Vaccination details:
(1) The infants were receiving DTP-IPV plus (Hib1 or Hib2) = Diphtheria-pertussis-tetanus-polio plus Haemophilus influenzae b.
(2) Most episodes occurred after the first and/or second vaccination dose. The first dose was usually given at 3 months of age.
(3) The vaccine is given IM in the upper leg if the child is under 2 years of age.
Features of the discolored leg syndrome:
(1) The onset was sudden and within a few hours after vaccination but could be delayed.
(2) The legs showed one or more of the following:
(2a) even or patchy reddish color
(2b) even or patchy bluish color
(2c) even or patchy purplish color
(2d) petechiae
(2e) swelling
(3) The reaction may involve all or part of one or both legs with or without involvement of the pelvis (“trouser” pattern)
(4) Most children had fierce crying. Additonal symptoms included pallor and cyanosis. Fever was variable.
(5) The condition was self-limiting, with changse lasting from a few hours for a discoloration and for up to 54 hours for petechiae.
(6) The reaction does not extend to the injection site.
(7) There were no apparent sequelae following recovery. The parents may become distraught, especially if the reaction is severe.
Differential diagnosis:
(1) extensive local reaction (which would involve the injection site)
(2) cellulitis
(3) concurrent infection
