Diagnostic Importance of Creatine Phosphokinase in Viral Myositis: A Case Report

Viral myositis is a transient inflammatory muscle disorder commonly affecting school-aged children following viral infections, particularly influenza, and is often under diagnosed. It typically presents with acute onset muscle pain, calf tenderness, and difficulty in ambulation, while muscle strength and reflexes remain preserved. We report a case of a 7-year-old male child who developed sudden bilateral leg pain and an antalgic gait following a febrile illness. Clinical examination revealed marked calf tenderness without neurological deficits. Laboratory evaluation demonstrated a markedly elevated serum creatine phosphokinase (CPK) level of 44,045.3 U/L( peak level 46,505.9 U/L on day 3 Table 1) with normal renal function parameters. A diagnosis of acute viral myositis was established, and the child was managed conservatively with adequate hydration and close biochemical monitoring. The patient showed rapid clinical recovery with normalization of gait and a progressive decline in CPK levels. This case underscores the diagnostic value of serum CPK in identifying viral myositis and differentiating it from serious neuromuscular conditions, thereby preventing unnecessary investigations and overtreatment. Early recognition and supportive management ensure excellent outcomes in affected children.