A single-center analysis of clinical features of 145 tuberous sclerosis complex—associated renal angiomyolipoma cases in China

Background: Tuberous sclerosis complex (TSC) is a rare autosomal dominant genetic disease with multiple organ system involvement. Renal angiomyolipoma (RAML) is a leading cause of death in TSC-adult patients. The aim of the study was to investigate the clinical features of tuberous sclerosis-associated renal angiomyolipoma among Chinese population so that clinicians can make better clinical diagnosis. Methods: Retrospective review of clinical data of 145 patients with tuberous sclerosis-associated renal angiomyolipoma treated in the Department of Urology, Peking Union Medical College Hospital from January 2014 to January 2019. Analysis of age and gender distribution, tumor stage, and combined clinical manifestations. All analyses used a significance level of 0.05 and were presented in SPSS23.0 software. Results: A total of 145 patients were enrolled. There were 51 males and 94 females. The male to female ratio was 1:1.84, with mean age of 30.50±9.79 years (range 7-58 years). 92 cases were mainly distributed in 21-40 age group, accounting for 63.45%. Among all 6 age groups, 21-30 age group contained the largest number of patients(48 case33.10%). 86 (59.31%) renal angiomyolipoma cases were classified stage 6; 19 cases had a history of tumor rupture and hemorrhage, including 7 selective arterial embolization, 8 partial nephrectomy and 4 nephrectomy. Subependymal nodules (104/122cases, 85.24%), angiofibromas /fibrous cephalic plaque (121 cases, 83.44%), hypomelanotic macules (89 cases, 61.39%), shagreen patch (65 cases, 44.83%) and ungual fibromas (62 cases, 42.07%) were the main combined clinical manifestation. 91.30% ( 42/46) lymphangioleiomyomatosis cases were female . Conclusion: mainly young females Angiomyolipoma.

cephalic plaque, hypomelanotic macules, shagreen patch and ungual fibromas) were common combined clinical manifestations. Lymphangioleiomyomatosis showed an obvious difference in gender distribution Background Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disease [1] . The pathogenesis is the mutation of TSC1 or TSC2 gene, resulting in excessive activation of the mammalian target of rapamycin(mTOR) pathway, which causes disorders of cell growth, proliferation, and angiogenesis. The target organ of TSC includes the nervous system [2] , skin [3] , kidney [4] , heart [5] , lung [6] , liver [7] and almost every organ. As a rare disease with an incidence of 1/5800 [8] , few major cases report the clinical characteristics of TSC at home and abroad. .In order to improve the understanding of this disease, this

Diagnostic criteria
Clinical diagnosis according to criteria of 2012 International Tuberous Sclerosis Complex Consensus Conference [9] Table 1 . 11 major features and 6 minor features were adopted.

RAML Imaging Clinical Classification Standard
The size, number, and kidney morphology of RAML were evaluated by MRI or CT, as shown in Table 2 [10] .

Statistical Analysis
Data were expressed as the mean ± standard deviation (M ± SD) or n (%). All statistical analyses were performed with IBM SPSS Statistics 23. Statistical significance was determined by Chi-square test or unpaired Student's t-test in cases of standardized expression data. P < 0.05 was considered statistically significant.

RAML clinical stage
The clinical stage of TSC-RAML is shown in Table 3. Among the 145 patients, 108 cases, 71.96% were at or above stage 5 with unrecognizable kidneys, of which 86 cases were at stage 6 ( Figure 2). 19 cases had a history of tumor rupture and hemorrhage, including 3 cases in stage 2, 2 cases in stage 4, 2 cases in stage 5 and 12 cases in stage 6, respectively.

TSC-RAML clinical characteristics
Characteristics of 145 TSC-RAML cases were shown in Table 4 . Subependymal nodules was the most common features with a total of 104 in 122 cases (85.24%); facial angiofibromas or fibrous cephalic plaque (121 cases, 83.44%) and hypomelanotic macules 6 (89 cases, 61.39%) were the most common skin lesions; Ungual fibromas, Shagreen patch, and cortical dysplasia were roughly equal in distribution ( Figure 3); only 2 cases suffered from cardiac rhabdomyomas. Among minor criteria the majority manifestation was dental enamel pits (112 cases, 77.24%). In terms of gender distribution, 91.30% (42/46) LAM patients were female, and the proportion was significantly higher than that in other groups, p value 0.05.

Discussion
Tuberous sclerosis complex was first reported by Bourneville in 1880, so it is also known as Bourneville disease, a clinically rare autosomal dominant genetic disease, often involving multiple organ systems [1] . In the 1990s, Fryer [11] and Kandt [12] respectively found two disease-causing genes and named them TSC1 and TSC2. It has been shown that TSC1 or TSC2 mutations can abnormally activate the mammalian target of rapamycin (mTOR) and cause tuberous sclerosis complex [13] .È pidemiology An epidemiological survey in the UK showed a frequency of 1 / 12000 to 1 / 14000 under the age of ten [14] . Osborne et al. claimed a birth incidence was about 1/5800 by improving methods of ascertainment [8] . The age-dependent expression of clinical manifestations was disclosed by Curatolo [15] .

