The PARACELSUS score: a novel diagnostic tool for pyoderma gangrenosum.

BACKGROUND: The lack of objective diagnostic criteria renders pyoderma gangrenosum (PG) a diagnosis of exclusion. The diagnostic approaches proposed to date have not been systematically evaluated. Thus, PG remains a challenging and frequently misdiagnosed disorder. OBJECTIVES: To develop and assess a comprehensive, yet clinically practicable, sensitive diagnostic scoring system for PG. METHODS: Clinical history and images of a total of 60 participants with previously confirmed PG located on the lower extremity and a control cohort of 50 patients with venous leg ulcers were retrospectively evaluated by expert teams at two tertiary dermatological centres specializing in wound care using a newly developed diagnostic scoring system composed of 10 criteria. RESULTS: The three major diagnostic criteria are rapidly progressing disease, assessment of relevant differential diagnoses and a reddish-violaceous wound border (prevalent in 98% of patients with PG). Minor criteria (evident in 61-95% of patients with PG) include amelioration by immunosuppressant drugs, characteristically irregular shape of ulceration, extreme pain > 4/10 on a visual analogue scale and localization of lesion at the site of the trauma. Three additional criteria (observed in up to 60% of patients with PG) encompass suppurative inflammation in histopathology, undermined wound borders and systemic disease associated. A total score value of 10 points or higher indicates a high likelihood of PG and differentiates PG from venous leg ulcers. The initial letters of the above-listed criteria form the acronym PARACELSUS. CONCLUSIONS: The PARACELSUS score represents a novel, easily implementable, effective and sensitive diagnostic tool for PG.