Not all that is 'full house' is systemic lupus erythematosus: a case of membranous nephropathy due to syphilis infection

We describe an unusual case of membranous nephropathy precipitated by syphilis infection in a patient without systemic lupus erythematosus (SLE). A previously healthy 20-year-old man presented with leg and facial swelling. Laboratory investigation revealed nephrotic range proteinuria, acute kidney injury, hypocomplementaemia and a highly positive rapid plasma reagin. Kidney biopsy showed membranous nephropathy with 'full-house' immunofluorescence (IgG, IgA, IgM, C1q and C3), mimicking lupus nephritis class Vb. However, the patient had no features of SLE and had negative antinuclear and anti-double-stranded DNA antibodies. He was treated with high-dose methylprednisolone and mycophenolate mofetil for lupus nephritis and with penicillin for syphilis. After 2 months of therapy, his proteinuria resolved, and his renal function and C4 level normalised. This case illustrates that syphilis infection can be a mimicker of lupus nephritis. A literature review suggests that ful-house nephropathy may occur independently of lupus nephritis and may or may not develop into SLE.