Miositis aguda asociada a infección por virus influenza. Serie de casos en un hospital pediátrico / Acute myositis associated with influenza infection. Case series in a pediatric hospital

La miositis aguda benigna asociada a influenza es una complicación esporádica. En Argentina, en el año 2022, hubo un aumento temprano de la circulación de influenza y del número total de las notificaciones, con la aparición de miositis secundarias. Serie clínica retrospectiva de nueve pacientes pediátricos que consultaron por dolor e impotencia funcional de extremidades inferiores, y enzimas musculares elevadas, en el hospital Pedro de Elizalde de la Ciudad Autónoma de Buenos Aires, entre agosto y octubre del 2022. En todos se detectó infección por virus influenza y se recuperaron sin secuelas. La miositis aguda benigna es una entidad infrecuente en la infancia, cuyo diagnóstico es predominantemente clínico y de recuperación ad integrum. Debe ser sospechada en pacientes con clínica compatible en contexto de alta circulación viral. La vigilancia epidemiológica aporta herramientas para identificar los virus circulantes y sus posibles complicaciones.

Benign acute myositis associated with influenza is a sporadic complication. In Argentina, in 2022, there was an early increase in influenza circulation and the total number of notifications, with the appearance of secondary myositis. Retrospective clinical series of nine pediatric patients who consulted for pain and functional impotence of the lower extremities, and elevated muscle enzymes, at the Pedro de Elizalde hospital in the Autonomous City of Buenos Aires, between August and October 2022. In all of them, infection by influenza virus and recovered without sequelae. Benign acute myositis is a rare entity in childhood, whose diagnosis is predominantly clinical and recovery ad integrum. It should be suspected in patients with compatible symptoms in a context of high viral circulation. Epidemiological surveillance provides tools to identify circulating viruses and their possible complications.

Clinical and laboratory description of a series of cases of acute viral myositis / Descrição clínico-laboratorial de uma série de casos de Miosite Aguda Viral

ABSTRACT OBJECTIVE: Describe the clinical and laboratory profile, follow-up, and outcome of a series of cases of acute viral myositis. METHOD: A retrospective analysis of suspected cases under observation in the emergency department was performed, including outpatient follow-up with the recording of respiratory infection and musculoskeletal symptoms, measurement of muscle enzymes, creatine phosphokinase (CPK), lactate dehydrogenase (LDH), transaminases (AST and ALT), blood count, C-reactive protein, and erythrocyte sedimentation rate in the acute phase and during follow-up until normalization. RESULTS: Between 2000 and 2009, 42 suspected cases were identified and 35 (27 boys) were included. The median age was 7 years and the diagnosis was reported in 89% in the first emergency visit. The observed respiratory symptoms were cough (31%), rhinorrhea (23%), and fever (63%), with a mean duration of 4.3 days. Musculoskeletal symptoms were localized pain in the calves (80%), limited ambulation (57%), gait abnormality (40%), and muscle weakness in the lower limbs (71%), with a mean duration of 3.6 days. There was significant increase in CPK enzymes (5507 ± 9180 U/L), LDH (827 ± 598 U/L), and AST (199 ± 245 U/L), with a tendency to leukopenia (4590 ± 1420) leukocytes/mm3. The complete recovery of laboratory parameters was observed in 30 days (median), and laboratory and clinical recurrence was documented in one case after 10 months. CONCLUSION: Typical symptoms with increased muscle enzymes after diagnosis of influenza and self-limited course of the disease were the clues to the diagnosis. The increase in muscle enzymes indicate transient myotropic activity related to seasonal influenza, which should be considered, regardless of the viral identification, possibly associated with influenza virus or other respiratory viruses.

RESUMO OBJETIVO: Descrever o perfil clínico-laboratorial, o acompanhamento e o desfecho de uma série de casos de miosite aguda viral. MÉTODO: Foi conduzida uma análise retrospectiva de casos suspeitos, em observação em unidade de emergência, e seguimento ambulatorial com o registro de sintomas de infecção respiratória, sintomas músculo-esqueléticos, determinação de enzimas musculares, creatina-fosfoquinase (CPK), desidrogenase lática (DHL), transaminases (AST e ALT), hemograma, proteína C reativa e velocidade de hemossedimentação, na fase aguda e no acompanhamento, até a normalização. RESULTADOS: Entre 2000 e 2009, 42 casos suspeitos foram identificados e 35 (27 meninos) foram incluídos. A mediana de idade foi de sete anos e o diagnóstico relatado em 89%, na primeira visita de emergência. Os sintomas respiratórios observados foram: tosse (31%), coriza (23%) e febre (63%), com duração média de 4,3 dias. Os sintomas músculo-esqueléticos foram: dor localizada nas panturrilhas (80%), deambulação limitada (57%), marcha anormal (40%) e fraqueza muscular nos membros inferiores (71%), com duração média de 3,6 dias. Observou-se elevação importante das enzimas CPK (5.507 ± 9.180) U/l, DHL (827 ± 598) U/l e AST (199 ± 245) U/l e tendência a leucopenia (4.590 ± 1.420) leucócitos/mm3. A recuperação completa dos parâmetros laboratoriais foi observada em 30 dias (mediana) e a recaída clínica e laboratorial em um caso após 10 meses. CONCLUSÃO: Os sintomas típicos com enzimas musculares elevadas após diagnóstico de influenza e o curso autolimitado foram os indícios para o diagnóstico. A elevação de enzimas musculares indica a atividade miotrópica transitória relacionada à influenza sazonal que deve ser considerada, a despeito da identificação viral, possivelmente associada com o vírus influenza ou outros vírus respiratórios.

A Case of Myositis due to Influenza B Virus / 감염과화학요법

Benign acute myositis by influenza virus usually occurs in children during recovery from the respiratory illness. It has been mostly reported in Japan and Europe but there has been no report confirmed by virus isolation in Korea. A 4-year-old boy was admitted to the hospital who presented with influenza-like symptoms, painful calves, and difficulty walking. The patient recovered within 5 days without any serious sequelae. We confirmed influenza B virus by RT-PCR and viral culture from clinical specimen. We report a case with acute myositis due to influenza B infection by clinical and laboratory diagnosis.

A Case of Myositis due to Influenza B Virus / 감염과화학요법

Benign acute myositis by influenza virus usually occurs in children during recovery from the respiratory illness. It has been mostly reported in Japan and Europe but there has been no report confirmed by virus isolation in Korea. A 4-year-old boy was admitted to the hospital who presented with influenza-like symptoms, painful calves, and difficulty walking. The patient recovered within 5 days without any serious sequelae. We confirmed influenza B virus by RT-PCR and viral culture from clinical specimen. We report a case with acute myositis due to influenza B infection by clinical and laboratory diagnosis.