A 20-year-old man is brought to the emergency department because of abdominal pain and vomiting. He has had mid-abdominal pain and dark stools for the last two days and his appetite has decreased. Over the last week, he has been 'feeling down' and has noticed a rash over both thighs. He denies any fever, chills, back pain, or diarrhea.
He suffered from mild intermittent asthma as a child but otherwise has an unremarkable past medical history. He does not smoke or consume alcohol. He denies any illicit drug use except for smoking marijuana several times in the past. He went camping in Vermont three weeks ago and travelled to Eastern Europe six months ago. While in Eastern Europe he had several bouts of diarrhea. He is sexually active with his girlfriend and uses condoms regularly.
His temperature is 36.7 C (98 F), blood pressure is 122/76 mmHg, and pulse is 98/min. On physical examination, no murmurs are heard. His abdomen is mildly tender without rebound. Stool for occult blood is positive. There are crops of purple non-blanching lesions affecting both thighs. Neurologic examination is unremarkable.
Laboratory results are as follows:

Which of the following is most likely to establish this patient's diagnosis?

Question

A 20-year-old man is brought to the emergency department because of abdominal pain and vomiting.  He has had mid-abdominal pain and dark stools for the last two days and his appetite has decreased.  Over the last week, he has been 'feeling down' and has noticed a rash over both thighs.  He denies any fever, chills, back pain, or diarrhea.
He suffered from mild intermittent asthma as a child but otherwise has an unremarkable past medical history.  He does not smoke or consume alcohol.  He denies any illicit drug use except for smoking marijuana several times in the past.  He went camping in Vermont three weeks ago and travelled to Eastern Europe six months ago.  While in Eastern Europe he had several bouts of diarrhea.  He is sexually active with his girlfriend and uses condoms regularly.
His temperature is 36.7 C (98 F), blood pressure is 122/76 mmHg, and pulse is 98/min.  On physical examination, no murmurs are heard.  His abdomen is mildly tender without rebound.  Stool for occult blood is positive.  There are crops of purple non-blanching lesions affecting both thighs.  Neurologic examination is unremarkable.
Laboratory results are as follows:

Which of the following is most likely to establish this patient's diagnosis?

Quizplus · Accepted Answer

11ec193a_96b0_818f_853d_2d7155d51298_MD0002_00 This patient's presentation is most consistent with Henoch-Schönlein purpura (HSP), an immune-mediated vasculitis associated with immunoglobulin A (IgA) deposition. The classic features of HSP are summarized in the table above and include the classic tetrad of purpura, abdominal pain, arthritis, and glomerulonephritis. However, many patients do not have the full tetrad and the cause of HSP remains unknown. The characteristic finding of HSP is a leukocytoclastic vasculitis accompanied by IgA immune complexes within affected organs. Skin biopsies of purpuric lesions show small vessel involvement (primarily postcapillary venules) within the papillary dermis with an inflammatory infiltrate of neutrophils and monocytes. Adults with HSP have a higher risk of renal disease with development of end-stage renal disease (10-30% at 15 years of follow-up). In addition, intussusception commonly occurs in children with HSP but is rare in adults. (Choice A) Henoch-Schönlein purpura can present in adults with significant abdominal symptoms leading to acute abdomen (e.g., ischemic bowel). However, this patient's symptoms are fairly nonspecific and his stable examination and laboratory findings make acute abdomen less likely. (Choice B) Autoantibodies are negative in HS purpura. (Choice C) Blood smear is unlikely to give any clues given the normal cell lines and coagulation studies. (Choice D) Although this patient visited the New England area, Lyme disease typically presents with erythema migrans ("bull's-eye rash") rather than purpura and petechiae. Educational objective: Henoch-Schönlein purpura typically presents with lower extremity palpable purpura, nonspecific abdominal symptoms, renal disease, and arthritis/arthralgias. The diagnosis is suggested clinically, but tissue biopsy (e.g., skin, kidney) is the most sensitive and specific test to confirm the diagnosis. __________ References: The clinical implications of adult-onset henoch-schonelin purpura. (http://www.ncbi.nlm.nih.gov/pubmed/21619657) Henoch-Schönlein Purpura in adults: outcome and prognostic factors. (http://www.ncbi.nlm.nih.gov/pubmed/11961015)

A 20-Year-Old Man Is Brought to the Emergency Department Because