Cutaneous diphtheria from 2018 to 2022: an observational, retrospective study of epidemiological, microbiological, clinical, and therapeutic characteristics in metropolitan France

The incidence of diphtheria has been rising over the past decade, particularly in its cutaneous form. A clinical review of the case series was therefore required. We reviewed the epidemiological, clinical, microbiological and therapeutic data of cutaneous diphtheria cases, in adult patients living in metropolitan France with a skin sample positive for corynebacteria of the <i>diphtheriae</i> complex between 2018 and 2022. Of the 132 cases identified, 63 met the inclusion criteria. The mean age was 53.8 years, 68.3% were men and 56.7% had travelled outside mainland France. Immunization rate was 44%. Lesions involved the lower limbs (86.9%), corresponded to ulcerations in 82% of cases. Two species were identified in the study: <i>C. diphtheriae</i> (77%) and <i>C. ulcerans</i> (23%). 39% were toxigenic. Other bacteria were present in 88.9% of cases: <i>Staphylococcus aureus</i> (54.7%) and <i>Streptococcus pyogenes</i> (49.1%). 17.5% of clinicians ignored the presence of Corynebacteria of the <i>diphtheriae</i> species complex. Clinicians seem to be unfamiliar with this disease due to under-reporting and a lack of knowledge and awareness among clinicians, and rarely mention it, which explains the frequent failure to comply with French recommendations. Clinical data are consistent with the literature. Continued epidemiological surveillance, increased vaccination coverage in high-risk populations and better information of clinicians are essential to prevent and control this preventable disease.