New Onset Guttate Psoriasis Following Pandemic H1N1 Influenza Vaccination.

Since the introduction of H1N1 influenza vaccine in the wake of the 2009 H1N1 pandemic, many serious and non-serious vaccine-related adverse events have been reported. The vaccination could induce pain, erythema, tenderness, and induration on injected areas. These symptoms usually disappear in a few days after the vaccination. In this case, we observed a 26-year-old woman with multiple erythematous scaly macules scattered on the extremities and trunk. She was injected with an inactivated split-virus influenza A/H1N1 vaccine without adjuvant (Greenflu-S®, Green Corp.) on her left deltoid area 10 days earlier. The first lesion appeared on the injection site three days after the vaccination, and the following lesions spread to the trunk and extremities after a few days. Histopathological examinations showed neutrophilic collections within the parakeratotic cornified layer, moderate acanthosis, diminished granular layer, elongation and edema of the dermal papillae, and dilated capillaries. The lesions were successfully treated with topical steroids and ultraviolet B phototherapy within three weeks, and there was no relapse for the following fourteen months. We assumed that pandemic vaccination was an important trigger for the onset of guttate psoriasis in this case.