Review Question - QID 108620

This patient is presenting with signs and symptoms of Henoch-Schonlein purpura (HSP), a small vessel vasculitis that classically occurs in children one week after a viral respiratory illness. HSP is caused by the deposition of circulating IgA immune complexes in small vessels.

In this vignette, the patient's history of a recent upper respiratory illness and her presenting symptoms are important clues to identify HSP. Purpura are purple-colored spots on the skin that are caused by microvascular bleeding. They can be caused by a wide range of illnesses including immune thrombocytopenic purpura, bacterial illnesses such as Neisseria meningitidis, vessel fragility in the elderly, or venous stasis. The features of this patient's presentation that are critical to the diagnosis include her abdominal pain, arthralgia, and hematuria. In HSP, circulating IgA immune complexes secondary to resolving respiratory infection deposit in small vessels of the skin, GI tract, kidney, joints, and sometimes lungs. Therefore, patients may present with multiple complaints across these organ systems.

Figure A shows the classic appearance of purpura in HSP. They may appear anywhere on the body, but are most commonly found on the lower extremities and buttocks.

Incorrect Answers:
Answer 1: Thrombocytopenia can be be a cause of purpura. Platelets are important in the clotting process so deficiency of platelets can lead to bleeding of small vessels, resulting in purpura. The normal complete blood count in the patient rules out this option.

Answer 2: Urticaria (hives), are caused by mast cell degranulation. Unlike the rash described in this patient, hives are red, raised, and blanch with palpation.

Answer 3: Blue or black purpura can be observed in N. meningitidis and Streptococcus pneumoniae. These patients typically are toxic appearing, with high fevers, hypotension, and may progress to disseminated intravascular coagulation.

Answer 5: Venous stasis can result in purpura. This is typically observed in elderly patients, and is associated with obesity and a sedentary lifestyle.

Bullet Summary: Henoch-Schonlein purpura occurs in children approximately one week after a viral respiratory illness. It presents with purpuric rash of the lower extremities and buttocks, abdominal pain, arthralgia, and hematuria.