Idiopathic hypoparathyroidism and systemic sclerosis: An association likely missed

Hypoparathyroidism in systemic sclerosis is extremely rare with only a single case reported till date. Idiopathic hypoparathyroidism with systemic sclerosis was diagnosed in a 59-year-old gentleman who had presented with recurrent seizures, instability of gait, skin thickening and tightening over both legs and forearms, and arthritis. Examination was significant for positive Trousseau sign and cerebellar ataxia. Evaluation revealed bilateral symmetrical cerebellar and basal ganglia calcification, sensorineural deafness, low serum calcium, elevated serum phosphorus, normal magnesium, normal vitamin D, low plasma parathyroid hormone, high titer of thyroid peroxidase antibody, positive centromere pattern antinuclear antibody, strongly positive anti-topoisomerase-1 (Scl-70) antibody, nonvisualization of parathyroids on neck ultrasonography and skin biopsy suggestive of hyperkeratosis, increased collagen in dermis, and perivascular lymphomononuclear cell infiltration compatible with scleroderma. Last evaluated 10 months after the diagnosis, his ataxia had improved, he remained seizure-free, Trousseau sign was negative, and he had low-normal calcium calcium with calcium carbonate and calcitriol supplementation and switch from phenytoin to valproate. Further studies are warranted to study the use of serum calcium as a screening test for hypoparathyroidism in patients with systemic sclerosis.