A previously healthy 14-year-old girl presents in mid-winter season a 12-hour history of fever, headache and pruritic exanthema affecting face, trunk and limbs. Vital signs, including blood pressure, were normal. Observation revealed a generalized confluent maculopapular exanthema and angioedema of the face, with no signs of bleeding diathesis. Nonexudative tonsillitis was diagnosed seven days before treated with amoxicillin. A serologically confirmed Epstein-Barr virus (EBV) infection two years before was reported. Allergies or previous urticaria were denied. She was not taking medication, consumed new foods nor new skin-care products. Despite corticoid and antihistamine treatment, the exanthema worsened, affecting palms (Fig. 1) and soles, progressing to purpuric (Fig. 2) with intense pruritus, and the patient was hospitalized. Coagulation and complete blood cell count were normal, without eosinophilia. C-reactive protein, hepatic enzymes and urinalysis were unremarkable. Etiological investigation for virus (CMV, herpesvirus, enterovirus, parvovirus, respiratory viruses), bacteria (Chlamydia pneumoniae, Mycoplasma penumoniae, Borrelia burgdorferi, Coxiella burnetti, Treponema pallidum, Steptococcus pyogenes), blood and stool culture and parasites were negative. There was no EBV reactivation (EA-IgG negative/VCA-IgM negative/VCA-IgG positive/ EBNA-IgG positive). Nasal/throat swab screening by real-time polymerase chain reaction was positive for Influenza B. Autoimmunity screening was negative, as well as specific immunoglobulin E for amoxicillin and ibuprofen, with no recurrence after re-exposure. Fever lasted 24 hours and the rash disappeared in five days.

Figure 1: Macular exanthema 24 hours after the onset of generalized urticaria affecting palms (A) and dorsum (B) of both hands. 

Figure 2: Macular and purpuric exanthema affecting the upper limb (24 hours after the onset of disease). 

Generalized pruritic exanthema as a manifestation of influenza has been rarely reported. Descriptions of rash associated to influenza B infection occur in children, usually nonpruritic maculopapular sparing palms and soles.^1-3

According to the Portuguese Influenza National Surveillance Program, Influenza B was the main subtype circulating in this period (79%).⁴ Influenza B viral shedding is bimodal, exhibiting a second peak 24-to-48 hours after the onset of symptoms, and rapidly declining.⁵ Both arguments favor the association between influenza B and exanthema, although causality cannot be established.