A five year old girls presents with fever and conjunctivitis. Physical examination is significant for oral erythema and fissuring along with a generalised maculopapular rash and cervical lymphadenopathy. What is the most likely diagnosis?

Polyaeritis nodosa has a peak incidence between the ages of 40 and 50, with a male-to-female ratio of 2 : 1. The annual incidence is about 2/1 000 000. Hepatitis B is an impoant risk factor and the incidence is 10 times higher in the Inuit of Alaska, in whom hepatitis B infection is endemic. Presentation is with fever, myalgia, ahralgia and weight loss, in combination with manifestations of multisystem disease. The most common skin lesions are palpable purpura , ulceration, infarction and livedo reticularis . Pathological changes comprise necrotising inflammation and vessel occlusion, and in 70% of patients aeritis of the vasa nervorum leads to neuropathy, which is typically symmetrical and affects both sensory and motor function. Severe hypeension and/or renal impairment may occur due to multiple renal infarctions but glomerulonephritis is rare (in contrast to microscopic polyangiitis). The diagnosis is confirmed by conventional or magnetic resonance angiography, which shows multiple aneurysms and smooth narrowing of mesenteric, hepatic or renal systems, or by muscle or sural nerve biopsy, which reveals the histological changes described above. Treatment is with high-dose glucocoicoids and immunosuppressants, as described for ANCA-associated vasculitis . Ref - HArrisons 20e p2582 , Davidsons 23e p1042