​Dermatology - Polyarteritis Nodosa

​Dermatology - Polyarteritis Nodosa 
Renal and visceral arteries are also affected by polyarteritis nodosa, a multisystem necrotizing vasculitis affecting the small and medium-sized muscle arteries. A rare variation of polyarteritis nodosa, cutaneous polyarteritis, is characterized by a skin- and occasionally peripheral nerve-limited vasculitis. About thirty percent of cases had hepatitis B involved.

Small- and medium-sized muscle arteries may develop necrotizing inflammation, which can then expand circumferentially to affect nearby veins. Patients exhibit painful skin lesions, fever, myalgia, and asthma. In addition to hypertension, the patients may experience mixed motor/sensory involvement with mononeuritis multiplex pattern, congestive heart failure, pericarditis, conduction system defects, myocardial infarction, cerebrovascular accident, nausea, vomiting, abdominal pain, ocular vasculitis, retinal artery aneurysm, optic disc edema, and renal failure.
Damage
Segmental lesions typically include bifurcations. Subcutaneous inflammatory nodules, measuring 0.5–2 cm, are bright red to bluish and run parallel to the affected artery. Livedo reticularis is present along with violaceous lesions that develop confluent to generate painful subcutaneous plaques. A cluster of nodular lesions is identified by a pathognomonic "starburst" livedo. Ischemia of nodules is followed by ulcers. Lesions typically affect both lower legs and thighs, but they can also occur in the arms, torso, head, neck, and buttocks. Days to months pass after the lesions disappear, leaving behind postinflammatory or violaceous hyperpigmentation.

The diagnosis is made clinically and verified by biopsy, which reveals polymorphonuclear neutrophils in the perivascular and muscular vessel wall layers as well as fibrinoid necrosis of the vessel wall with compromised lumen, thrombosis, and infarction of the tissues supplied by the involved vessel, either with or without hemorrhage.

Oral glucocorticoids are used as treatment: 1 mg/kg body weight of prednisone and 2 mg/kg of cyclophosphamide daily.