Precise prenatal diagnosis of tuberous sclerosis by sequencing the TSC2 gene

The Genetics and Diagnosis of Pediatric Neurocutaneous Disorders: Neurofibromatosis and Tuberous Sclerosis Complex

Neurofibromatosis (NF) and tuberous sclerosis complex (TSC) are the two most common neurocutaneous disorders, both transmitted as autosomal dominant or, in the case of NF, also as a mosaic condition. The causative genetic mutations in these neurocutaneous disorders can lead to benign skin changes or uninhibited growth and proliferation in multiple organ systems due to the loss of tumor suppression in mitogen-activated protein kinase and mammalian target of rapamycin signaling pathways. Common clinical features in NF include pigmented lesions, known as café au lait patches, neurofibromas, intertriginous freckles (Crowe's sign), and benign fibrous growths, such as hamartomas in multiple organ systems. Common clinical features in TSC include hypopigmented macules, known as ash leaf spots, in addition to neurologic sequelae, such as autism, seizures, and developmental delays. Advances in genetic sequencing technologies have allowed an exponential expansion in the understanding of NF and TSC. Consensus criteria have been established for both diagnoses that can be confirmed in most cases through gene testing. Once diagnosed, the clinical and diagnostic value of disease-specific surveillance include early identification of benign and malignant tumors. Genetic counseling is important for informed reproductive decision-making for patients and at-risk family members. The improvement in understanding of pathways of pathogenic disease development and oncogenesis in both conditions have produced a new series of therapeutic options that can be used to control seizures and tumor growth. Tremendous advances in life expectancy and quality of life are now a reality due to early introduction of seizure control and novel medications. While we lack cures, early institution of interventions, such as seizure control in tuberous sclerosis, appears to be disease-modifying and holds immense promise to offer patients better lives.

Diagnosis of tuberous sclerosis complex in the fetus

Tuberous sclerosis complex is a dominantly inherited genetic disorder of striking clinical variability. It is caused by mutations in either TSC1 or TSC2 gene, which regulate cell growth and proliferation by inhibition of mTORC1 signaling. TS is characterized by the development of benign tumors in many tissues and organs and its neurological manifestations include epilepsy, autism, cognitive and behavioral dysfunction, and giant cell tumors. With mechanism-based mTOR inhibitors therapy now available for many of its manifestations, early diagnosis of TSC is very important in order to offer appropriate care, long-term surveillance and parental counseling. Fetal ultrasound and MRI imaging techniques have evolved and may capture even earlier the following TSC-associated lesions: cardiac rhabdomyomas, subependymal nodules, cortical tubers and renal cysts. Often these represent an incidental finding during a routine ultrasound. Furthermore, in the past decades prenatal molecular diagnosis of TSC has emerged as an important option for families with a known affected member; however, the existing evidence with regards to the clinical characteristics and long-term outcome of babies diagnosed prenatally with TSC is yet limited and the path that follows early TSC detection merits further research.

Life-threatening tumors of the heart in fetal and postnatal age

OBJECTIVES

To evaluate the role of histology in diagnosis and management of biologically benign heart tumors causing life-threatening symptoms and even death in children and fetuses. The clinical impact of a multidisciplinary approach including 2-D echocardiography, histology, genetics, and cardiac surgery has not yet been fully elucidated.

STUDY DESIGN

Forty-one consecutive antenatal (n = 17) or postnatal (n = 24) detected cardiac masses were evaluated by 2-D echocardiography (in alive patients) or at autopsy, and 12/41 cases with definite histologic diagnosis of primary and benign cardiac tumor were entered in this study.

