早田 桂, 小松 玲奈, 関野 和, 辰本 幸子, 依光 正枝, 舛本 明生, 石田 理, 野間 純, 吉田 信隆

Kei HAYATA, Reina KOMATSU, Madoka SEKINO, Yukiko TATSUMOTO, Masae YORIMITSU, Akio MASUMOTO, Makoto ISHIDA, Jun NOMA, Nobutaka YOSHIDA

広島市立広島市民病院産科婦人科

Department of Obstetrics and Gynecology, Hiroshima City Hospital

キーワード : prenatal ultrasonography, skeletal dysplasia, hypophosphatasia, prenatal 3D-CT, hypochondrogenesis

骨系統疾患は100種類以上存在するが，個々の疾患頻度は低く診断に苦慮することが多い．中には予後不良な疾患も含まれ，正確な出生前診断を要する．今回，骨系統疾患を同時期に2例経験したので報告する．症例1は24歳．妊娠29週に大腿骨短縮を指摘され紹介．四肢全て短縮のため全肢節短縮型骨系統疾患と診断．胎児頭蓋内構造は明瞭に描出され，超音波プローブで胎児の頭蓋を圧迫すると骨変形を認め，hypophosphatasia（低フォスファターゼ症）を疑った．3D-CTでは頭蓋骨や椎体，両手足指の描出は骨化不良のため困難であった．出生児は生後20分後に死亡し，臍帯血ALP 5IU/Lであった．症例2は31歳．妊娠20週に大腿骨短縮を指摘され紹介．四肢全て短縮のため全肢節短縮型骨系統疾患と診断．大腿骨の短縮と骨幹端の末広がり，胸郭低形成より予後不良な四肢短縮症を疑い，正確な出生前診断には至らずも，同意のもと中期中絶を行った．後日死産児の全身Ｘ線写真よりhypochondrogenesis（軟骨低発生症）と診断した．2症例とも一般的に生命予後不良な四肢短縮症である．超音波補助診断として，近年3D-CTの有用性が報告され，胎児超音波によりスクリーニングを行い，3D-CTで確定診断を行う方法が適切との見方もある．3D-CTでは長管骨の計測に加え，細かい形態の変化や骨化の程度といった超音波では描出し難い所見を得ることが可能とされるからである．大腿骨短縮を認めた場合は四肢全ての計測を行い，胸郭低形成の有無を確認し，重症度の鑑別診断が重要である．

Skeletal dysplasia is a rare disease and has numerous classifications, so accurate prenatal diagnosis is difficult. Hypophosphatasia and hypochondrogenesis, in particular, have a poor prognosis. Therefore, assessment of the prognosis is the key to successful management. We report two cases of hypophosphatasia and hypochondrogenesis detected by ultrasonography. Case 1: A 24-year-old primigravida was referred to our hospital at 29 weeks due to shortening of the fetal femur. Ultrasonography demonstrated shortening of all long bones. The skull yielded easily to pressure with the probe. The skull, vertebral bodies, and bilateral hands and feet were not detected by 3D-CT. Based on these findings, hypophosphatasia was strongly suspected. The female baby weighed 2436 g and was delivered with an Apgar score of 1(1’)/1(5’). She died 20 minutes after delivery due to respiratory failure. Her phosphatase value was 5 IU/L. Case 2: A 31-year-old multigravida was referred to our hospital at 20 weeks due to shortening of the fetal femur. Ultrasonography demonstrated shortening of all long bones. The femur looked like metaphyseal splaying. The skull did not yield easily to pressure with the probe. The thorax was very small. Based on these findings, lethal osteochondrodysplasia was strongly suspected. The patient had an abortion. Accurate assessment of the prognosis is the key to successful management. Therefore, it may be clinically significant to measure all bones and examine them carefully using 3D-CT.