Multicystic renal dysplasia is a congenital dysplasia of the kidney characterized by large nonhomogeneous dilations of the collecting tubules. The dysplasias are usually unilateral, but it can be bilateral, segmental or focal, and the incidence is about 1 out of 5,000 to 10,000 births. There is a male predominance (ratio M2.4/F1) but females are twice as likely to have bilateral multicystic dysplastic kidney disease and associated non-renal abnormalities. Severe bilateral defects are lethal. Partial dysplastic involvement of both kidneys eventually leads to renal function impairment.
Mutations in TBX18 gene present on the long arm of chromosome 6 is known to be associated with multicystic renal dysplasia. A chromosome 19 breakpoint has also been observed in some patients with bilateral multicystic renal dysplasia, appearing to have occurred in intron 7 of the USF2 gene.