Two cases of polycystic kidneys in two siblings

Polycystic disease of the kidneys is a generalized lesion of characteristic clinico-pathological entity. It has two clincial forms: adult and infantile. The adult type is transmitted as a dominant disease where the latter is recessive trait. The infantile form had two pathological patterns. Form "A" in which the kidney is large and spongy, of normal shape and the cysts are numerous. Microscopically the connective tissue is not increased. The cysts are of equal size and shape. The nephrons are not reduced. In the form "B" the kidney may not have a normal shape and is not as large as the form "A". Microscopically the connective tissue is increased intensively. The cysts are of spherical shape and different sizes. The nephrons are reduced in number. We are reporting two cases of infantile polycystic kidneys in two siblings, one of whom represented form "A" and the other was similar to form "B". These two cases are interesting from the genetical point of view. We want to know whether the two forms are different manifestations of one disease with one genetic factor or they are two different diseases with two genetic factors? One can assume that the infantile polycystic kidney is a genetical disease with two different pathological manifestations or two different genetic disorders due to two different genetic factors.