ARTICLE |
wiak, MD, PhDa
ska-Pakie
a, MD, PhDa
gorzata Tomyn-Drabik, MD, PhDb
a Departments of Neurology and Epileptology
b Cardiology, Children's Memorial Health Institute, Warsaw, Poland
c Genetics Laboratory, Hematology Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| ABSTRACT |
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PATIENTS AND METHODS. Patients (154) with tuberous sclerosis complex were evaluated, including clinical assessment, electrocardiography, and echocardiography. Mutations in TSC1 or TSC2 genes were identified in 127 patients.
RESULTS. Cardiac rhabdomyomas were found in 74 (48%) patients. Tumors were most frequent in children younger than 2 years (65%). Tumor regression or disappearance was observed in 37 (68%) of 55 children. However, in 6 (3.9%) of them (aged 10-15 years), cardiac rhabdomyomas were noted to either grow (3 cases) or appear de novo (3 cases), such that the frequency of cardiac rhabdomyomas in adolescents was 6 (54%) of 11. Most (61%) tumors were clinically silent. Clinical manifestations included heart failure (5.4%), arrhythmias (23%), and murmurs (14.9%). One child died as a result of cardiac insufficiency. Cardiac rhabdomyomas were more frequent in theTSC2 (54%) than TSC1 (20%) groups.
CONCLUSIONS. Cardiac rhabdomyomas are seen in the majority of young children with tuberous sclerosis complex. Most produce no clinical consequences and will spontaneously regress. However, during puberty, cardiac rhabdomyomas may enlarge or appear de novo; thus, attention should be paid to potential clinical signs and monitoring by echocardiography should be performed. Cardiac rhabdomyomas were observed more often in the TSC2 group.
Key Words: tuberous sclerosis cardiac tumor echocardiography TSC1 TSC2
Abbreviations: TSCtuberous sclerosis complex CRcardiac rhabdomyoma RVright ventricle LVleft ventricle TSC1tuberous sclerosis complex type 1 TSC2tuberous sclerosis complex type 2
Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the development of distinctive benign tumors in multiple organ systems, including skin, brain, heart, lungs, kidney, and liver. It affects
1 in 6000 individuals but is considered to be as frequent as 1 in 6800 in children.1 Cardiac involvement is relatively common in patients with TSC, usually in the form of cardiac rhabdomyomas (CRs). Although often clinically silent, these lesions can cause arrhythmias and cardiac failure2 and, in one series, have been the most frequent cause of death among <10-year-old children with TSC.3
With the advent of echocardiography, cardiac tumors have been diagnosed more frequently. The incidence of primary cardiac tumors among children presenting to pediatric cardiac referral centers is 0.20%4 and is 0.27% among pediatric autopsies.5 Rhabdomyoma is the most common primary cardiac tumor in infancy and childhood, representing 36% to 42% of tumors in autopsy57 and 79% in clinical series.4
It is currently thought that the majority of children with CRs have TSC. In a review of all cases of CRs published up until 1990, Harding and Pagon8 found that at least 172 (51%) of 335 cases were associated with TSC. Data regarding TSC manifestations in an additional 117 cases were insufficient to confirm the diagnosis of TSC, but if one includes these 117 possible TSC cases, 86% of CRs were related to TSC. The highest proportion of TSC among CRs was reported by Bosi et al,9 who documented TSC in 30 (91%) of 33 patients with CRs. Multiple rhabdomyomas especially are regarded as characteristic for TSC. Tworetzky et al10 diagnosed TSC in 7 of 23 children with a single ventricular tumor and 61 of 64 patients with multiple lesions. Conversely, CRs are found in 47% to 67% of all patients with TSC.1113
However, despite the long recognition of a relationship between CRs and tuberous sclerosis, there have been no previous studies that have assessed their incidence and natural history with mutational analysis of the TSC genes in a large number of patients. Such a detailed characterization is our intent for this report.
| MATERIALS AND METHODS |
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All subjects had a clinical evaluation that included physical examination, echocardiography, electrocardiography, and a chest radiograph. Cardiac ultrasound examinations were performed using a Hewlett-Packard (Andover, MA) machine with spectral Doppler facilities. At study entry, the age of the patients with TSC ranged from 0 to 18 years. In 3 patients, cardiac tumors were found on prenatal sonography, and they were included in this study after birth. Follow-up examinations were performed in 55 patients. The control sonography was proposed every second year to all children with TSC unless the patients required quick evaluation. The follow-up period ranged from 0.5 to 18 years, with a median of 3.5 years.
