Post Streptococcal Myalgia or Protracted Febrile Myalgia - Can we Differentiate them at Presentation?

Myalgia is a common complaint in the pediatric population and can be caused by multiple conditions. Post streptococcal myalgia is an underrecognized entity. Although it was first reported in 1986 by Harats et al (1); less than 10 cases are described in the literature (2). In most of the cases there are fever and high inflammatory marker (2). A similar presentation can be seen in protracted febrile myalgia syndrome (3). we will describe 2 patients who we diagnosed with post streptococcal myalgia and will compare their presentation to our FMF patients who had protracted febrile myalgia syndrome.

Case 1: A 5-year-old girl with 10-days history of muscle pain and inability to ambulate. The symptoms appeared few days following a culture-proven GAS pharyngitis. She was febrile with elevated CRP of 160 mg/dl and ESR of 150 mm/hour. During her hospitalization intensive work-up was done with negative results. The patient`s clinical status improved dramatically with steroids treatment.

Case 2: An 18-year-old female presented with 1-day history of worsening leg pain. Ten days prior to her presentation she was diagnosed with acute pharyngitis and peri-tonsillar abscess. The intensity of the pain prevented her to ambulate. ESR and CRP were elevated at 150 mm/h and 120 mg/L, respectively. ASLO was high at 800 units/mL (later increased to 1269 units/mL). Further laboratory tests were unremarkable. MRI of the lower extremities demonstrated a mild diffuse and symmetric inflammatory response. Naproxen was started with good clinical response. For both patients Genetic testing to FMF was negative.