Factor XIIIa in the hamartomas of tuberous sclerosis.

Factor XIII is a blood coagulation factor which may also be produced in an intracellular location. The 'a' subunit of this factor has been found in a number of different cell types and has been shown to stimulate the proliferation of fibroblasts in vitro. We have examined cutaneous, central nervous system and renal lesions from persons with tuberous sclerosis using a standard immunohistochemical assay to see if factor XIIIa is expressed in these hamartomatous growths. We found factor XIIIa in most of the stromal cells composing the skin lesions of tuberous sclerosis as well as in cells of subependymal giant cell astrocytoma of the brain and the stromal cells in renal angiomyolipoma. Expression of factor XIIIa may be of significance in the formation of fibrous growths in tuberous sclerosis.