A 58-year-old woman was admitted due to a pseudomembranous pharyngitis. The 
patient had not been vaccinated against diphtheria. Corynebacterium ulcerans was 
cultured from a throat swab. The production of diphtheria toxin by these 
bacteria was demonstrated with PCR and an immunoprecipitation test. The patient 
was cared for in respiratory isolation and was treated with benzylpenicillin. 
She quickly recovered and was discharged four days after admission. A contact 
investigation did not reveal any dissemination of the toxin-producing C. 
ulcerans and a source was not found. In spite of the large-scale vaccination 
against diphtheria which has taken place in the Netherlands since 1953, a 
physician has to consider diphtheria in the differential diagnosis of patients 
who present with a clinical syndrome compatible with this disease. Either 
Corynebacterium diphtheriae or C. ulcerans could be the pathogen responsible.