These observations suggest that deletion of the 5' exons of COL4A6 and of the common promoter of the COL4A5 and COL4A6 genes is not essential for the development of leiomyomatosis in patients with ATS, and that COL4A5_COL4A6 deletions extending into COL4A6 exon 3 may not result in ATS-DL.
No rearrangements were found in COL4A6, with the exception of a deletion encompassing the 5' ends of both COL4A5 and COL4A6 genes in a patient with Alport syndrome and leiomyomatosis.
Alport-leiomyomatosis syndrome is a polygenic syndrome with a dominant X-linked inheritance pattern resulting from a large deletion in the 5' end of the COL4A5 gene coding for the type IV collagen alpha 5 chains.
These results also suggest that leiomyomatosis might be due to the alteration of a second gene involved in smooth muscle cell proliferation, which is located upstream of the COL4A5 gene, and that there might be a contiguous gene deletion syndrome, involving at least the genes coding for congenital cataract, DL and AS.