POLR3A遺伝子変異を認めたPolⅢ関連白質ジストロフィーの1例

A Case of PolⅢ-related Leukodystrophy with Homozygous Mutation in POLR3A

症例は27歳男性である。学童期から学力不振と運動能力低下が目立つようになり，第二次性徴の発現はなかった。症候性てんかん発症を契機に撮影した頭部MRIで大脳白質髄鞘低形成，脳幹・小脳萎縮，脳梁低形成を認めた。血液検査では低ゴナドトロピン性性腺機能低下症の所見があり，POLR3A遺伝子解析ではc.2350G＞Aホモ接合性変異がありPolⅢ関連白質ジストロフィーと診断した。本疾患は本邦からの報告数が少ないことから，貴重な症例であると考えた。

Abstract

We describe a 27-year-old man with mental retardation, symptomatic epilepsy, myopia, and cerebellar ataxia without spontaneous puberty whose brain magnetic resonance imaging showed hypomyelination. He had child-like facial appearance, with thin facial hair. He had no underarm and pubic hairs, and his penis was small. Laboratory tests showed low levels of luteinizing hormone, follicle-stimulating hormone, and testosterone. Brain MRI showed diffuse hypomyelination, atrophy of the cerebellum and brainstem, and hypoplastic corpus callosum. Ictal N-isopropyl-p-(indone-123)-iodoamphetamine single photon emission computed tomography (¹²³I-IMP SPECT) revealed hypoperfusion of bilateral frontal cingulate and temporal lobe and cerebellar hemispheres. Homozygous missense mutation c.2350G＞A was found in POLR3A and the patient was diagnosed with PolⅢ-related leukodystrophy, which is a rare disease. We describe the present case in light of the characteristics of the past reports in Japan.

(Received April 5, 2016: Accepted June 30, 2016; Published November 1, 2016)