C1q nephropathy and isolated CD59 deficiency manifesting as necrotizing crescentic glomerulonephritis: A rare association of two diseases.

C1q nephropathy is a recently described clinico-pathologic entity with a variable clinical presentation and pathology. Crescentic glomerulonephritis (GN) has been reported in only two patients in the available literature. CD59 deficiency, along with lack of CD55, is responsible for paroxysmal nocturnal hemoglobinuria (PNH). Few cases of isolated CD59 deficiency have been described with PNH-like features. A middle-aged adult male presented with rapidly progressive renal failure. Serological investigations were negative. A renal biopsy revealed necrotizing crescentic GN with rupture of Bowman's capsule. Immunofluorescence on the frozen sections showed dominant mesangial deposits of C1q along with IgM. Hematological work-up of the patient revealed isolated CD59 deficiency. Hence, a final diagnosis of C1q nephropathy and CD59 deficiency manifesting as crescentic GN and hemolytic anemia was made. The co-existence of two rare disorders, C1q nephropathy and CD59 deficiency, in a patient with necrotizing crescentic GN is described for the first time to the best of our knowledge. The pathogenetic link of these two entities with the clinical manifestation requires further study.