IDIOPATHIC THROMBOCYTOPENIC PURPURA
Idiopathic thrombocytopenic purpura (ITP)4 is an autoimmune condition resulting in increased platelet destruction secondary to antiplatelet antibodies. It is the most common cause of isolated thrombocytopenia in otherwise well children. It can manifest as sudden onset bruising, petechiae, or mucosal hemorrhage, usually after a viral upper respiratory infection and rarely after live vaccinations. On physical exam, lymphadenopathy might be present secondary to the viral infection, but other systemic signs are absent. Isolated low platelet count below 50 X 103/μL with an elevated mean platelet volume and a normal hemoglobin and total white cell count is the only significant laboratory finding. Most cases are self-limiting within 1 to 4 weeks and treatment with oral steroids, intravenous immunoglobulin (IVIG), or anti-D IG is reserved for children with severe hemorrhage or platelet count less than 20 X 103/μL.
Normal platelet count ruled out ITP in this patient.
Henoch-Schonlein purpura (HSP) is an immune-mediated, small-cell vasculitis and can mimic different conditions depending on the system involved: Abdominal pain secondary to gastrointestinal (GI) involvement can present as acute abdomen; joint involvement may mimic juvenile idiopathic arthritis (JIA), rheumatic arthritis, or gonococcal arthritis; and the rash can look similar to ITP, rickettsial diseases, sepsis, or disseminated intravascular coagulation. Laboratory tests are nonspecific for HSP, and more useful is ruling out other potential causes of the presenting symptoms.
Given the characteristic purpuric rash in this otherwise well-appearing patient, along with laboratory findings ruling out the other potential causes, a diagnosis of HSP was made.
Henoch-Schonlein purpura is the most common systemic small-vessel vasculitis in children.5 The mean age of presentation is 6 to 10 years, and the incidence is known to be equal in boys and girls. The disease is more common in autumn and spring.
ETIOLOGY AND PATHOGENESIS
The classical pathogenic feature of HSP is deposition of IgA immune complexes in the vessel walls of the kidney and other affected organs. These in turn activate the complement pathway that triggers the inflammatory cascade leading to the clinical picture discussed. The most common trigger for HSP is known to be upper respiratory infection.5 Several other viruses and bacteria including but not limited to influenza, parainfluenza, Epstein-Barr virus (EBV) and Streptococcus have been associated with HSP.
There have been associations of certain vaccinations such as influenza, meningococcal, measles/mumps/rubella (MMR), and pneumococcal as well as certain drugs with the onset of HSP. However, these associations have not been proven to be linked to causality, and in most cases such associations have been presumed coincidental.
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