Acute renal failure in dense deposit disease: complete recovery after combination therapy with immunosuppressant and plasma exchange.

We describe the clinical course of a female adolescent who was followed because of isolated microhematuria and hypocomplementemia before admission to hospital with a sudden onset of acute renal failure. At presentation, she exhibited complement consumption through the complement alternative pathway (AP) while other serologic tests were negative. Renal biopsy revealed dense deposit disease (DDD) with a crescentic pattern. Intravenous methylprednisolone, followed by plasma exchange (PE), and intravenous cyclophosphamide pulses were started shortly after admission. C3NeF and anti-factor H antibody tests were negative. Serum factor H and I levels were normal as well as factor H activity. Screening for mutation in the factor H gene revealed the H402 allele variant. Clinical remission, defined as normalization in renal function and in the activity levels of the complement AP, was noted at one month post-presentation and throughout the follow-up. A repeat renal biopsy showed the disappearance of crescent formation, whereas electron microscopy revealed no regression in dense transformation of the lamina densa. In summary, our patient was successfully treated with immunosuppressant and PE. The absence of known factors associated with DDD suggests that, in this particular case, other regulatory mechanisms of complement AP might have been involved in the disease process.