Erythrodermic pustular psoriasis triggered by intravesical bacillus Calmette-Guérin immunotherapy

Conflict of interest: none declared. An 80‐year‐old man was diagnosed with bladder carcinoma in situ and underwent intravesical BCG (bacillus Calmette‐Guérin) immunotherapy. The treatment involved weekly instillation of BCG (ImmuCyst®; Alliance Pharmaceuticals, Chippenham, Wiltshire, UK), 81 mg into the bladder over 6 weeks. After the sixth BCG treatment, the patient developed fever, malaise and weight loss. Computed tomography showed multiple pulmonary nodules with a miliary appearance. A transbronchial biopsy was performed, which revealed noncaseating granulomas. A diagnosis of pulmonary BCGosis was made, which is a disseminated BCG infection and a rare complication of intravesical BCG immunotherapy. The patient was started on empirical antituberculous treatment consisting of rifampicin, isoniazid and ethambutol. Four days into treatment, he developed a seborrhoeic dermatitis‐like eruption involving the face. Over the subsequent 2 weeks, the skin eruption continued to evolve in a cephalocaudal manner, leading to a temporary pause in the antituberculous treatment. At this stage, the clinical appearance was that of pityriasis rubra pilaris (PRP), with confluent scaly erythema, keratotic follicular papules, islands of sparing and palmoplantar keratoderma (Fig. 1a–c). The histological findings, of alternating bands of parakeratosis and orthokeratosis with follicular plugging, supported the clinical diagnosis (Fig. 1d).