An unusual case of neonatal seizures as manifestation of asymptomatic maternal hypoparathyroidism

Abstract

Neonatal hypoparathyroidism is one of the rare causes of hypocalcaemia. Several cases of neonatal hypoparathyroidism secondary to maternal hyperparathyroidism have been reported. In this case report, we have a term neonate with normal birth history who presented with late onset hypocalcemic seizures. After excluding polyendocrinopathies and related syndromes, hypocalcaemia seizures were secondary to maternal asymptomatic hypoparathyroidism. Since this is one variety of unusual case of maternal and fetal hypoparathyroidism, further testing was mandatory to confirm familial origin. This focuses on the need for every clinician to test maternal metabolic status in case of neonatal manifestations.

Background

Neonatal seizures have diverse aetiology and hypocalcaemia is one of the treatable metabolic causes.¹ Neonatal hypocalcaemia may be early or late onset, transient or permanent and primary or secondary. Hypoparathyroidism is one of the rare causes of late onset neonatal hypocalcaemia. Hypoparathyroidism can be isolated or can occur as a part of maternal factors, polyendocrinopathy, autoimmune disorders or dysmorphic syndromes like CATCH 22, DiGeorge, velocardiofacial defect.^{2 3}

Case presentation

A 28-day-old male full-term neonate, born to non-diabetic mother with uneventful birth history, on breast feeds presented with complaints of multiple episodes of seizures since day 4 of life. No history of maternal illness or drug intake during pregnancy. No history of polyendocrinopathies or calcium disorders in the family. On examination, baby was alert and active. Vitals were stable. No dysmorphic features. Anthropometric data at 50th centile. Systemic examination was normal.

Investigations

Results of investigations revealed normal blood parameters and sepsis screening were negative. Serum calcium level was low (6.5 mg/dL), serum phosphorus was high (7.5 mg/dL), serum magnesium was low (1.9 mg/dL) and alkaline phosphatase (680IU/L). Despite magnesium correction, calcium levels were still low. Vitamin D3 was normal (30 ng/mL) and parathyroid hormone was low (1.0 pg/mL). ECG revealed prolonged QT interval.

Neurosonogram was normal. X-ray chest and echocardiogram was done to rule out DiGeorge syndrome and it was normal. Ultrasonogram (USG) abdomen showed no evidence of nephrocalcinosis and renal anomalies. CSF analysis was normal. Inborn error of metabolism screening (arterial blood gas (ABG), lactate and ammonia) was normal. Audiology evaluation was within normal limits. Assessment of maternal calcium, phosphorus and PTH levels was suggestive of asymptomatic hypoparathyroidism.

Hence, a diagnosis of congenital primary hypoparathyroidism was made.

Treatment

Seizures got controlled with intravenous calcium and magnesium and oral Vitamin D3 as per standard protocol. Baby was discharged with oral calcium, magnesium, Vitamin D3 and regular follow-up. Due to financial problems, PTH supplementation could not be done. Mother was given calcium and Vitamin D3 supplements as well.

Outcome and follow-up

At 1-month follow-up, baby is seizure free with normal serum calcium level.

Discussion

In this case, after interpreting serum PTH levels with calcium levels, a diagnosis of primary hypoparathyroidism was made. DiGeorge syndrome was unlikely. Most of the cases of neonatal hypoparathyroidism is secondary to maternal hyperparathyroidism as it suppresses the fetal PTH activity.¹ In this case, both maternal and fetal hypoparathyroidism could be familial disorder with inheritance by autosomal dominant, recessive or X-linked modes of transmission that requires further genetic testing.

Learning points.

• Unusual causes of common presentations should always be considered.

• Evaluation of the mother is mandatory in case of serious neonatal symptoms.

• Genetic testing is contributory in diagnosis of cases with familial inheritance.