This is a literature case, initially received from other health professional on 26-Nov-2018, concerning a 19-year-old, male patient. The patient's historical condition included severe seasonal allergies. On an unspecified date (ten days prior to the onset of symptoms), the patient was administered influenza vaccine (route of administration: subdermal, dose, anatomical location, batch number, manufacturer, trade name and expiry date: not reported). On the same day, the patient was administered an additional dose of INN flu vaccine seasonal, intramuscularly. Two days after vaccination, the patient developed dry cough, rhinorrhea, malaise and diffuse myalgia. The patient had three episodes of vomiting for the last two days accompanied by headache, malaise and weakness, before he went to an emergency on an unspecified date (reported as February). The purpuric rash on the extremities was noted which was not associated with pain, burning sensation or pruritus. During the initial physical examination, the patient was well appearing, afebrile, and with normal vital signs. There was no oropharyngeal erythema, oral lesions or lymphadenopathy. The patient developed a palpable non-blanching purpuric rash on the calves, knees and elbows but most prominently on the ankles. The rest of the physical examination was unremarkable. The patient had leukocytosis (11,500 WBC/uL) with 80 percent neutrophils and normal platelet counts (232,000 platelets/uL). Urinalysis, creatinine and liver function tests were within normal limits and C reactive protein was 7.4 mg/dL. A respiratory viral panel, human immunodeficiency virus enzyme-linked immune sorbent assay (HIV ELISA), rapid plasma reagin (RPR), hepatitis B surface antigen (HBsAg) and hepatitis C virus (HCV) antibodies were negative. Both chest X-ray and cerebrospinal fluid (CSF) analyses showed no abnormalities. C3 and C4 levels were decreased but the rest of the rheumatologic panel [anti-double stranded DNA (anti-dsDNA), Anti-Ro, Anti-La, Anti-SM, Anti-RMP and antineutrophil cytoplasmic antibodies) were negative. After 72 hours in hospital, the patient developed abdominal pain, bloody diarrhoea and left scrotal pain. Patient's testicular ultrasound showed mild varicocele and an abdominal computerised tomography (CT) scan showed thickening of the ascending colon walls. The patient was diagnosed with IgA vasculitis or Henoch-Schonlein Purpura (HSP). The patient received symptomatic pain management, along with one dose of intravenous methylprednisolone, followed by three additional doses of oral prednisone when the gastrointestinal bleeding resolved. The patient was discharged once the oral corticosteroid regimen was completed, as there was no recurrence of the gastrointestinal bleeding. The rest of the symptoms resolved within two weeks after hospital admission. At six months follow up, the patient did not have any recurrence and never developed kidney dysfunction. The outcome of the event was recovered. The reporter assessed this case as serious due to hospitalization. The reporter concluded that the large antigenic trigger due to the unusual dose might have contributed to the development of the disease (related).