Hereditary C1 inhibitor deficiency associated with systemic lupus erythematosus.

Here, we report a family with two children (the elder son and younger daughter) diagnosed with juvenile-onset systemic lupus erythematosus (SLE) and the father diagnosed with hereditary angioedema. Serum C1 inhibitor (C1-INH) levels were low, and clinical exome next-generation sequencing detected a frameshift mutation in the gene in all three patients. The mother had neither of the clinical phenotypes. The son had cutaneous symptoms, fever and polyarthralgia, along with lupus nephritis, and thus required rituximab therapy as well as mycophenolate mofetil and low-dose steroids to control disease activity. The daughter had a milder disease, with cutaneous manifestation, fever and polyarthralgia, and which was controlled with mycophenolate mofetil, hydroxychloroquine and low-dose steroids. Both children had never experienced angioedema. The father had a long history of self-limiting, non-life-threatening irregular episodes of subcutaneous angioedema and abdomen pain. He was not on any regular medication for these symptoms. We searched the literature for evidence of hereditary C1-INH deficiency associated with monogenic SLE or SLE-like-phenotype.