Clinical Characteristics Of 4 Children With Tuberous Sclerosis Caused By TSC2 Gene Mutation

Objective: The clinical manifestations of tuberous sclerosis are complex,even if the mutation sites are same,the clinical manifestations may be completely different.Gene detection can diagnose the disease.Early detection,diagnosis and treatment can improve the prognosis of the disease.We reported 4 cases of tuberous sclerosis caused by mutation of TSC2 gene,one of which is diagnosed as TSC2-PKD1 contiguous gene syndrome.By suarizing the clinical manifestations,gene characteristics and treatment of the patients,we can further improve the understanding of the disease,which is be of great significance for early diagnosis and treatment.Methods: We selected four cases of tuberous sclerosis as the research object,one of which was TSC2-PKD1 contiguous gene syndrome.The medical history was inquired in detail,the physician examination was comprehensively checked,the laboratory examination and imaging results were collected.HTS was used to identify the TSC gene（TSC1,TSC2）in probands（1,2,3,4）to determine the sites of mutations.MLPA was used to identify the deletion of gene.HGMD Pro and Pubmed database were used to clarify whether the pathogenicity of the variantion has been reported.Sanger sequencing was used to verify the first-generation sequencing results of the probands and his parents.Then,proband1 used Cyto One Array Chromosome microarray to detect the whole genomic DNA copy number variation.Results: Proband 1 was a 2-year-old and 3-month-old boy.The main clinical manifestations were infantile spasm,depigmentation spot,polycystic kidney,hypertension and hematuria after infection.The hepatic and renal functions were normal,genetic metabolic disease was excluded.The EEG showed a peak performance loss.Renal ultrasonography revealed several cysts in both kidneys had replaced the renal parenchyma.Brain magnetic resonance imaging（MRI）showed subependymal nodules.Proband1 met two main criteria: 1.subependymal nodules 2.depigmented spots;and a secondary criterion: multiple renal cysts.We identified a deletion within TSC2 by MLPA.The results showed large heterozygous deletions in the TSC2 gene,involving exons 12–42.The mutation has not reported.The mutation in TSC2 gene of his parents and sister was not found,so it was considered as a de novo mutation.Combined with early-onset renal cysts,we detected the partial TSC2 exons 12-42 in addition to the partial PKD1 gene deletion by array-CGH analysis.TSC2-PKD1 contiguous gene syndrome was diagnosed by gene analysis.After the treatment of topiramate,the patient had repeated convulsions.After the addition of rapamycin,the convulsions were relieved,the renal cysts did not increase,and the renal function did not deteriorate.Proband 2 was a 2-year-old and 5-month-old girl.The main clinical manifestations were infantile spasm and depigmentation spot.The hepatic and renal functions were normal,and genetic metabolic disease was excluded.The EEG showed a peak performance loss.Brain MRI showed subependymal nodules.Proband 2 met the two main criteria: 1.depigmented spots 2.subependymal nodule.It was found in TSC2 gene c.4663-2A> G（the penultimate nucleotide in the front intron of coding region 4663 changed from A to G）,which was a heterozygous splicing mutation.The mutation has not been reported.The mutation in TSC2 gene of her parents and brother was not found by Sanger sequencing,so it was considered as a de novo mutation.After treatment with topiramate,sodium valproate,rapamycin,the convulsions were decreased to 2 times per day.The proband 3 was a 2-year-old 6-month-old boy,the clinical manifestations were infantile spasm and depigmentation spots.The hepatic and renal functions were normal,and genetic metabolic disease was excluded.EEG showed a peak performance loss.Brain MRI showed subependymal nodules.The proband 3 met two main criteria :1.depigmented spots 2.subependymal nodules.It was found in TSC2 gene c.4662 + 1G > A（the first nucleotide in intron after coding region 4662 changed from G to A）,The pathogenicity of the mutation had been reported.Because the disease is autosomal dominant inheritance,the mutation in TSC2 gene of his parents was not found by Sanger sequencing.So it was considered as a de novo mutation.After treatment with topiramate and prednisone,the frequency of convulsions was decreased.Proband 4 is a 2-year-old girl.The clinical features are arrhythmia,cardiac rhabdomyoma,epileptic seizure and depigmentation spot.EEG showed that there were a large number of 3-4Hz moderate-high amplitude sharp-slow wave complex waves in the right occipital parietal posterior temporal region,and right occipital region is significant.Brain MRI showed subependymal nodules,cardiac ultrasound showed multiple rhabdomyomas.Proband4 met three main criteria: 1.depigmented spots 2.cardiac rhabdomyoma 3.subependymal nodule.It was found in TSC2 gene c.5246₅259del.This is a frameshift variant,which resulted in the change of amino acid synthesis starting from arginine and terminating at the 21 st amino acid（P.Arg1749hisfster21）.We also discover the heterozygous nucleotide variation of c.5259+1₅259 + 13del（the deletion of the first to the 13 th nucleotide in intron after 5259 nucleotide in coding region）,which is a splicing variation.The mutation has not been reported.The proband’s father was heterozygous,but no mutation was found in his mother.The patients were treated with antiarrhythmic drugs and with rapamycin to control the convulsions.One year later,the convulsions were controlled.No rhabdomyoma was found in echocardiography.Conclusion: 1.The variations of arr16p13.3（2113376-2147267）,c.4663-2A> G and c.5246₅259del are novel mutation.According to the American Society for medical genetics and genomics（ACMG）,the mutation of TSC2 gene is pathogenic.2.The phenotype of TSC is highly variable.The same mutation site of TSC2 gene was found in proband 4 and her father.The proband 4’age of onset was early and her condition was severe,however her father had only depigmentation.3.There is no report of TSC2-PKD1 adjacent gene syndrome in infancy in China.We analyze the clinical characteristics of proband 1 to deepen the understanding of the disease,which can help us identify the disease early.