Since hemophilia, superficially at least, seems to depend on some alteration in the coagulability of the blood, it is frequently regarded as an example of the hereditary transmission of a chemical peculiarity. The exact cause of this peculiar tendency to prolonged bleeding from insignificant or perhaps imperceptible wounds has been sought vigorously by both histologic and chemical means, but as yet without avail. Various observers have described abnormal thinness, or increased cellularity, or fatty degeneration of the vessel walls, but the findings have been far too inconstant to afford a satisfactory anatomic explanation of all the features of hemophilia. Likewise, increased blood pressure can be ruled out, for, although the left heart is frequently enlarged, usually no increased pressure is demonstrable; furthermore, conditions of high blood pressure, such as nephritis, do not cause hemophilia. The theory of "hydremic plethora" is also without good foundation.
The most natural place to look
THE ETIOLOGY OF HEMOPHILIA.. JAMA. 1906;XLVI(8):587-588. doi:10.1001/jama.1906.02510350037006