Erysipelas-like Erythema: A Pathognomonic Rash in Children with Familial Mediterranean Fever

Objective: Familial Mediterranean fever (FMF) is the most common genetic autoinflammatory disease presenting as recurrent fever episodes, and inflammation of serosal surfaces, joints, and skin. During attacks, erysipelas-like erythema (ELE) may occur on the dorsum of the foot, ankle, or lower leg. Although the skin involvement is less common, ELE is pathognomonic. We aimed to review the frequency and characteristics of ELE in children diagnosed with FMF and to identify genotypic and phenotypic differences between patients with and without ELE, if any.Methods: This study included children aged 0-18 years diagnosed with FMF followed up by two tertiary pediatric rheumatology units. The data were collected by two pediatric rheumatology fellows from the patients' files and electronic records. We divided the cohort into two groups according to whether they had ELE. Those with ELE were included in group 1 and those without ELE were in group 2.Results: Two thousand-three patients participated in the study. There were 197 (9.8%) patients with ELE in group 1 and 1806 (90.1%) patients without ELE in group 2. The mean age of onset of symptoms in group 1 was significantly lower than in group 2 [4.85 (minimum-maximum: 0.1-17) vs. 5.98 (minimum-maximum: 0.1-17) years, p<0.001]. The median age at diagnosis was significantly higher in group 1 [8 (0.6-18) vs. 6 (0.5-18) p<0.001]. The diagnostic delay time was 24 months in group 1, 13 months in group 2, and the duration was significantly longer in group 1 [24 (0-150) vs. 13 (0-192) p<0.001]. M694V homozygosity was more frequent in group 1 [n=116 (58.9%), n=484 (26.8%), p<0.001].Conclusion: Because ELE is an uncommon clinical presentation, clinicians should be alert. The clinical course of patients presenting with ELE may have a more severe disease course.