Panniculitis in pediatric rheumatology practice: experience of a pediatric referral center

Introduction and Objectives: Panniculitis is a group of disorders characterized by inflammation of the subcutaneous adipose tissue. We aim to characterize patients with panniculitis monitored in a Pediatric Rheumatology Unit. Methods: Descriptive, cross-sectional, retrospective study, from January 2004 to December 2020. Demography, clinical characteristics, laboratory tests, skin biopsy and treatment were evaluated. Patients were divided into two groups: erythema nodosum (EN) and non-erythema nodosum (non-EN). Non-EN panniculitis was confirmed by histology. Exclusion criteria: atypical EN without a biopsy. Laboratory and clinical characteristics were compared. Results: Twenty-seven patients were enrolled (girls: 70%; median age of onset: 11 years). The main etiologies of EN (n = 19) were undetermined (37%), streptococcal infection (32%) and Crohn’s disease (11%). All patients with EN reported pain, 26% fever and 11% weight loss; 100% were treated with non-steroidal anti-inflammatory drugs (first-line therapy). Eight cases of non-EN panniculitis were included: lipoatrophic panniculitis (n = 3), lupus panniculitis (n = 2), cytophagic histiocytic panniculitis (n = 1 [CHP]), subcutaneous panniculitis-like T-cell lymphoma (n = 1; SPTCL), cutaneous polyarteritis nodosa (n = 1); 38% presented with nodules, 38% had fever and 38% had painful skin lesions. Seven non-EN panniculitis patients were initially treated with corticosteroids. The patients with CHP and SPTCL went into remission after immunosuppressive treatment and chemotherapy, respectively. The remaining patients were given immunomodulatory therapy. Patients with EN had more painful nodules and arthralgia/arthritis compared to non-EN patients. Discussion: New-onset constitutional symptoms during EN follow-up should prompt further investigation. Indurated and discolored nodules/plaques should evoke panniculitis. Histopathology can be helpful in non-EN panniculitis as it can guide towards specific diagnosis and appropriate treatment.