2. CASE REPORT
A 17-year-old female patient was diagnosed as having heart tumor when she had a routine checkup in a local hospital and transferred to Tam Duc Heart Hospital was admitted to our hospital. The patient was born at full term, normal pregnancy and natural delivery, with no family history of epilepsy. At 5-month-old, the patient started suffering from convulsion after falling down from a hammock. She was then diagnosed with generalized epilepsy and prescribed anticonvulsant medication. From age 2, she experienced partial seizures with eight to ten episodes a year. Throughout the years, she was treated with anti-epileptic drugs including sodium valproate and carbamazepine without successful control of seizures. She stopped studying at age 15 due to intellectual disability.
Physical examination showed facial angiofibromas over her nose, cheeks and forehead, intraoral fibromas and hypopigmented skin lesions (shagreen patch) on different parts of the body (Figure 1). Her biochemical laboratory test was unremarkable. Echocardiography showed chordae of tendinae sclerosis (Figure 2). Chordae tendineae sclerosis and the presence of lipofibroma in midlateral wall of left ventricle were also demonstrated by cardiac MRI (Figure 2). Cerebral MRI revealed multiple 5 to 7 mm nodules in the brain cortex and subependymal zone (Figure 3). Thoracic multi-slide computed tomography (MSCT) showed multiple 3-5 mm nodules in both lungs (Figure 4) . Renal angiomyolipomas of 50x50 mm in bilateral kidneys were revealed by ultrasonography and MSCT (Figure 5). With those characteristic clinical manifestations, we considered that the patient fulfilled diagnostic criteria of TSC.
Next generation sequencing of TSC 1 and TSC2 gene was performed on patient blood sample to confirm the diagnosis of TSC, after obtention of patient’s parents signed informed consent. Library preparation was carried out using Trusight Cancer kit (Illumina, United States) according to the manufacturer’s instructions. Prepared library was sequenced using Illumina Miniseq platform. Variants (SNPs and indels) were called using the Genome Analysis ToolKit (GATK) according to guidelines, and human reference genome hg38.4 Variants with at least 20X coverage were further analyzed using Alamut Visual (Interactive Biosoftware). Synonymous variants, intronic variants outside of the flanking regions, and variants with a minor allelic frequency (MAF) ≥ 5% in the Genome Aggregation (gnomAD) database were excluded based on the American College of Medical Genetics and Genomics (ACMG) recommendations for variant frequency in control populations.5 The patient was found to carry a novel heterozygous frameshift mutation c.2626delA, p.Thr876ProfsTer18 (NM_000548.5) in exon 23 of TSC 2 gene. This mutation was classified as likely pathogenic based on ACMG guidelines. Sanger sequencing was used to confirm the identified mutation (Figure 6). This mutation was not identified in normal subjects according to gnomAD, and was not reported in HGMD, OMIM and Clinvar as associated with TSC.
There is no approved therapy protocol for TSC in Vietnam yet and the follow-up was not possible since the patient lives in distant region from our hospital.