P030 A rash decision: refractory erythroderma as an atypical presentation of hypocomplementaemic urticarial vasculitis

Abstract

Hypocomplementaemic urticarial vasculitis is a rare immune-complex-mediated small-vessel vasculitis characterized by urticaria and hypocomplementaemia (low C4, C4 and/or C1q). It is usually associated with circulating anti-C1q autoantibodies. Diagnosis can be challenging due to variable clinical and histopathological features. We report the case of an 85-year-old man who presented with rapidly progressive, widespread erythroderma associated with severe pruritus and sleep disturbance. Examination revealed diffuse erythema with urticarial lesions affecting the trunk and limbs. Initial skin biopsies demonstrated mild acanthosis, spongiosis, hypogranulosis, focal parakeratosis and neutrophilic infiltration of the epidermis. This biopsy was thought to be in keeping with pustular drug reaction or psoriasis. Comprehensive medication review over the preceding 18 months failed to identify a culprit medication. In this context, he was commenced on treatment for psoriasis with acitretin 25 mg daily and weekly methotrexate, without clinical improvement. His rash continued to progress resulting in a further hospital presentation. Repeat biopsies during a second admission were interpreted as psoriasis with superimposed tinea incognito, prompting treatment with oral itraconazole. Given refractory disease, guselkumab was also commenced. Despite escalation of therapy, the patient did not respond, prompting further diagnostic review. With worsening of his skin condition this patient underwent a third set of biopsies. Repeat histological examination demonstrated features of acute small-vessel vasculitis with karyorrhectic debris, without psoriasiform changes. Clinicopathological correlation favoured a diagnosis of urticarial vasculitis. Complement studies showed hypocomplementemia (C3, 1.00 g L−1; C4, 0.06 g L−1) with normal C1q levels. Following multidisciplinary discussion, a diagnosis of hypocomplementaemic urticarial vasculitis was made. In terms of further management, the patient was commenced on dapsone, titrated to 100 mg daily, in combination with oral prednisolone 10 mg daily. This resulted in marked improvement in pruritus and gradual resolution of the cutaneous findings. Steroid-sparing strategies are ongoing, with omalizumab under consideration.