American Board of Internal Medicine (ABIM) Certification Practice Exam

What laboratory finding may be elevated in patients with Henoch-Schönlein Purpura?

1. Serum IgM levels

2. Serum IgG levels

3. Serum IgA levels

4. Serum IgE levels

The correct answer is: Serum IgA levels

In patients with Henoch-Schönlein Purpura (HSP), an elevated level of serum IgA is often observed. HSP is a small-vessel vasculitis characterized by a tetrad of symptoms: palpable purpura, often on the buttocks and legs, arthralgia, abdominal pain, and renal involvement. The condition is associated with increased serum IgA levels, which is a notable finding. The role of IgA in HSP may be linked to the pathophysiological mechanisms underlying the disease, such as immune complex deposition and a subsequent inflammatory response in the small vessels. IgA is a class of immunoglobulin that is prominent in mucosal immunity and elevated levels might suggest an abnormal immune response typical of HSP, particularly following a respiratory infection or gastrointestinal infection, which can trigger the onset of the disorder. The other immunoglobulins, such as IgM, IgG, and IgE, do not show a consistent or notable elevation specific to HSP. IgM is typically involved in the early immune response, while IgG and IgE levels might change in various other conditions but are not specifically linked to HSP. Therefore, the elevation in serum IgA levels is particularly relevant to the diagnosis