Clinical and laboratory description of a series of cases of acute viral myositis

ObjectiveDescribe the clinical and laboratory profile, follow‐up, and outcome of a series of cases of acute viral myositis.MethodA 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.ResultsBetween 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 (5,507 ± 9,180 U/L), LDH (827 ± 598 U/L), and AST (199 ± 245 U/L), with a tendency to leukopenia, (4,590 ± 1,420) 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 ten months.ConclusionTypical 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.

ResumoObjetivoDescrever o perfil clínico‐laboratorial, o acompanhamento e o desfecho de uma série de casos de miosite aguda viral.MétodoFoi 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.ResultadosEntre 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.ConclusãoOs 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.