Cutaneous polyarteritis nodosa is a rare form of vasculitis relating to small-to-medium-sized arteries. Its etiology is unknown. Clinical manifestations include tender subcutaneous nodules, livedo reticularis, cutaneous ulcers and necrosis. Although it is distinct from systemic polyarteritris nodosa in that it lacks significant internal organ involvement, extra-cutaneous manifestations may be evident. Commonly encountered symptoms include fever, malaise, myalgias, arthralgias, and paresthesias. Exclusion of systemic polyarteritis nodosa is essential in diagnosis. The clinical course is chronic with remissions, relapses, and a favorable prognosis. Mild cases may resolve with nonsteroidal anti-inflammatory drugs. If more severe, treatment with systemic corticosteroids generally achieves adequate response; however, adjunctive therapy is often necessary to allow reduction in steroid dosage.

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Cutaneous involvement by myeloid leukemic cells is an unusual phenomenon. Clinical manifestations vary from erythematous papules to plum-colored plaques and nodules that may become purpuric and ulcerate. The definitive diagnosis of myeloid leukemia cutis requires the analysis of biopsy specimens using immunohistochemical staining to determine the expression of selective cell surface markers. We will review myeloid leukemia when first evident in the skin, particularly in the setting of myelodysplastic syndrome. The diagnosis of leukemia cutis in patients with myelodysplastic syndrome is indicative of concomitant or impending acute leukemic transformation. The early recognition and accurate identification of leukemic skin infiltrates in myelodysplastic patients is crucial, as this finding can have significant therapeutic and prognostic implications.