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Tuberous Sclerosis

Skin lesions and kidney masses • Xray of the Week

What is the diagnosis?

Figure 1. What are the important findings seen on these CT images?

 

Figure 2.

Figure 2A: Axial CT image of abdomen with angiomyolipomas (orange arrows).

Figure 2B: Axial CT image with sclerotic bone lesions (green arrows).

Figure 2C: Coronal CT image of abdomen with angiomyolipomas (orange arrow) and renal cysts (yellow arrows).

Figure 2D: Axial CT of brain with subependymal tubers (red arrows).

 

Discussion:

Tuberous sclerosis complex (TSC) is a multisystem autosomal dominant neurocutaneous syndrome that may present at any age (1). It is due to mutation in the genes TSC1 or TSC2. Diagnosis of TSC can be achieved with genetic analysis, however, it may not identify a mutation in up to 25% of patients (6). This leads to the use of clinical diagnostic criteria, which is separated into major and minor features. Definitive diagnosis is defined as the presence of at least two more major features, or one major and two minor features (6). TSC may affect any human organ with well demarcated benign and noninvasive lesions (2). Organs often involved include the skin, brain, retina, heart, kidneys, and lungs (2). TSC is often associated with neurologic disorders, including epilepsy, mental retardation, and autism (3). However, TSC has a wide clinical spectrum and many patients may have minimal symptoms with no neurologic disability (3).

 

Some characteristic findings that are appreciable on imaging include angiomyolipomas, cysts, sclerotic bone lesions, and subependymal tubers. Renal angiomyolipomas occur in about 75 to 80% of patients over the age of 10 years (4). A majority of these lesions are benign and typically are bilateral and numerous per kidney. Renal cysts are also common findings of TSC and the combination of renal cysts and angiomyolipomas is characteristic of TSC (4). Figures 2A and 2C demonstrate renal angiomyolipomas depicted with the orange arrows on CT. Figure 2C also shows renal cysts indicated by the yellow arrows pointing to the hypodense areas within the kidneys. Another finding is sclerotic bone lesions, which can appear as collection of dense, compact bone within the medullary cavity of bone (5). Figure 2B isolates two areas of sclerotic bone lesions indicated by the green arrows. In addition, subependymal tubers are found in TSC. Subependymal tubers are calcified nodules that are adjacent to the ventricular wall and tend to extend into the ventricular lumen (4). These nodules are commonly observed in the anterior aspects of the lateral ventricles (4). In figure 2D, we can appreciate the subependymal tubers indicated by the red arrows.

 

Currently, there is no cure for TSC, however, the International Tuberous Sclerosis Complex Consensus Group proposes the following recommendations for clinical management. For asymptomatic growing renal angiomyolipomas measuring greater than 3 cm in diameter, first-line treatment consists of mTOR inhibitors (7). Furthermore, a patient’s blood pressure should be evaluated because those with hypertension should be started on a renin-aldosterone-angiotensin system inhibitor, while avoiding angiotensin converting enzyme inhibitor in those treated with mTOR inhibitors (7). Renal angiomyolipomas have abnormal blood vessels that are prone to aneurysm formation and rupture (8). Hemorrhage from angiomyolipomas can be life-threatening, so treatment is advised in symptomatic patients and those with lesions > 4 cm (8). Treatment of renal angiomyolipomas includes the use of selective or super-selective transcatheter arterial embolization which has technical and clinical success rates of 100% and 91% (8,9). Brain surveillance by MRI is recommended every 1-3 years in individuals with TSC under 25 years of age and should be continued for life if the patient develops a subependymal giant astrocytoma to assess its progression (7). Patients with TSC are also at risk for lymphangioleiomyomatosis and should have a baseline high-resolution chest CT with assessment for symptoms of exertional dyspnea and shortness of breath (7). If no lung cysts are appreciated on CT, then repeat imaging is done every 5-10 years. If a cyst is detected, then imaging is done every 2-3 years along with annual pulmonary function testing and 6-minute walk test. Asymptomatic patients with cardiac rhabdomyomas require follow-up echocardiogram every 1-3 years along with 12-lead ECG every 3-5 years to monitor for conduction defects. Thus, radiology plays an essential role as part of the multidisciplinary team in the surveillance and management of tuberous sclerosis complex. 

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References:

  1. Randle, Stephanie Carapetian. "Tuberous sclerosis complex: a review." Pediatric annals 46.4 (2017): e166-e171. doi:10.3928/19382359-20170320-01

  2. Curatolo, P., and B. L. Maria. "Tuberous sclerosis." Handbook of clinical neurology. Vol. 111. Elsevier, 2013. 323-331. doi:10.1016/B978-0-444-52891-9.00038-5

  3. Crino, Peter B., Katherine L. Nathanson, and Elizabeth Petri Henske. "The tuberous sclerosis complex." New England Journal of Medicine 355.13 (2006): 1345-1356. doi: 10.1056/NEJMra055323

  4. Roach, E. Steve, and Steven P. Sparagana. "Diagnosis of tuberous sclerosis complex." Journal of child neurology 19.9 (2004): 643-649. doi: 10.1177/08830738040190090301

  5. Avila, Nilo A., et al. "CT of sclerotic bone lesions: imaging features differentiating tuberous sclerosis complex with lymphangioleiomyomatosis from sporadic lymphangioleiomymatosis." Radiology 254.3 (2010): 851-857. doi:10.1148/radiol.09090227

  6. Von Ranke, Felipe Mussi et al. “Imaging of tuberous sclerosis complex: a pictorial review.” Radiologia brasileira vol. 50,1 (2017): 48-54. doi:10.1590/0100-3984.2016.0020

  7. Krueger, Darcy A., et al. "Tuberous sclerosis complex surveillance and management: recommendations of the 2012 International Tuberous Sclerosis Complex Consensus Conference." Pediatric neurology 49.4 (2013): 255-265. doi:10.1016/j.pediatrneurol.2013.08.002 

  8. Wang, Chengen et al. “Transarterial embolization for renal angiomyolipomas: A single centre experience in 79 patients.” The Journal of international medical research vol. 45,2 (2017): 706-713. doi:10.1177/0300060516684251

  9. Hatano, Takashi, and Shin Egawa. "Renal angiomyolipoma with tuberous sclerosis complex: How it differs from sporadic angiomyolipoma in both management and care." Asian Journal of Surgery (2020). doi:10.1016/j.asjsur.2019.12.008

 

Amer Ahmed is a fourth-year medical student at Midwestern University Chicago College of Osteopathic Medicine. There, he has served as the President for the Medical Business Association and Secretary for the Radiology Interest Group. Before medical school, Amer earned a degree in Economics at Loyola University Chicago and spent some time as an Investment Specialist at Merrill Edge before deciding to pursue his interest in medicine. Radiology intrigued Amer following a back injury requiring him to get an MRI. That is when he was able to appreciate the eye for detail Radiologists possess. Amer is passionate about finance, medicine, and technology.

 

Follow Amer Ahmed on Twitter @amer_ahmed401

 

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Kevin M. Rice, MD is the president of Global Radiology CME 

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

 

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