Successful Anifrolumab Treatment for Refractory Skin Lesions in Monogenic Lupus Due to C1R Deficiency

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease exhibiting clinical heterogeneity among affected individuals. In monogenic lupus, which results from single-gene mutations, there is an early onset, atypical and severe course, and usually a familial predisposition. One of the common causes of monogenic SLE is deficiencies in the early components of the classical pathway of the complement system. We present here a 9-year-old male with hereditary C1R deficiency, suffering from chronic discoid rash since the age of 18 months, who did not sufficiently respond to conventional treatment, including topical and systemic steroids, hydroxychloroquine, mycophenolate mofetil, intravenous immunoglobulin, and baricitinib. Subsequently, the skin findings improved after the initiation of anifrolumab, an anti-IFNAR antibody. To the best of our knowledge, this report represents the first successful treatment of monogenic lupus and C1R deficiency with anifrolumab in the literature.