63 | diffuse erythroderma in a complex geriatric patient: A diagnostic and therapeutic challenge

We describe the case of a 71-year-old man with diabetes, hypertension, and metastatic lung cancer who was being treated with pembrolizumab (anti-PD-L1). He was initially referred for consultation due to the onset of a dermatological presentation characterized by urticarial plaques and intensely pruritic bullous lesions, strongly suggestive of bullous pemphigoid (BP). Since laboratory tests (histological examination with immunofluorescence and ELISA) confirmed the suspected diagnosis of BP, pembrolizumab—the presumed iatrogenic cause of the condition—was discontinued in consultation with the oncology team, and systemic therapy with deflazacort and dapsone was initiated, resulting in clinical improvement and remission of the bullous manifestations. However, during follow-up, after tapering the treatment, a generalized erythrodermic condition developed, accompanied by furfuraceous desquamation. When a paraneoplastic origin was suspected, a new skin biopsy was performed; the findings (histopathological examination with immunofluorescence) confirmed the diagnosis of erythrodermic pemphigoid. The patient was therefore started on oral erythromycin therapy (1.5 g/day), which, in combination with tapering doses of deflazacort, ultimately led to complete clinical remission. In addition to the classic presentation, pemphigoid (PB) can present in various atypical forms, including localized and non-bullous variants. Among these, erythrodermic pemphigoid represents a rare and difficult-to-diagnose manifestation that can mimic inflammatory or paraneoplastic erythroderma. We considered the case in question worthy of mention because it offers multiple and interesting points for discussion, pertaining not only to the rarity of the clinical variant of erythrodermic pemphigoid but also to the possible triggering role of anti-PDL1 agents in this specific case, as well as the challenges generally associated with the therapeutic approach in patients with fragile pemphigoid and multiple comorbidities. In this regard, we highlight the excellent results achieved with the use of erythromycin, an older but well-tolerated antibiotic with anti-inflammatory and immunomodulatory properties that, in our case, proved decisive.