Medullary cystic disease complex
Medullary cystic disease complex is a group of hereditary tubulointerstitial diseases that shares cyst formation at the corticomedullary junction of the kidney and includes diseases with various clinical features, different modes of inheritance, and associations with extrarenal disorders.
In 1951, the disease was first described as a hereditary disorder progressing into renal failure before puberty. Although not mentioned, medullary cysts were present in one of the micrographs. It was not until the 90th that the group could be definitely classified based on molecular genetic data.
By the type of inheritance we distinguish the autosomal recessive nephronophthisis and autosomal dominant medullary cystic kidney disease.
Nephronophthisis may be divided clinically into juvenile (median age at onset, 13 yr), infantile (median age at onset, 1 to 3yr), and adolescent (median age at onset, 19 yr) forms. The two types of medullary cystic kidney disease also differ by median age at onset, which is in type 1 62 years and type 2 32 years.
Nephronophthisis types 1 through 6 indicate different genes involved in pathogenesis. Juvenile form is cause by type 1 and 4, infantile by type 2, and adolescent type 3.
The clinical diagnosis is made by family history and renal symptoms. Sometimes extrarenal manifestations underpin the diagnosis. If available histomorphology provides further evidence. As cysts develop late in disease, typical pathomorphological findings, cysts restricted to the renal medulla or corticomedullary border, appear late in ultrasonography, CT, and MRI, too. Early signs are rather unspecific such as small kidneys and loss of corticomedullary differentiation. Molecular genetic testing, where available, provides a better early diagnosis.
Medullary sponge kidney is an important differential. This benign disease does not show progressive renal failure.
All genes involved in pathogenesis of cystic kidney diseases affect tubular ciliary function. The exact mechanism by which ciliary dysfunction results in cyst formation remains to be elucidated.
Alexander F et al. (1970) Familial uremic medullary cystic disease.[^]