Thanks to Dr. Fleming for presenting an interesting case of cutaneous polyarteriitis nodosa which started as distal peripheral neuropathy.
Cutaneous PAN is a rare form of PAN. There is a slight female predominance (1:1.7) with an average age of diagnosis 43.5years. The etiology is generally unknown. However, it may reflect underlying disease, infection of medication use. Individuals with CPAN should be evaluated for: antecedent Group A beta hemolytic strep infection (check an ASO), hepatitis B, hepatitis C, parvovirus, mycobacterium TB, IBD, minocyline use.
Diagnosis requires pathologic correlation with clinical findings. Histologically there is small/medium artery vasculitis clinically presenting as tender subcutaneous nodules on the lower extremities, often with livedo reticularious and cutaneous ulceration. There are no specific serologic tests.
CPAN is described as a chronic, relapsing and remitting course. Treatment is less aggressive than PAN. Mild cases responds to NSAIDs and topical corticosteroids. More refractory cases require corticosteroids and immunomodulators indlucing hydroxychloroquine, azathioprine, dapsone, cyclophosphamide, methotrexate and IVIG. The prognosis is good without any known mortality for CPAN itself. However, there is a potential for progression to PAN. One study notes 2 out of 20 patients with CPAN developed PAN after 18 and 19 years of follow-up.
For additional reading, please refer to Morgan AJ et.al. Review: Cutaneous polyarteritis nodosa. Int J Dermatol. 2010 Jul; 49(7):750-6.