児の低Ca 血症を契機に，副甲状腺機能異常と診断した母児例を経験した。日齢5 の正期産の女児は，黄疸治療 目的の入院中に，低Ca 血症，高P 血症を認めた。intact-PTH は低下しており，副甲状腺機能低下症と診断した。 母に自覚症状はなかったが，血液検査を行ったところ，高Ca 血症，低P 血症，intact-PTH の異常高値を認め，副 甲状腺機能亢進症が判明した。さらに，母児ともにビタミンD 欠乏症が明らかで，生後早期の低Ca 血症の進行に 関与したと考えられた。
新生児の低Ca 血症は，児の基礎疾患の評価とともに，母体要因の検索を行う必要がある。
We report a case of a 5-day-old, full-term female infant who presented with asymptomatic hypocalcemia. The infant underwent phototherapy for neonatal jaundice under the supervision of a pediatrician, and hypocalcemia was incidentally detected. Additional laboratory tests indicated hypoparathyroidism and vitamin D deficiency. Subsequently, asymptomatic maternal hyperparathyroidism and vitamin D deficiency were also detected. The infant was asymptomatic with no pertinent past medical or family history. Maternal hyperparathyroidism and vitamin D deficiency resulted in neonatal hypoparathyroidism and vitamin D deficiency. In particular, vitamin D deficiency in the setting of hypoparathyroidism caused rapid progression of neonatal hypocalcemia.
Neonatal hypoparathyroidism can be attributed to maternal parathyroid disorder. If neonatal parathyroid dysfunction or disorders of calcium metabolism are confirmed, evaluations of maternal factors are warranted. Even if the mother is asymptomatic, unrecognized maternal disease could be incidentally detected. In addition, the coexistence of vitamin D deficiency and hypoparathyroidism could exacerbate neonatal hypocalcemia.
