Comorbidities of pyoderma gangrenosum: a retrospective multicentric analysis of 126 patients

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Dear Editor, Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis with challenging diagnosis and unclear underlying mechanisms. Multifactorial causes are purposed, including neutrophilic dysfunction, aberrant cellular immunity and cytokine activities and genetic predisposition.1 An association with a systemic disease is classically described in 25–75% of cases, including inflammatory bowel disease (IBD), inflammatory rheumatological diseases (IRD) and haematological disorders. An association of PG with cardiovascular disorders has also been proposed.2,3 Due to its rarity, the literature on PG‐associated comorbidities remains limited to date. Therefore, the aim of our multicentre study was to describe the epidemiology of PG in French dermatological wound care centres, focusing on clinical characteristics, demographics and comorbidities. We conducted a retrospective multicentre study from January 2000 to December 2015. Data were obtained from the medical records of nine specialized dermatological wound care centres in France, members of the Angiodermatological Group of the French Society of Dermatology (SFD). The inclusion criteria were based on the modified main and additional diagnostic criteria for PG. The main diagnostic criteria included the presence of a compatible clinical aspect of PG, and the exclusion of other differential diagnoses. Two additional criteria were also required, including compatible histology, existence of relevant associated concomitant diseases, response to systemic immunosuppressive therapy, pathergy phenomenon and painful ulcers. Selected experts from each dermatological centre validated each patient inclusion. Clinical data was recorded from the patient's medical files retrospectively. Statistical analysis was performed with Statistical Package for Social Sciences (IBM SPSS Inc.), Statistics and Stata software. A P‐value < 0·05 was considered significant. A total of 126 patients with PG were included. The M : F sex ratio was 0·38 with 35 (27·8%) men and 91 (72·2%) women. The mean age was 59 ± 23 (range 11–99) years. Women were significantly older than men with a mean age of 62 ± 24 years compared with 51 ± 20 years (P =0·02). Lesion distribution was multifocal in 60·5% of patients. Ulceration was the most frequent aspect of PG (93·0%), while pustular PG and superficial PG were reported in 10·5% and 3·5% of cases, respectively. Injuries mainly affected the lower extremity in 83·3%. Pathergy was found in 28·1% of cases. Patients who developed pustular or superficial PG were significantly younger than patients with ulcerations, with a mean age of 39 ± 18 vs. 60 ± 23 years (P =0·01). The potentially relevant cofactors of patients with PG according to sex are summarized in Table 1. Overall, 67 (53·2%) of 126 patients with PG had a classically associated disease, including IBD in 23·8%, IRD in 7·1% and haematological disorders in 24·6% of cases. Crohn disease was predominately found in women (19·8% of cases among women vs. 2·9% of cases among men, P =0·02). The mean age of patients with PG with haematological disorders was significantly higher compared with the rest of the group: 72 ± 16 years vs. 57 ± 23 (P <0·001). On the contrary, patients with IBD were significantly younger than the rest of the population, with a mean age of 46 ± 20 years vs. 63 ± 23 (P <0·001). Potentially relevant cofactors of patients with pyoderma gangrenosum according to sex IBD, inflammatory bowel disease; IRD, inflammatory rheumatological disease Potentially relevant cofactors of patients with pyoderma gangrenosum according to sex IBD, inflammatory bowel disease; IRD, inflammatory rheumatological disease Diabetes mellitus was found in 15·1% of cases, and arterial hypertension in 36·5%. Obesity was found in 18·8% (missing data in 62 cases). To our knowledge, our study is the fourth‐largest international series and the largest French series.2,3,4,5 This study confirms, as previously described, the female predominance of PG and the average age of around 60 years. Our results suggest that PG should be ruled out in young patients presenting atypical lesions as pustular and superficial forms. We found a high proportion of classically associated diseases suggesting that, regardless of age or sex, classical comorbidities will be associated to PG in half of the cases. IBD especially concerns young patients, whereas haematological disorders concern older patients. As previously described, our data showed higher prevalence of cardiovascular diseases, and especially diabetes as potential comorbidities.6 Recently, it has been hypothesized that PG is a systemic immune‐mediated inflammatory disease rather than a purely skin disease.7 In fact, the physiopathology of both PG and associated cardiovascular diseases implies an increase in the inflammatory response and in the production of some interleukines, particularly through T‐helper 17 cells.8 In this context, cardiovascular diseases should be potential comorbidities of PG, and should be ruled out in patients with PG, especially when corticosteroid treatment is needed. In order to contribute to the understanding of PG, further studies are required to reach definitive conclusions about the physiopathological associations between PG and comorbidities.

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