Dementia secondary to hypoparathyroidism with the focus on Fahr syndrome

Background: Hypoparathyroidism is a rare endocrine disorder characterised by low, undetectable, or inappropriately normal parathyroid hormone (PTH) secretion, resulting in chronic hypocalcaemia and hyperphosphataemia. While neuromuscular and psychiatric manifestations are well documented, they remain uncommon, and their relationship to cognitive impairment remains under-recognised. Chronic hypocalcaemia may lead to intracranial calcium and phosphate deposition, resulting in Fahr syndrome, a recognised but underappreciated cause of secondary cognitive impairment. There is very limited data concerning the prevalence of neuropsychiatric manifestations of hypoparathyroidism in South Africa.Case: This report describes a 78-year-old woman with primary hypoparathyroidism who presented with cognitive decline, hallucinations, and behavioural changes. Her computerised tomography scan (CT scan) demonstrated bilateral basal ganglia and cerebellar calcification, suggestive of Fahr syndrome. Her CT scan did not show changes in keeping with Alzheimer’s disease or vascular dementia. Despite calcium optimisation, her cognitive impairment persisted.Discussion: Cognitive impairment in hypoparathyroidism is likely multifactorial and although recognised may be challenging to diagnose. Chronic hypocalcaemia disrupts neuronal excitability, affects neurotransmitter release, and alters parathyroid hormone receptor signalling and cerebral blood flow, leading to cognitive deficits. Prolonged disease duration may result in irreversible calcification-related changes. These changes contribute to deficits in attention and executive functioning.Conclusion: Cognitive impairment is an important and under-recognised complication of chronic hypoparathyroidism. Our case highlights that deficits may persist despite biochemical correction, particularly in the presence of intracranial calcification. Incorporating routine cognitive screening into long-term care may support earlier detection and allow for a tailored management plan for affected patients with the aim of mitigating long-term neurocognitive sequelae.