, giving the etiological diagnosis direct therapeutic significance. Case report: A 61-year-old patient with a history of partial thyroidectomy and hypoparathyroidism (present for 25 years but managed without specialized follow-up) and a prior diagnosis of generalized epilepsy, chronic cor pulmonale, and recent pulmonary thromboembolism. The patient was admitted due to an acute exacerbation of chronic respiratory failure, presenting with a positive Trousseau sign, a QT interval of 609 ms, hypomagnesemia, hypokalemia, and metabolic alkalosis. PTH levels were < 3 pg/mL, and ionized calcium dropped to 0.54 mmol/L. A cranial CT scan revealed bilateral, symmetrical calcifications in the basal ganglia, dentate nuclei, frontoparietal white matter, and cerebellar hemispheres. Intravenous and oral calcium and magnesium replacement, combined with calcitriol and levothyroxine dosage adjustment, resolved the tetany and allowed for hospital discharge. Conclusions: Fahr's syndrome should be suspected in patients with long-standing hypoparathyroidism who present with neurological manifestations; a non-contrast CT scan is sufficient to document the condition. In the event of seizures in this context, hypocalcemia must be ruled out before maintaining a diagnosis of epilepsy. Direct measurement of ionized calcium, monitoring of phosphorus and magnesium levels, spacing out calcium and levothyroxine intake, and interpreting blood gas analysis with altitude adjustment are specific measures that alter clinical management.