Drug-induced bullous pemphigoid

Bullous pemphigoid during cancer immunotheraphy with PD-1 checkpoint inhibitor 

Symptoms/ signs

87-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 photographs

Clinical presentation

Physical 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 history

He 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 tests

Based 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 disease

In 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.