Today we discussed an interesting case of a 21 year old male with a non-healing ulcer on his shin. Interestingly he had been recently diagnosed with ulcerative colitis. While, the diagnosis of pyoderma gangrenosum seemed most obvious, the biopsy in fact showed evidence of leukocytoclastic vasculitis and the patient was found to have high peripheral eosinophils and was P-ANCA positive. Talk about a curve ball!

Here are some interesting questions that arose from our discussion:

1) Differential Diagnosis of ulcerative lesion:
Refer to the following NEJM article for an interesting discussion of skin ulcers misdiagnosed as pyoderma gangrenosum. This article gives a great differential diagnosis for ulcerative skin lesions. The key is to have a broad differential and to do a biopsy! The treatment for pyoderma gangrenosum is not benign (steroids and other immunosuppressants) so be sure of the diagnosis before you treat.

2) Leukocytoclastic vasculitis is not a diagnosis in and of itself but a pathologic term describing neutrophilic small vessel vasculitis. It is an indication of small-vessel vasculitis. This can occur in the following settings:

• ANCA associated small vessel vasculitis:  
• Granulomatosis with polyangiitis (formerly known as Wegener's vasculitis)
• Churg-Strauss vasculitis
• Microscopic Polyangiitis
• Immune Complex associated small vessel vasculitis:
• Hepatitis C with cryoglobulinemia
• Henoch-Schonlein pupura (HSP)
• Connective tissue disease-associated vasculitis:
• RA
• SLE
• Sjogren's Syndrome
• Endocarditis
• Hypersensitivy vasculitis:
• Penicillin, ASA, amphetamines, thiazides
• Viral infections:
• Strep throat
• bacterial endocarditis
• TB
• hepatitis
• Staphylococcal infections
• Foreign proteins (serum sickness)

3) Differential for non-vasculitic P-ANCA positivity:

• Infectious: HIV, mycobacterial infections, severe pneumonia, bacterial endocarditis
• Chronic: Rheumaotid arthritis, IBD, Sweet's syndrome, eosinophilia-myalgia syndrome, Goodpasture's syndrome
• Neoplasms: Atrial myxoma, small cell lung cancer, NHL, myelodysplasia, colon carcinoma

See ANCA in diseases other than systemic vasculitis

4) Differential for Eosinophillia:

• Infectious: Parasitic infection, fungal infection (aspergillosis)
• Hematologic/neoplastic: Hypereosinophilic syndromes, leukemia, lymphoma
• Allergic disorders: atopic dermatitis, asthma, rhinitis, medications
• Rheumatic disease: Churg Strauss
• Miscellaneous: Adrenal insufficiency, cholesterol embolization