A 25 y.o. female resident had a seizure in the call room. She has no history of seizures and complains only of flank pain after her recovery.

What do you notice on her abdominal CT? Could that lead you to a diagnosis?

Our patient had an angiomyolipoma which is strongly associated with tuberous sclerosis. Angiomyolipomas are benign tumors containing blood vessels, muscle and fat and are considered hamartomas. 70-80% of individuals with tuberous sclerosis  develop these benign tumors.

 Tuberous sclerosis was the cause of our patient’s seizure. In the brain several types of hamartomas form;  giant cell astrocytomas, cortical tubers and subependymal nodules. the subependymal nodules have an unusual triagular shape with the apex near the ventricles. An estimated 90% of individuals with the disease develop neuropsychiatric disorders (seizures, autism, anxiety, and depression)

subependymal lesions on MRI

It is an autosomal dominant disorder with characteristic hamartomas in multiple organs. It is  often the result of mutation in the TSC1 and TSC2 genes however 1 in 4 individuals does not have a known mutation. TSC1 and TSC2 are both tumor suppressor genes  that function according to Knudson’s “two hit” hypothesis.  A second mutation must occur  in the second allele before a tumor can develop. This explains why  despite its high penetrance tuberous sclerosis has widely variable expression.  The disease has a variable course with some patients having no findings or  only some of the characteristic clinical findings.

angiofibromas in tuberous sclerosis

Clinically, the most common findings on exam are:

SKIN: shagreen patches, angiofibromas, hypopigmented macules (ash spots)

NEURO: seizures, subependymal brain hamarto mas seen on MRI

RENAL: angiomyolipomas on CT, often presenting as flank pain

Many more regions of the body can be involved

 Our patient was able to finish her residency and was maintained on seizure medication.

Park B.  Renal angiomyolipoma based on new classification: how to differentiate it from renal cell carcinoma. American Journal of Roentegenology. 2019. Vol 212(3). https://doi.org/10.2214/AJR.18.20408.

Ridler K, Suckling J, Higgins N, Bolton P, Bullmore E (September 2004). "Standardized whole brain mapping of tubers and subependymal nodules in tuberous sclerosis complex". Journal of Child Neurology19 (9): 658–65.

Portocarrero L, Quental K, Samorano L, Oliveira Z, Rivitti-Machado M. Tuberous Sclerosis Complex: Review Based on New Diagnostic Criteria. An Bras Dermatol. 2018;93(3):323-31

Curatolo P, ed. (2003). "Diagnostic Criteria". Tuberous Sclerosis Complex: From Basic Science to Clinical Phenotypes. International review of child neurology. London: Mac Keith Press. 

Knudson A (1971). "Mutation and cancer: statistical study of retinoblastoma"Proc Natl Acad Sci USA68 (4): 820–823.