prostate hypoplasia prostate hypoplasia prostate hypoplasia is the congenital abnormality of a small (or absent) prostate gland. often associated with other abnormalities of the urogenital system. often due to abnormality in mesenchymal cells and associated with prune belly syndrome. observed in 5α-reductase 2 deficiency in which impaired 5α-dihydrotestosterone (dht) synthesis impairs prostate development which is dht dependent.