Kidney Involvement
Tuberous Sclerosis Complex (TSC) can present itself as five different lesions in the kidneys: angiomyolipomas, cysts, malignant angiomyolipomas, oncocytomas, and renal cell carcinoma.
Benign angiomyolipomas are the most common TSC lesion, occurring in 70 percent to 80 percent of adults and older children. Accurate noninvasive ultrasound, CT, or MRI diagnosis of these lesions is highly dependent on their fat content. It can sometimes be difficult to tell the difference between a small or low-fat-content benign angiomyolipoma and a malignant tumor.
When tumors become larger than 4 cm, bleeding of the angiomyolipoma, the primary complication of this lesion, increases in frequency. Pain may also become a significant problem with angiomyolipomas.
Renal angiomyolipomas—made up of vascular tissue (angio), smooth muscle (myo), and fat (lipoma)—are benign hamartomas. These hamartomas are well circumscribed groups of cells that multiply excessively, growing as tumors that may or may not cause symptoms. The prevalence of TSC-related renal angiomyolipomas increases with age, and in adults bilateral tumors or multiple tumors in one kidney are common. Angiomyolipomas begin in childhood in many individuals with TSC, but they usually grow very slowly and may not be problematic until young adulthood. Individuals with TSC should have their kidneys imaged at the time of diagnosis and then regularly throughout their lives.
TSC renal cysts are commonly multiple and bilateral. They are the second most frequently occurring kidney manifestation of TSC. Single or multiple renal cysts occur less often in individuals with TSC than do angiomyolipomas, but they may appear earlier. Some cysts may collapse and disappear.
TSC renal cysts are commonly multiple and bilateral. They are the second most frequently occurring kidney manifestation of TSC. Single or multiple renal cysts occur less often in individuals with TSC than do angiomyolipomas, but they may appear earlier. Some cysts may collapse and disappear.
One important research finding was the discovery of the TSC2 gene in close proximity to the gene for polycystic kidney disease (PKD1) on chromosome 16. A small group of individuals with TS have a large segment of chromosome 16 deleted which means that both the TSC2 and PKD1 genes are also removed. These individuals most often will have polycystic kidneys from birth and will require close monitoring and treatment throughout the childhood years.
Individuals with TSC and renal angiomyolipomas have a greater risk of developing malignant kidney tumors than do individuals with renal angiomyolipomas who do not have TSC. As a result, patients with TSC must have their kidney images carefully reviewed by a physician who is knowledgeable about TSC and who can differentiate between angiomyolipomas and other types of kidney tumors. The physician should work closely with a radiologist who can differentiate between malignant and benign angiomyolipomas. Malignant angiomyolipomas should be removed as soon as possible after their detection.