Mutations in FBN1 cause the autosomal dominant condition, Marfan syndrome. A single‐base mutation that results in a skipping of exon 2 of FBN1 was found in a Marfan patient. By sequencing this proband's entire FBN1 gene and comparing the mutated DNA sequence with proband's unaffected family numbers, we confirmed this alteration was the causative mutation. The skipping of exon 2 creates a frameshift and premature termination codon, and forms a truncated fibrillin‐1 composed only of 55 amino acids of N‐terminus plus 45 nonsense amino acids. The mRNA transcription levels of the mutated FBN1 allele and the deposition of fibrillin‐1 into extracellular matrix in fibroblast cells culture were assessed. © 2001 Wiley‐Liss, Inc.