環状13番染色体症候群症例の側頭骨病理所見

Temporal Bone Pathology in a Case of Ring Chromosome 13

　はじめに

　環状13番染色体症候群（以下，13リング症候群）は13番染色体が環状構造をとる染色体異常症であり，Niebuhr^1）はその臨床徴候より13q-症候群の1型として分類している。臨床所見としては，重度の精神発達遅滞，中枢神経の異常，心・腎の奇形，小頭症，鎖肛，生殖器異常，翼状頸などの外表奇形が指摘されており，耳科学的所見として，耳介奇形，低在耳介を認めることがあると報告されている^2〜5）。

　しかしその側頭骨病理所見については，われわれの検索したところでは報告されていない。今回われわれは13リング症候群の側頭骨病理を観察する機会を得たので報告する。

Ring 13 syndrome, a congenital abnormality as-sociated with a ring chromosome 13, is character-ized by severe mental retardation, visceral anom-alies, and external deformities. We report the path-ologic features in the temporal bone from a 7-month -old patient with ring 13 syndrome.

On the left side, the cochlea was short and the cochlear axis was hypoplastic in the inner ear. The utricular macula was collapsed, and the vestibular nerve fibers were decreased in number. The ampul-lae of the anterior and lateral semicircular canals were hypoplastic. The facial nerve had an abnormal course in the middle ear.

On the right side, the vestibule exhibited deform-ities in the membranous labyrinth and there were residual cartilages in the inner ear. The non-ampul-lar end of the lateral osseous semicircular canal was hypoplastic. The facial nerve had an abnormal course and nerve fibers were reduced, while the stapes was hypoplastic.

The temporal bone pathology in our case of ring 13 syndrome was characterized not only by ectoder-mal anomalies in the inner ear, but also mesodermal anomalies, such as an abnormal course of the facial nerve.