Neonatal seizures due to maternal primary hyperparathyroidism.

Abstract

We would like to report a rare case of asymptomatic maternal hyperparathyroidism due to a parathyroid adenoma presenting with recurrent neonatal hypocalcaemic seizures in her offspring. Following an uneventful pregnancy, a 36-year-old gravida 3 para 2 Chinese shop assistant delivered a 3000-g male infant at term gestation via elective lower segment Caesarian section. He was discharged on the fourth day of life and remained well until the tenth day of life when he developed multiple brief episodes of jerky movements of his right upper and lower limbs, and twitching of his eyelids. In between these episodes he was well. On the fifteenth day of life, his mother brought him to the hospital as the episodic seizures were becoming more frequent at about 20 times a day. There was no associated fever, diarrhoea or vomiting. He was the third child from a non-consanguineous marriage. There was no family history of seizures. Physical examination revealed a well infant weighing 3880 g, and no abnormalities were detected. His vital signs were normal. There was no dysmorphic features or neurocutaneous stigma. Culture of his blood, urine and cerebrospinal fluid specimens were negative. His serum electrolytes and random blood sugar were all within normal limits. His corrected serum total and ionized calcium levels were 1.12 and 0.4 mmol/L, respectively. His serum magnesium level was 0.56 mmol/L, and serum parathyroid hormone level was 0.916 pmol/L (reference range: 1.3−7.6). He was commenced on intravenous and later oral calcium supplement therapy. His seizures ceased when his serum calcium level rose above 1.4 mmol/L. His serum calcium level became normal when he was treated with alpha-calcidol at 0.3 mg per day and calcium lactate at 300 mg four times a day. Supplemental therapy with calcium and vitamin D was reduced from the age of 2 months and stopped altogether when he was 3 months old. His serum calcium level remained normal subsequently. Laboratory investigation revealed that his mother had high serum calcium (3.11 mmol/L), low serum phosphate (0.59 mmol/L) and high serum parathyroid hormone (239.5 pmol/L). Ultrasonography showed an enlarged parathyroid gland behind the middle and lower pole of the right lobe of her thyroid gland. Her abdominal ultrasonogram revealed the presence of gallbladder calculi and bilateral medullary nephrocalcinosis. At surgery, she was found to have an enlarged right inferior parathyroid gland measuring 25 × 12 mm and weighing 1.5 g, which was excised. Histopathological examination of this specimen confirmed the presence of a parathyroid adenoma. Post-operatively she developed symptomatic hypocalcaemia for which she was treated with oral calcium supplement. Review of medical literature showed that maternal primary hyperparathyroidism during pregnancy is rare with an estimated incidence of eight per 100 000 population per year1−6. A majority of these women are asymptomatic or have subtle symptoms due to physiological changes of calcium metabolism during pregnancy. Morbidity in both mother and her infant, as shown in our patients, was high. In mothers who were not treated, the incidence of foetal complications was reported to be as high as 80%; these included intrauterine growth restriction, low birthweight, preterm delivery, intrauterine death and neonatal hypocalcaemic tetany and seizures2. The neonatal hypocalcaemia results from intrauterine suppression of foetal parathyroid function by the maternal hypercalcaemia, sudden deprivation of a rich source of calcium from its mother after birth, and the neonate's incapability to mobilize calcium from its bones due to its low serum level of parathyroid hormone and high serum level of calcitonin. Most infants became symptomatic at the end of first week of life with seizure, as was found in our patient3,4, requiring short-term calcium supplemental therapy of 3 to 5 month duration until the hypoparathyroidism resolves. Our case illustrates that when newborns present with hypocalcaemic seizures towards the end of the first week of life or later, appropriate investigations should be carried out to exclude maternal hyperparathyroidism.