Leukocytoclastic vasculitis as a rare dermatologic manifestation of Crohn's disease mimicking cellulitis: a case report

Background: Leukocytoclastic vasculitis (LCV) is an immune-complex mediated vasculitis characterized by neutrophilic inflammation and nuclear debris in post capillary venules. LCV is a rare dermatologic manifestation of Crohn's disease (CD) and may occur with the onset of the disease or any time after the diagnosis including the period of exacerbation.

Case presentation: We present a 70 year old woman with history of psoriasis and treatment refractory CD requiring monoclonal antibody therapy with ustekinumab. One month prior to the current admission, she developed abdominal pain, worsening diarrhea and was diagnosed with CD exacerbation for which she was given ustekinumab. While her abdominal symptoms mildly improved with ustekinumab, she developed new bilateral lower extremity rash initially treated with levofloxacin for presumed cellulitis. The rash consisted of mild erythematous, non-scaling patches with scattered non-palpable petechiae on the lower extremities with subsequent involvement of abdomen, lower back and buttocks. Abdominal exam showed diffuse tenderness without mass, guarding or rebound while reminder of physical exam was unremarkable. Following the failure of antimicrobial therapy, she was diagnosed with LCV by skin biopsy. Complete work up was negative for infectious, malignant and inflammatory etiologies of LCV. Patient improved with increased dose of budesonide and subsequently continued to tolerate ustekinumab without recurrence of LCV.

Discussion and conclusion: LCV is a rare form of vasculitis and one of the rarest dermatologic manifestations of CD, appearing at any stage of the disease. LCV has been associated with autoimmune diseases, infections, specific drugs (levofloxacin, ustekinumab), and malignancy. Clinical presentation of LCV is variable and frequently mistaken for cellulitis. LCV should be considered in differential diagnosis of bilateral lower extremity rash in patients with CD after infectious, malignant and auto-immune/inflammatory etiologies are excluded. Unlike erythema nodosum (EN) and pyoderma gangrenosum (PG), LCV requires biopsy for diagnosis. Most patients respond well to steroids without scarring.

Keywords: Case report; Cellulitis; Crohn’s disease; Dermatologic manifestation; Inflammatory bowel disease; Leukocytoclastic vasculitis; Levofloxacin; Ustekinumab.