Myositis of Calf Muscle Associated with Influenza B-Report of 4 Cases

Abstract

From February to June, 1980, four children with bilateral calf muscle pain were found. The muscle pain followed one to 4 days after upper respiratory symptoms and was so marked as to be unable to walk. But it subsided to walk on tiptoe within a few days and they recovered 7 to 10 days later without sequellae. Elevations of GOT, CPK and LDH were demonstrated in the acute phase and returned to the normal ranges within 10 days according to clinical improvement. No myoglobinuria observed. Pair sera revealed significant rises of influenza type B CF titer in two of 4 cases, and a type B influenza virus was isolated from the throat in one case. In the other 2 cases, CF titers of influenza B did not show a significant increase or decrease in their two point sera. But their titers were enough to explain the recent infection of influenza B virus and were compatible to the association of transient calf muscle pain.
The HA antigenicity of the virus derived from our case was moderately (4 to 8 folds) drifted from current vaccine strain B/Kanagawa/3/76 on cross HI. B type influenza virus was not predominantly isolated in that season but association with calf muscle pain were not observed on H₃N₂ or H₁N₁ type A influenza that year.