Subcutaneous granuloma annulare: a systematic review of a rare and underdiagnosed disease

Subcutaneous granuloma annulare (SGA) is a rare clinicopathologic subtype of granuloma annulare characterized by the presence of subcutaneous nodules. There are no present reviews synthesizing the clinical features and treatment modalities in SGA. We conducted a systematic review following PRISMA guidelines [CRD42022344672] on all peer-reviewed English-language studies that reported one or more cases of SGA. A total of 97 studies, comprising 26 case series and 71 case reports with 324 patients, were included for analysis. Most cases were predominantly pediatric, with 78.9% of the cases identified being age 16 or lower and a median age of diagnosis of 6. There was no overall gender predisposition. Although over two-thirds of patients did not have any comorbidities, diabetes mellitus was the most common comorbidity present in 4% of cases. The most common feature of SGA was nodules, which were present in 99.6% of patients. Pain or tenderness was reported in 15.4%, and erythema of overlying skin in 11.0% of cases. Surgical excision was performed in 96/141 (68.1%) patients. Among the 27/141 (18.0%) patients who were conservatively managed, 87.0% spontaneously improved, including 60.0% who completely self-resolved. Topical and intralesional steroids were used in 3.40% and 1.85% of patients, respectively, resulting in complete or partial resolution in 54.6% and 100%. Among patients who were followed up, 83/324 (25.6%) patients experienced recurrence after a median duration of 26 weeks. SGA is predominantly a pediatric disease that frequently occurs on the limbs and the head. Juxta-articular lesions are more commonly observed in adults than in children. Surgical excision is common and effective in most patients. Spontaneous improvement occurs in most untreated cases, and intralesional steroids but not topical steroids may be beneficial for non-resolving cases and to reduce time to resolution.