Genitourinary Radiology > Kidneys > Parenchymal > Large Kidney > Tuberous Sclerosis

Tuberous Sclerosis

Tuberous sclerosis is an autosomal recessive disorder caused by mutation of the tumor suppressor genes TSC1 and TSC2. Tuberous sclerosis is a neurocutaneous disorder that affects many organ systems, including the brain, kidneys and skin. Seizures in these patients are usually a result of CNS damage from cerebral hamartomas.

Diagnosis is clinical and requires two major criteria or one major and two minor criteria. The classic triad of seizures, mental retardation, and facial angiofibromas (Vogt’s triad) occurs in less than 50% of patients.

Major criteria include facial angiofibromas, Shagreen patch (connective tissue nevus), three or more hypomelanotic macules, nontraumatic ungula or periungual fibromas, lymphangioleiomyomatosis, renal angiomyolipoma, cardiac rhabdomyoma, multiple retinal nodular hamartomas, cortical tuber, supependymal nodules, subependymal giant cell astrocytoma.

Minor criteria include confetti skin lesions (multiple 1 to 2 mm hypomelanotic macules), gingival fibromas, multiple randomly-distributed pits in dental enamel, hamartomatous rectal polyps, multiple renal cysts, nonrenal hamartomas, bone cysts, retinal achromic patch, cerebral white matter radial migration lines

Radiographically, tuberous sclerosis is suspected when angiomyolipoma is found in patients with simple renal cysts. Angiomyolipomas may hemorrhage at any time, but lesions > 4 cm are often prophylactically resected because their hemorrhage risk is high. When renal lesions don't contain substantial fat in patient's with TS, the presumptive diagnosis is "fat poor" angiomyolipomas. These lesions are indistinguishable from renal cell carcinomas. However, since the lesions are multiple and bilateral and since biopsy is of limited utility, these patient's must be followed closely to exclude growth (resecting multiple bilateral lesions is contraindicated due to complication risks and risks of dimished renal function). If the lesions remain stable, the diagnosis of angiomyolipoma is confirmed, if the lesions grow, they are resected for presumed renal cell carcinoma.

(1) MRI of the brain with gadolinium in a patient with tuberous sclerosis and cerebral hamartomas (arrows).  (2) Contrast enhanced CT scan in the same patient shows bilateral renal masses which are enhancing (M). Some other lesions show demonstrable fat (arrow) in left kidney in additional to bilateral renal cysts (*). There lesions have remained stable over years and are most consistent with "fat poor" angiomyolipomas.

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