From Michele Drejka, Barnabas Health: Hi George, We recently saw a patient who is a 72 year old man with factor X activity of 8%, with no significant bleeding history. The incubated mixing study of both PT/PTT corrected without prolongation. The physician would like to have a genetic study done. Do you know of a source for factor X genetics testing? Love the Fritsma Factor.Thank you!
Hello, Michele, and thank you for the compliment. I’ve checked all the clinical labs, including Athena, ARUP, Blood Center of Wisconsin, Esoterix, Machaon, and Quest, that offer molecular and special coagulation testing, and found a number of opportunities to sequence VIII, IX, VWF, and even XIII, but not X (10). I suspect you and your physician colleague will likely need to search for an academic site with molecular research capabilities. Here is an Italian group that has a recent publication on a factor X mutation: Baroni M, Pavani G, Pinotti M, et al, Asymmetric processing of mutant factor X Arg386Cys reveals differences between intrinsic and extrinsic pathway activation. Biochim Biophys Acta. 2015;1854(10 Pt A):1351-6. This is the only reference I’ve found that reports factor X mutation data.
Before searching further, however, given that your patient is 72 and has experienced no bleeding, you may want to suggest examining for amyloidosis, the most common cause for acquired factor X deficiency. See Mumford A, O’Donnell J, Gillmore J, et al. Bleeding symptoms and coagulation abnormalities in 337 patients with AL-amyloidosis. Br J Haematol 2000;110;454–60. I hope this helps.
I agree with the other
I agree with the other respondents that acquired factor X deficiency is far more likely than congenital in a first presentation at age 72. Unless the patient is very well off, spending $2000 on a likely negative genetic test is not something I would encourage. A recommended reference: Menegatti M, Peyvandi F. Factor X deficiency. Semin Thromb Hemost. 2009;35:407–15.
If amyloidosis would be ruled
In case amyloidosis is ruled out, non-amyloid-related causes are also possible:
Lee G, et al. Acquired, non-amyloid related factor X deficiency: review of the literature. Haemophilia. 2012;18:655–63. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2516.2012.02773.x/abstract.
At age 72, acquired factor X
At age 72, acquired factor X deficiency is more likely. Apparently you can get a full sequence done for $1990: https://www.preventiongenetics.com/searchTests.php?val=Factor%20X%20Deficiency&sel=test.