Detection of HTLV-I tax-rex and pol gene sequences of thymus gland in a large group of patients with myasthenia gravis.

We report in this study the use of polymerase chain reaction (PCR) for the amplification of the genomic DNA, isolated from thymic tissue, using the primers flanking HTLV-I/II tax-rex genes and the sequence method to analyze the HTLV-I pol sequence of 27 Italian patients with myasthenia gravis. These molecular methods showed that 92.5% of patients tested positive for tax gene and 55% for pol genes; 55.5% samples were positive for both the tax gene of HTLV-I/II, and the pol gene of HTLV-I. Histologic investigation of the thymus showed that 15 samples had thymic hyperplasia, 93% tested positive for the tax gene, and 40% tested positive for both the tax and pol genes of HTLV-I. In contrast, 91.6% of thymoma-positive samples were positive for tax gene I/II and 75% positive for both genes, tax and pol type I. The sequence analysis of PCR product for tax and pol genes confirmed that these amplified products were HTLV-I, with minimal variations. Our date suggested that either HTLV-I or part of the virus genome is involved in the etiopathogenesis of myasthenia gravis.