RESULTS

Rhabdomyomas (n = 6), hemangiomas (n = 3), central fibrous body chondroma (n = 1), fibroma (n = 1), or left atrial myxoma (n = 1) were histologically diagnosed in 4 fetuses and in 8 children. Death occurred in 6 patients showing diffuse or infiltrative tumors, 2/6 experiencing intrauterine death or sudden and unexpected infant death. Seven patients underwent surgery, 4/7 are alive and well at >5 years follow-up, whereas 3 deaths followed partial tumor resection. Two fetuses with extensive tumor/s were aborted. Tuberous sclerosis complex gene mutations were seen in patients with rhabdomyomas.

CONCLUSIONS

Histology represents the best diagnostic approach in life-threatening pediatric cardiac tumors allowing definite diagnosis in cases other than rhabdomyoma and in sudden deaths, influencing clinical management and counselling. 2-D echocardiography remains the main tool for early clinical diagnosis and follow-up. A multidisciplinary approach is advisable because of rarity, difficult management, and possible associations with inheritable diseases.

Considerations for prenatal counselling of patients with cardiac rhabdomyomas based on their cardiac and neurologic outcomes

Cardiac rhabdomyomas are benign cardiac tumours with few cardiac complications, but with a known association to tuberous sclerosis that affects the neurologic outcome of the patients. We have analysed the long-term cardiac and neurological outcomes of patients with cardiac rhabdomyomas in order to allow comprehensive prenatal counselling, basing our findings on the records of all patients seen prenatally and postnatally with an echocardiographic diagnosis of cardiac rhabdomyoma encountered from August, 1982, to September, 2007. We analysed factors such as the number and the location of the tumours to establish their association with a diagnosis of tuberous sclerosis, predicting the cardiac and neurologic outcomes for the patients.Cardiac complications include arrhythmias, obstruction of the ventricular outflow tracts, and secondary cardiogenic shock. Arrhythmias were encountered most often during the neonatal period, with supraventricular tachycardia being the commonest rhythm disturbance identified. No specific dimension or location of the cardiac rhabdomyomas predicted the disturbances of rhythm.The importance of the diagnosis of tuberous sclerosis is exemplified by the neurodevelopmental complications, with four-fifths of the patients showing epilepsy, and two-thirds having delayed development. The presence of multiple cardiac tumours suggested a higher risk of being affected by tuberous sclerosis. The tumours generally regress after birth, and cardiac-related problems are rare after the perinatal period. Tuberous sclerosis and the associated neurodevelopmental complications dominate the clinical picture, and should form an important aspect of the prenatal counselling of parents.

Prenatal molecular diagnosis of tuberous sclerosis complex

OBJECTIVE

The objective of the study was to report experience with prenatal molecular diagnosis of tuberous sclerosis complex (TSC).

STUDY DESIGN

Sequential deoxyribonucleic acid (DNA) studies were performed on amniotic fluid cells and chorionic villi from 50 pregnant women at risk for having a child with TSC. Mutations were determined by gene sequencing and deletion/duplication analysis of the 2 TSC genes.

RESULTS

DNA analysis was successful in 48 of 50 tested fetuses. Mutations were precisely identified in a family member (24) (TSC1 [5]; TSC2 [19]) and/or fetus (11) (TSC1 [3]; TSC2 [8]). Novel mutations were found in 19 individual families, and a probable polymorphism was noted in 4. Second-trimester ultrasound detected 18 fetuses with cardiac rhabdomyomas. There was insufficient DNA in 1, whereas 8 of 17 (47%) had a mutation, 6 (75%) being in TSC2. In 4 of 18 cases, a mutation was detected in the fetus for the first time despite a parent known to have TSC.

CONCLUSION

The value and utility of prenatal diagnosis of TSC by DNA analysis was demonstrated by the results in this series of 50 pregnancies in women at risk of having affected offspring. A family history of TSC or detection of fetal cardiac rhabdomyoma should prompt genetic evaluation and counseling of parents and the option of prenatal diagnosis.

Outcome of antenatally diagnosed cardiac rhabdomyoma: case series and a meta-analysis

OBJECTIVES

Rhabdomyoma, the most common primary fetal cardiac tumor, is often associated with tuberous sclerosis (TS). We aimed to evaluate outcome in cases diagnosed with fetal cardiac rhabdomyoma.