In 127 patients, TSC gene-mutation identification was performed as described.15
For statistical analyses, Fisher's exact (for cells with size
5) and
2 tests were used. The level of significance was set at P < .05.
| RESULTS |
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Serial echocardiographic examinations were performed in 55 cases, including 38 patients in whom the first examination showed
1 CR. Follow-up ranged from 0.5 to 18 years (median: 3.5 years). Of these 38 patients, tumors disappeared in 7 (18%) and decreased in 19 (50%) patients (Fig 1). In 3 (8%) cases tumors were larger at the follow-up examinations, whereas in 9 patients (24%) they did not change in size. Of the 17 patients without CRs on the first echocardiographic examination, tumors appeared in 3 (18%) of the cases (Fig 2).
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Genetic analysis to identify mutations in TSC type 1 (TSC1) or 2 (TSC2) was performed for 127 patients. TSC1 mutations were found in 15 (12%) and TSC2 mutations in 93 (73%) patients, whereas in 19 (15%) patients no mutation could be identified. Cardiac tumors were seen in 50 (53.8%) of 93 patients with TSC2 mutations, in comparison to 3 (20%) of 15 of those with TSC1 mutations (P < .0001) (Table 3). In the group with no mutation identified, CRs were seen in 7 (36.8%) of 19.
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Analysis of the frequency of CRs by age according to genotype is difficult because of the small number of patients in this series with TSC1 mutations. However, similar to observations on the entire set of patients, patients with TSC2 mutation aged 0 to 2 years had the highest frequency of CRs (29 of 36 [80%]), which dropped significantly in the group of 2- to 11-year-olds (15 of 43 [35%]; P < .0001).
Five patients with TSC1 mutation underwent follow-up echocardiography. Tumor regression was observed in 1 patient, complete resolution was observed in another patient, and in 3 other patients without the CRs on first echocardiography, the results of the examination remained the same. In the TSC2 group, follow-up examination was performed for 36 patients. New tumor appearance was noted in 2 children, and in 2 other patients the existing tumors had enlarged. Tumor regression or resolution was observed in 14 and 3 cases in the TSC1 and TSC2 groups, respectively. In 15 patients, the result of echocardiography remained unchanged.
| DISCUSSION |
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We confirmed that these tumors are seen at their highest frequency in very young children (66% in children <2 years of age). In the majority of patients, there is partial (50%) or complete (18%) resolution of CRs during serial follow-up assessment by echocardiography.
In contrast to previous reports, we have demonstrated that cardiac tumors may grow and/or appear de novo in adolescents with TSC. Because of the significance of this observation, we carefully reviewed the echocardiograms of the 6 patients in whom this was seen. All echocardiographic examinations were performed by the same physician under the same conditions and using the same standards. Moreover, in the 3 patients in whom CRs appeared when none had been seen previously, the same echocardiographic device was used for the initial and follow-up examination. On the basis of these findings, it seems reasonable to perform echocardiography on all adolescents with TSC. However, because of variable dynamics of tumor evolution, it is difficult to establish universal timing of follow-up echocardiography in patients with TSC.
The natural history of CRs is intriguing and quite distinct from that of any other manifestation of TSC. However, another TSC lesion, pulmonary lymphangioleiomyomatosis, is seen exclusively in females, implicating estrogen as a critical factor in stimulating the growth of the smooth musclelike cells that comprise lymphangioleiomyomatosis. Similarly, we hypothesize that maternal transplacental estrogen stimulation accounts for the observation that CRs are seen at their highest frequency and severity in the first months of life.12 The proliferating aberrant myocytes that make up rhabdomyomas are distinctive in their massive accumulation of glycogen and show evidence for complete loss of either TSC1 or TSC2 with high expression of phospho-S6.16 This molecular signature of activation of mammalian target of rapamycin (mTOR) is similar to that seen in many other TSC lesions, consistent with the function of the TSC1/TSC2 proteins in regulating the activation of mTOR.17 Extending this reasoning further, we postulate that the growth/appearance of rhabdomyomas in the small fraction of patients with TSC during puberty reflects the effects of pubertal hormonal changes.
