七條 光市, 森 一博, 小野 朱美, 渡邊 浩良

Koichi SHICHIJO, Kazuhiro MORI, Akemi ONO, Hiroyoshi WATANABE

徳島県立中央病院小児科

Department of Pediatrics, Tokushima Prefectural Central Hospital

キーワード : nodular lymphangitis, linear erythema, ultrasonography, cutaneous nocardiosis, pediatric

症例は3歳男児．左膝に擦過傷を負った1週間後に，発熱と歩行困難を主訴に当院を受診した．来院時の身体所見で左膝創部から左鼠径部にかけて，左大腿部の線状発赤を認めた．超音波検査では，線状発赤に一致したリンパ管の拡張，数珠状リンパ節腫脹，周囲脂肪組織の輝度上昇を認めた．左鼠径部リンパ節は腫大し，輪郭やや不整で，血流信号の明らかな増加は認めず，膿瘍形成も認めなかった．血液検査は，WBC 13,000/μL，CRP 3.7 mg/dLであった．セファゾリン120 mg/kg/日の静脈内投与を開始したが，反応は不良であった．外傷の病歴と特徴的な超音波所見から皮膚ノカルジア症を疑い，入院3日目に抗生剤をスルファメトキサゾール・トリメトプリム（ST合剤）0.1 g/kg/日の内服へ変更した．以後は症状が改善傾向となり，入院5日目に退院した．退院翌日に，前医で提出された左膝創部の排膿培養にてNocardia brasiliensis検出の報告があった．ST合剤の感受性は良好であった．以後症状の再燃を認めず，退院4週間後にST合剤内服を終了した．皮膚ノカルジア症の報告は少ないが，本症が十分認識されていない可能性がある．身体診察が困難な乳幼児において，外傷を契機とした皮膚軟部組織感染症を疑う場合には超音波検査を行い，同部位にリンパ管拡張および数珠状リンパ節腫脹を認めた場合は皮膚ノカルジア症を考慮する必要がある．

A 3-year-old boy was referred to our hospital with the complaint of fever, redness on the left thigh, and difficulty walking. History-taking revealed that he had injured his left knee 1 week prior to presentation. On presentation, clinical examination revealed linear erythema on the left thigh. Ultrasonography revealed lymphatic dilation in the same area, beaded enlarged lymph nodes, and increased echogenicity of the surrounding adipose tissue. A left inguinal lymph node was also enlarged, with slightly irregular margins. Blood flow to the lymph node was not obviously increased, in the absence of an abscess. Blood tests showed a white blood cell count of 13,000/μL and a C-reactive protein level of 3.7 mg/dL. Intravenous cefazolin 120 mg/kg/day was initiated, but the response was poor. Because cutaneous nocardiosis was suspected based on the clinical findings, the antibiotic was switched to oral trimethoprim-sulfamethoxazole (TMP-SMX) on day 3 of hospitalization. The patient was discharged on the 5th day of hospitalization with improved clinical and hematological findings. Subsequently, culture of the fluid previously drained from the knee was positive for Nocardia brasiliensis sensitive to TMP-SMX. There was no relapse during follow-up and TMP-SMX was discontinued after 4 weeks. Cutaneous nocardiosis is rare but possibly underdiagnosed. Ultrasonography is a useful noninvasive method of diagnosis in children, who are difficult to examine physically. Ultrasonography should be performed if soft tissue infection is suspected following trauma. Cutaneous nocardiosis should be considered in cases of lymphangitis with beaded enlarged lymph nodes on ultrasonography.