Drug-induced bullous pemphigoidBullous pemphigoid during cancer immunotheraphy with PD-1 checkpoint inhibitor Symptoms/ signs87-year-old male patient.The subject came to our attention complaining of intense and widespread itching for 2 months, unresponsive to standard doses of antihistamine therapy.Patient photographsClinical presentationPhysical examination of the entire skin area showed eczematous patches on both arms and thighs, scalp and back. On the inner surface of the left thigh, there was a blister on erythematous skin, characterised by serous content and a taut head. Finally, careful examination of the mouth revealed erosions on the inner mucosa of the upper lip.Medical historyHe was diagnosed with metastatic squamous cell lung cancer (stage IVB) with high tumour expression of PD-L1 ligand > 50% and no positivity for EGFR or ALK. Therefore, in July 2022, cancer immunotherapy was initiated with pembrolizumab, an anti-PD-1 monoclonal antibody.Differential diagnosis Urticaria Drug-induced rash – bullous variant Autoimmune bullous disease Diagnostic testsBased on a suggestive clinical presentation, the diagnosis is supported by a compatible histology and confirmatory direct immunofluorescence. Although the latter test is the gold standard for diagnosing bullous pemphigoid, in the current laboratory-based approach, the detection of pathogenic autoantibodies by direct immunofluorescence and ELISA can be considered sufficient. Furthermore, the detection of specific anti-BP180 or anti-BP230 autoantibodies allows other autoimmune bullous diseases to be ruled out.Description of the diseaseIn predisposed individuals – i.e., those with a genetic susceptibility in terms of immunological response or antigenic properties of the dermo-epidermal junction – exposure to systemic drugs may be a trigger factor for bullous pemphigoid. The start of medication may precede the onset of the disease by up to three months. With bullous pemphigoid, the mouth is affected in 10 to 30 per cent of patients.Pharmacological treatment and patient instructionsOral corticosteroid therapy was prescribed with prednisone 25 mg ½ tablet after breakfast and, for the management of itching, antihistamine therapy with desloratadine 5 mg 1 tablet twice daily.Topical steroids were also applied locally to lesions on the body, particularly on the scalp.Dermocosmetic management  LIPIKAR Baume AP+M, a lipid-replenishing and anti-itching body balm that restores the balance of the skin’s microbiome, for local use twice daily. Follow-up (adjuvant treatment outcomes)At the clinical check-up after 6 weeks of therapy, the patient showed excellent clinical control of the condition and relief from itching, so the oral corticosteroid therapy was slowly scaled back. The patient was instructed to apply topical steroids reactively, in the event of new lesions appearing and a body balm. Protecting the integrity of the skin barrier is essential in elderly patients, as the processes associated with skin ageing compromise the function and mechanical strength of the skin and can predispose them to the onset of bullous lesions.