Clinical characteristics
Of cases of TSC-RAML showed that 95.5% (107/112) had at least one of the above-mentioned skin lesions, which is basically consistent with our study results [16] . Subependymal nodules were the most common neurological features (104 out of 122, 85.24%), followed by cortical dysplasias (47 cases, 38.52%). Among 24 patients with a history of epilepsy, subependymal nodules or (and) cortical dysplasias were detected at least. Only 2 cases were diagnosed with cardiac rhabdomyomas, which may be associated with development and outcome of the disease. In a multicenter and prospective studies enrolled 130 infants with definite TSC, cardiac rhabdomyomas was the most common initial feature, accounting for about 59%. Moreover, up to 82% were detected with cardiac rhabdomyomas and prevalence increased with months before 1 year old [5] , then the prevalence decreased significantly after the age of five. Generally, lesions regress spontaneously over time and complete during childhood [15] . In our study, 38.98% (46 in 115 cases) were TSC-LAM patients, of which women accounted for 91.30% (42/46), p value 0.05 (Chi-square test), showing significant differences in gender distribution, which was also the only statistically significant difference among all the major criteria. Lymphangioleiomyomatosis (LAM) is a rare, neoplastic disease that occurs mainly in women [17] . Most patients have clinically progressive dyspnea and repeated pneumothorax. The chest high-resolution CT mainly manifests diffused thin-wall cystic changes in the lungs [9] .There are two types of LAM, sporadic and TSC-LAM, which are caused by mutation in TSC gene. TSC mutation defects tuberin-hamartin protein complex, activates the mTOR pathway and promotes the abnormal proliferation of LAM cells [18] . In women with TSC, the prevalence of LAM ranges from 26% to 38% [6] A single-center, 12-year retrospective clinical study showed that LAM was an age-dependent disease with an increasing risk by about 8%. The prevalence of LAM was about 27% among female TSC patients 21y, and 80% in those 40y [19] This phenomenon may be related to the expression of estrogen and progesterone receptors in and AKT pathway [20,21] As an international disease registry aimed to address knowledge of TSC, TOSCA (Tuberous sclerosis registry to increase disease Awareness) enrolled 2,093 patients with TSC, involving 171 research centers in 31 countries, 1009 males, 1084 females, male to female ratio 1 : 1.07, age distribution 0-70 years, average age 13 years [22] . According to the renal manifestation in TOSCA, 47.2% (987 cases) were diagnosed renal angiomyolipomas with male to female ratio 1:1.35, of which 34.8% had lesions > 3 cm and 22.8% was reported multiple renal cysts. The proportion (89.66% , 130 cases) of TSC-RAML in our study ranged stage 3 or above was significantly higher, while only 17 11.72% multiple renal cysts cases. In addition, the proportion of epilepsy and cardiac rhabdomyoma in TOSCA was obviously higher than those in our study (83.5% vs 16.56%; 34.3% vs 8.00%).
Noticeably, compared with the adults as main subjects of this study (the average age 30.50y, the main age distribution 21-40y, 63.45%), 63.3% TOSCA patients were < 18y, and the proportion of children was as high as 57%, which may account for these differences. And this study mainly analyzed the clinical characteristics of TSC-RAML, which may be another reasons for the difference in statistics.Similar to the results in TOSCA, facial angiofibromas and hypomelanotic macules were the two most common dermatological manifestations. Subependymal nodules were still one of the most common neurological manifestations.

Treatment
Compared with sporadic AML, TSC-RAML is more onset in infancy and more common in female patients. It often presents as a bilateral, multiple, large tumor that grows faster and increases the risk of spontaneous rupture and hemorrhage [23] . Studies have further shown that patients with TSC2 gene mutations have more severe kidney destruction and a higher risk of ruptured bleeding [24] . Renal complications have also become an important cause of death in patients with TSC [25] . Therefore, reasonable and correct treatment is particularly important. Selective arterial embolization and partial nephrectomy as important treatment methods for TSC-RAML have achieved satisfactory clinical results [26] .
A clinical study involving 7 cases of TSC-RAML selective renal artery embolization showed that embolization was safe and effective, and had a small effect on renal function [27] . In addition, partial nephrectomy can maximize the retention of nephrons for complicated RAML [28] .  [16] . During the extension of the trial, the response rate increased to 54% with everolimus median treatment for 28.9 months [29] . A single-center, non-randomized, open-label phase II clinical trial conducted 15 cases of TSC-RAML in China demonstrated that everolimus was well tolerated and effective in Chinese patients with TSC-RAML [30] .

Limitation
Our study was a retrospective observational study of TSC-RAML based on a single center statistics. We provided the largest cases in China, however, some patients were unable to complete all TSC diagnostic criteria examinations due to economic factors or regional medical conditions. In addition, no follow-up data were available in this study because patients were lost to follow-up or the follow-up period was short. Therefore, the above content needs to be improved in the future. Furthermore, subjects of this study were mainly adults with fewer children. Children cases should be collected as much as possible to obtain more complete clinical characteristics of TSC patients in future studies.

Conclusion
This study retrospectively analyzed the clinical manifestations of 145 cases of TSC-RAML.
As the first and largest sample report of TSC in China, it is served as reference for summarizing the characteristics of TSC-RAML in China.

Ethics approval and consent to participate
Not applicable.

Consent for publication
Not applicable as no private information was disclosed.

Availability of data and materials
Data generated in this study are not publicly available. Only summary have been provided in the manuscript.

Competing interests
The authors declared that they had no competing interests.

Funding
The research was supported by the National Natural Science Foundation of China YSZ designed the study. XW and WDW acquired the data. XW, YZ and ZW analyzed the data. XW prepared the first draft. YSZ, YZ and ZW reviewed critically and contributed to the final revision. All authors read and approved the final manuscript.