SAT-742 Pseudohypoparathyroidism Presenting With Extensive Intracranial And Subcutaneous Calcifications: A Case Report

Abstract Disclosure: A. Shahatit: None. A. Banka: None. L. De Mattei: None. B. Celik: None. J. Meireles: None. U. Bin Hameed: None. Introduction: Pseudohypoparathyroidism (PHP) is a rare disorder marked by end-organ resistance to parathyroid hormone (PTH), leading to hypocalcemia and hyperphosphatemia despite elevated PTH. Chronic PHP may result in basal ganglia calcifications (BGC), contributing to neurological complications. Case Presentation: A 44-year-old man with hypertension, hypothyroidism, and prior strokes with residual aphasia and right-sided weakness was referred for severe hypocalcemia. On exam, he had short stature. Labs showed: calcium 4.8 mg/dL (normal: 8.5-10.5), ionized calcium 2.53 mg/dL (4.6-5.3), phosphorus 6.7 mg/dL (2.5-4.5), PTH 218 pg/mL (10-65), vitamin D 66.2 ng/mL (30-100), creatinine 0.87 mg/dL (0.6-1.2), and TSH 9.98 µIU/mL (0.4-4.0). Head CT revealed extensive calcifications in the posterior fossa, deep gray nuclei, subcortical frontal and temporal lobes, and subcutaneous scalp tissues. The patient reported lifelong hypocalcemia and prior imaging showing brain calcifications. He was non-adherent to levothyroxine.He was treated with IV calcium gluconate followed by oral calcium citrate, calcitriol, and levothyroxine. Calcium normalized (to 8.0 mg/dL), and he was discharged on calcium carbonate, calcitriol, and levothyroxine with endocrinology and neurology follow-up. Discussion: This case highlights classic PHP features: hypocalcemia, hyperphosphatemia, elevated PTH, and extensive tissue calcifications. BGC in PHP is linked to seizures, movement disorders, and cognitive deficits. Coexisting hypothyroidism may reflect TSH resistance, often seen in PHP Type 1a due to GNAS mutations, which impair Gs alpha protein signaling in multiple hormone pathways. Learning Points:Suspect PHP with hypocalcemia, hyperphosphatemia, and high PTH in the setting of normal renal function.Intracranial and subcutaneous calcifications may signal long-standing disease.PHP Type 1a may include TSH resistance and other hormone resistance syndromes.Lifelong calcium and active vitamin D therapy is essential. Conclusion: This case emphasizes the importance of recognizing PHP early to prevent irreversible neurologic complications and highlights diagnostic clues from labs and imaging. Presentation: Saturday, July 12, 2025