Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder resulting from pathologic mutation of the fibrillin-1 gene (FBN1) on chromosome 15. The clinical features are not obvious in children, so diagnosis may be delayed if there is no family history. First case, a 6-year-old boy is referred for abnormal electrocardiography (Borderline prolonged QT) beforehand his tonsillectomy. His arm span–to-height ratio was 0.96 and other clinical features of MFS were not yet apparent. On his echocardiogram, the aortic dilatation (z score>2) was noticed and gene evaluation demonstrated missense variant (c.7606G>A) in 62 exon of FBN1 gene. Second case, a 14-year-old healthy boy visited our hospital with dizziness and pre-syncope. We confirmed his high arm span–to-height ratio (1.01) and myopia. On his echocardiogram, the aortic dilatation (z score>2) was showed and he was diagnosed with MFS through the gene evaluation of missense variant (c.4267G > A) in 2 exon of FBN1 gene.
