An 8-month-old male infant presents with progressive renal and hepatic failure. Despite intensive medical therapy, the infant dies. At the time of autopsy, the external surfaces of his kidneys are found to be smooth, but cut section reveals numerous cysts that are lined up in a row. What is the mode of inheritance of this renal abnormality?

) Cystic diseases of the kidney, which may be congenital, acquired, or inherited, have characteristic gross appearances. In two types of cystic renal disease, the numerous cysts are found in both the coex and medulla. These two types of polycystic disease of the kidney are the infantile type and the adult type. Adult polycystic kidney disease typically presents in adulthood and has an autosomal dominant inheritance pattern. Histologically, the cysts are lined by tubular epithelium, while the stroma between the cysts is normal. Adult polycystic renal disease is associated with liver cysts and berry aneurysms, which may rupture and cause a subarachnoid hemorrhage. About one-half of patients with adult polycystic renal disease eventually develop uremia. Infantile polycystic kidney disease typically presents in newborns, has an autosomal recessive pattern of inheritance, and is associated with hepatic cysts (microhamaomas) and congenital hepatic fibrosis. Grossly, these renal cysts have a radial spoke arrangement In two types of cystic renal disease, the cysts are limited to the medulla. Medullary sponge kidney is usually asymptomatic, is not familial, and is characterized by normal-sized kidneys with small cysts in the renal papillae. In medullary cystic disease complex (nephronophthisis), kidneys are small and sclerotic with multiple cysts at the coicomedullary junction. Individuals with this abnormality present in the first two decades of life with salt-wasting polyuria and progressive renal failure. Most cases are familial and display both recessive and dominant inheritance patterns. Two other types of cysts that are not limited to the medulla are simple cysts and acquired cysts. Simple coical cysts are single, unilateral cysts, found in adults, that are benign. Patients are usually asymptomatic, but they may present with microscopic hematuria. Acquired polycystic renal disease is associated with chronic renal dialysis. These kidneys are shrunken and have multiple cysts and an irregular surface. Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition