PReS-FINAL-2251: Influenza myositis outbreaks: clinical and laboratory findings

Results Overall 42 subjects were identified from 2000-2009, during peak flu-season and 35 (27 boys) were included. Median onset age was 7 years. Target diagnosis was reported in 89%, during first emergency visit. Observed acute respiratory symptoms, cough (31%) and coriza (23%), with fever (63%) had mean duration of 4.3 days. Muscle-skeletal symptoms were calf-pain (80%), limited walking (57%), abnormal gait (40%), muscle weakness on lower limbs (71%), all with mean duration of 3.6 days. There was a remarkable peak of muscle enzymes, CK (5,507 ± 9,180) U/l, LDH (827 ± 598) U/l and AST (199 ± 245) U/l, and also trends to leukopenia (4,59 × 10 ± 1,42 × 10) n/mm3. Full recovery with laboratory parameters back to normal occurred within 30 days (median). One relapse was identified with 10 months interval. Virus identification was not obtained.