The aberrant activation of the complement paracrine pathway in DDD leads to the persistent degradation of C3 into C3a and C3b, a reduction in serum C3 levels, and the formation of membrane attack complexes that accumulate in the glomerular basement membrane, resulting in renal damage; moreover, the deposition of IgA immune complexes not only initiates the complement paracrine pathway but also activates the lectin pathway [10]. The gene discussed is C3; the disease is Dowling-Degos disease 1.