CRs have important diagnostic implications. When discovered prenatally or at birth, CRs are rarely associated with other manifestations of TSC.18,19 In infants, the skin lesions of TSC may not be found even with a Wood light examination, and brain imaging studies (computed tomography or MRI) in early infancy have limited resolution and require general anesthesia. Echocardiography is perhaps the most useful single diagnostic test for TSC in this age group.18 The absence of visible cardiac lesions does not exclude the presence of the disease. One should be always aware that because of echocardiographic resolution limitations, very small tumors may be missed. Recently, MRI was proven to provide valuable information about cardiac tumors in fetuses and children.7,20 It should be noted that early detection of cardiac tumors in fetuses allows consideration of further pregnancy management.19,21
Most patients with TSC with CRs do not exhibit any clinical manifestations.12,22 If cardiac symptoms occur, they are largely a consequence of tumor size or location within the heart.
CRs may be detected in any of the cardiac chambers. In the majority of patients with TSC, the tumors are 5 to 15 mm in diameter. They appear with similar incidence or slightly more frequently on the left side of the heart than on the right12,23,24 and more commonly in the ventricles than in the atria.12,23 In a large study of 47 patients with TSC and CRs, Nir et al25 noted tumors in the LV in 32 patients (68%) (in the LV septum in 38% and the LV apex in 38%) and the RV in 31 patients (66%) (in the RV septum in 38% and RV apex in 32%). Eighteen patients (38%) had tumors located in the LV only, whereas 14 patients (30%) had tumors in the RV only, and 15 patients (32%) had tumors in both the LV and RV. Right atrial tumors were present in 3 patients (6%). In this study, CRs localized predominantly in the RV (35.3%), and the right atrium was the least likely area affected.
In patients with TSC, myocardial involvement and replacement of the ventricular muscle by noncontractile tumor tissue may mimic a cardiomyopathy. In our retrospective studies of children with TSC, we had 6 patients in whom the diagnosis of cardiomyopathy was established in the first months of life.12 After subsequent echocardiographic studies the diagnosis was abandoned, probably because of the regression of the tumor. Fortunately, intramural lesions rarely produce clinical signs. The prognosis for this group of patients is better than for patients with intracavitary tumors. In our study, most CRs were asymptomatic.
Congestive heart failure develops in 2% to 4% of children with CRs.12,25 Only 1 of 47 patients reported by Nir et al25 had the symptoms of heart failure. It is interesting to note that a cardiac murmur may be heard in a relatively small proportion of patients. We detected it in 11 (10%) of 108 children with cardiac masses.
The majority of descriptions in the literature of patients with CRs leading to heart failure are related to masses in the left heart. One of our patients with multiple rhabdomyomas located mainly in the LV outflow tract died at the age of 3 months. Five of 6 infants with TSC and symptomatic CRs reported by Webb et al26 died as a result of cardiac failure; all 6 had large LV lesions.
There is a common opinion that the rhythm abnormalities in patients with TSC are caused by intramural rhabdomyomas interrupting the conduction pathways and leading to ectopic electrical foci or an accessory electrical circuit producing preexcitation (Wolff-Parkinson-White syndrome). Nir et al25 documented Wolff-Parkinson-White syndrome in at least 2 (9%) of 23 patients with rhabdomyomas who had electrocardiograms. In our patients, the frequency of Wolff-Parkinson-White syndrome was not as high (0.65%) but still higher than in the general population (0.15%).
This is also the first report on the phenotype-genotype correlations in cardiac tumors in TSC. We found that CRs are significantly more frequent among patients carrying TSC2 mutation than those carrying TSC1 mutation. Moreover, in patients with TSC2 mutation, the cardiac tumors produced more severe symptoms. Heart insufficiency was seen in patients with TSC2 mutation only, and 1 of them resulted in a patient's death.
| CONCLUSIONS |
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| FOOTNOTES |
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Address correspondence to Sergiusz Jó
wiak, MD, PhD, Department of Neurology and Epileptology, Children's Memorial Health Institute, Aleja Dzieci Polskich 20, 04-730 Warsaw, Poland. E-mail: sergiusz.jozwiak{at}gazeta.pl or s.jozwiak{at}czd.pl
The authors have indicated they have no financial relationships relevant to this article to disclose.
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