Can Polyarteritis nodosa affect only one organ?
Yes. Localized PAN is uncommon but has been reported as an isolated finding in the skin, gallbladder, uterus, breast, appendix, and peripheral nerves. Cutaneous PAN is the most common presentation. Patients present with multiple, tender, nodular skin lesions (0.5–2 cm diameter) usually located on the legs and feet but can occur on arms and trunk. Diagnosis is confirmed by excisional (not punch) biopsy of a nodule. Livedo is found in 60%, and a mild polyneuropathy can be seen in 33%. Internal organ involvement is absent, but fever, myalgias, and arthralgias can be seen during the acute phase. Only 10% progress to systemic PAN in follow-up. Owing to the benign prognosis, patients can be treated with prednisone 20 to 40 mg/day with subsequent taper. However, relapses are common. Colchicine, dapsone, low-dose methotrexate, and azathioprine have been used successfully as steroid-sparing agents. Unlike in systemic PAN, CTX is rarely needed. In patients who develop cutaneous PAN after a streptococcal infection, antibiotic therapy may be an effective adjunctive therapy. Patients who develop localized PAN in organs other than the skin (e.g., gallbladder, uterus, and appendix) are typically cured by surgical excision. Therefore, immunosuppressive therapy is usually not needed. Patients, however, need to be followed to ensure additional organs do not become involved.