METHODS

This study presents 11 cases with fetal cardiac rhabdomyoma. In addition, all relevant published cases of antenatally diagnosed cardiac rhabdomyoma since 1982 were identified from MEDLINE. We evaluated the following risk factors associated with clinical impact and perinatal outcome: family history of TS, gestational age at diagnosis, tumor size, site and number of tumors, tumor progression, and associated intracardiac and extracardiac anomalies.

RESULTS

In this meta-analysis, 138 cases, including nine newly added by us, were categorized into Group A (107 live babies) and Group B (16 neonatal deaths and 15 intrauterine fetal deaths). Univariate analysis showed that large cardiac tumors (P < 0.0001), fetal dysrhythmia (P < 0.0001) and hydrops (P < 0.0001) were strong predictors of neonatal outcome. Tumor size >or= 20 mm (relative risk (RR), 20.6; 95% CI, 2.2-195.9; P = 0.009) and fetal dysrhythmia (RR, 13.6; 95% CI, 2.9-62.3; P = 0.001) were significantly associated with neonatal morbidity. TS, present in 85/133 (63.9%) cases, was significantly associated with multiple cardiac tumors (P < 0.0001) and family history of TS (P = 0.02).

CONCLUSIONS

Large tumor size and hydrops are significantly associated with poor neonatal outcome, whereas family history of TS and multiple fetal cardiac tumors are associated with TS. Any sonographic detection of a fetal cardiac tumor should warrant further investigation for the possible presence of associated disorders.

Prenatal diagnosis of cerebral lesions in Tuberous sclerosis complex (TSC). Case report and review of the literature

Tuberous sclerosis complex (TSC) is an autosomal-dominant neurocutaneous disorder with multi-organ involvement. The diagnosis is suspected at fetal ultrasound on the discovery of multiple cardiac rhabdomyomas (CRs). They typically develop in utero and undergo spontaneous regression during the first years of live. With developing neuroradiological methods more light is shed on antenatal cerebral lesions like cortical tubers or giant cell astrocytomas. Unfortunately these do not regress, but instead are in principle progressive in size and number, correlated with epilepsy, mental retardation and behavioral problems. It is unknown whether fetal cerebral lesions, are always correlated with a poor neurological outcome or a progressive course of disease. This makes prenatal counseling extremely difficult. We report one case of de novo TSC with first detection of cortical tubers on fetal ultrasound, later developing multiple CRs. The pregnancy was continued and the child is developing well during 16 months of follow-up. Minor motor seizures from the 10th month onwards are successfully treated with Valproate. The published cases with antenatal diagnosis of TSC are revised, trying to get more insight into the postnatal course of prenatally diagnosed TSC. This is crucial, either when termination of pregnancy (TOP) is considered, but even more for proper postnatal care and follow-up.

More than just a bump: the hamartoma syndromes

The hamartoma syndromes detailed in this review are just a few examples of the many genodermatoses now known to be associated with uncontrolled tumor proliferation secondary to mutations in tumor suppressor genes. Knowledge gained through the study of these syndromes has not only improved our understanding of patients afflicted with such conditions, but has also led to significant insight into the important role tumor suppressor genes play in preventing tumor formation and in carcinogenesis. As major strides continue to be made in the identification of causative mutations in the hamartoma syndromes, options for genetic testing will continue to expand. Identification of mutations in PTEN in the various disorders that compose the PTEN hamartoma tumor syndrome illustrates just how such genetic knowledge has altered the way we both categorize and manage certain genetic conditions. As advances continue to be made in this arena, it is quite conceivable that many of the genetic syndromes will be renamed or categorized based on genetic mutations rather than the characteristic clinical features. However, despite these advances, it will still be the astute clinician's recognition of key clinical features that allows the diagnosis of a hamartoma syndrome to be considered.