[C1q nephropathy. Report of one case].

Clq nephropathy (Clq N) is an infrequent disease and only about 100 cases have been reported. It is defined by a pattern of immunofluorescence (IF) with dominant or co-dominant complement Clq with electron-dense deposits in the mesangium, without clinical or serological features of Lupus Nephritis. The most common histopathological findings of ClqN are focal segmental glomerulosclerosis and Minimal Change Disease. We report a 17 year-old male patient with an isolated selective proteinuria found in a routine study. He had normal renal function and urine culture was negative. Serum lipids, liver enzymes an complement were all normal. Serum antinuclear and anti-DNA antibodies, antineutrophil cytoplasmic antibodies (ANCA), HIV, Hepatitis B and C serology, were negative. Renal and abdominal ultrasonography was normal. The histopathological study revealed segmental glomerular sclerosis, moderate increase of mesangial matrix, Bowmann capsule adhesions and fucsinophil deposits in mesangium. The IF was positive (dominant) for Clq (+++) and IgA, IgG, IgM, C3++, all of them with a granular mesangial distribution. Ultrastructural findings were pedicelar effacement and paramesangial electron-dense deposits. Tubular reticular inclusions (TRI) were not found. Remission of proteinuria was reached after 18 months of treatment with enalapril and losartan. The patient remains with normal renal function. Clinical findings, negative serology for Lupus, light microscopy IF with dominant positivity for Clq, absence of TRI and paramesangial electron-dense deposits in electron microscopy lead us to the diagnosis of ClqN. A poor response to steroid therapy was described in ClqN. Thus it was worthwhile to differentiate it from lupus nephritis, that is responsive to steroids.