Pseudohypoparathyroidism (PHP) is a rare group of genetic disorders characterised by end-organ resistance to parathyroid hormone (PTH). We describe the case of a 34-year-old Caucasian female with severe hypocalcaemia presenting with a first generalised seizure. Her medical history was significant for bilateral cataract. She had three healthy children, and no family history of note. On examination, she had positive Chvosteks sign. Biochemical analysis showed serum calcium 4.5 mg/dl (n.r. 8.410.2 mg/dl), phosphorus 5.8 mg/dl (n.r. 2.34.7;mg/dl), PTH 94.7 pg/ml (n.r. 14.7673.1 pg/ml) and vitamin D 19.6 ng/ml (n.r. 30100 ng/ml), with normal serum albumin and normal alkaline phosphatase. Electrocardiogram demonstrated prolonged corrected QT interval. Brain imaging revealed basal ganglia and cerebellar calcifications, and electroencephalography did not show paroxysmal activity. We excluded a number of causes of secondary hyperparathyroidism based on her medical history and investigations, and concluded that PTH resistance would be the most likely diagnosis. Since she lacked the typical clinical features of Albright hereditary osteodystrophy and did not present with other hormones resistance, a genetic test was requested and identified abnormal methylation of the 20q13.32 region, confirming the diagnosis of PHP type Ib. The patient is currently medicated with calcium carbonate and calcitriol, maintaining a satisfactory calcium-phosphate homeostasis. This case highlights the importance of PHP as a rare but significant cause of severe hypocalcaemia. The delayed diagnosis, as seen in this case, may result in serious consequences.
20 - 23 May 2017
European Society of Endocrinology