February 2024 Quick Question: Rosenthal Syndrome

Forty-two participants answered our February 2024 Quick Question, “What factor deficiency is named Rosenthal syndrome?” Here are the answers:

1. FV: 3 [7%]
2. FVII: 2 [5%]
3. FX: 2 [5%]
4. FXI: 28 [67%]
5. FXII: 5 [11%]
6. FXIII: 2 [5%]

Most of us correctly chose factor XI deficiency, Rosenthal Syndrome. FXI deficiency is an autosomal recessive hemophilia with mild to moderate bleeding. In many cases, hemorrhage occurs only at the time of surgery, childbirth, or trauma. More than 190 mutations result in a prevalence of one in a million unselected individuals. One in 450 Ashkenazi and Iraqi Jews experiences homozygous or compound heterozygous deficiency. The PTT is prolonged, and the PT is normal. The frequency and severity of bleeding episodes do not correlate with FXI levels, and laboratory monitoring of treatment serves little purpose after the diagnosis is established. Hemoleven concentrate is available in Canada and Europe.

Factor X deficiency is rare and was once named Stuart-Prower factor deficiency. Factor XII deficiency is uncommon and was once named Hageman factor deficiency. FXII deficiency is linked to inflammatory cytokines but is not accompanied by bleeding symptoms.

Because FXI deficiency is associated with mild bleeding, researchers have settled on FXIa as a valid target for anticoagulant therapy much as rivaroxaban and apixaban target FX. The principle is that an anti-XIa anticoagulant could generate an antithrombotic effect with minimal risk of hemorrhage, the problem associated with all current anticoagulants. In the abstract of a recent review, Bentounes NK, Melicine S, Martin AC, et al. Development of new anticoagulant in 2023: Prime time for anti-factor XI and XIa inhibitors. J Med Vasc. 2023;48:69-80. doi: 10.1016/j.jdmv.2023.04.002, the authors state, “This review summaries the role of FXI and FXIa in hemostasis, provides evidence of initial success with FXI pathway inhibitors in clinical trials (such as IONIS-FXI_Rx, fesomersen, osocimab, abelacimab, milvexian, asundexian or xisomab 3G3) and highlights the opportunities and challenges for this next generation of anticoagulants. We will watch these developments for efficacy in the next few months.