Complement-4 deficiency in a child with systemic lupus erythematosus presenting with standard treatment-resistant severe skin lesion.

The complement system is of great importance in systemic lupus erythematosus. Complete genetically determined deficiencies are with few exceptions reported for the various complement proteins, and most of the deficiency states are rare. Deficiencies of the factors in the classical pathway are also associated with development SLE and SLE-like disorders. Most of the patients with lupus present skin involvement. Approximately, 75-95% of patients with cutaneous lupus erythematosus respond to antimalarial therapy and/or topical glucocorticosteroids. Immunosuppressive agents are usually considered a second-line approach in patients with resistant disease. In this study, we present the clinical features and determine the molecular basis responsible for the complete C4A and C4B deficiencies in a lupus patient presented subacute cutaneous lupus erythematosus and resistance to treatment.