Crohn’s disease diagnosis can prove elusive and may also be subject to overdiagnosis, especially when considering the relatively inaccessible small intestine. An increasingly sophisticated armamentarium of imaging modalities (eg, capsule endoscopy) and laboratory tests (eg, inflammatory bowel disease serologies) may lure clinicians into a diagnosis of Crohn’s disease that is unwarranted. The report by Sanft and associates is such an example.
HSP is an IgA-mediated, small-vessel vasculitis that often presents with purpuric rash, abdominal pain, kidney involvement, and arthritis. Common gastrointestinal (GI) symptoms are colicky abdominal pain, nausea, vomiting, hematemesis, hematochezia, and diarrhea. Intestinal perforation, intussusception, ischemia, and necrosis are rare complications of HSP. HSP-associated vasculitis can affect any part of the gastrointestinal tract.
It is true that gastrointestinal symptoms generally occur with associated systemic involvement of the skin, joints, or kidney. There have been several reports in which gastrointestinal symptoms preceded other systemic symptoms. Involvement of the terminal ileum has led to the diagnosis of Crohn’s disease in these cases.
These patients typically present with gastrointestinal symptoms at least 4 weeks before the purpuric rash. In the absence of any other systemic symptoms, midileal inflammation as detected by CT scan suggests the diagnosis of Crohn’s disease. At this point, treatment with steroids for this presumptive diagnosis seems appropriate. Subsequent development of purpuric rash, when viewed through the diagnostic prism of Crohn’s disease, appears to be an associated complication, Sweet syndrome. Again, with the diagnosis of Crohn’s disease assumed well-established, the endoscopic and histologic changes in the terminal ileum are made to fit, even though the presence of hemorrhagic necrosis on histology is not a common finding of Crohn’s disease. However, given this presentation, and improvement of symptoms with prednisone, it is easy to conclude that the patient has Crohn’s disease.
These inconsistencies are easily detected after the correct diagnosis of HSP is confirmed by renal biopsy. Indeed this case, as Sanft and associates report, “highlights both the broad differential diagnosis of ileitis and the importance of this uncommon presentation of HSP.” However, atypical presentations can be misleading and in some cases only manifestations brought on by the passage of time can lead to the right diagnosis.