Long-term safety outcomes of prekillikrein (Fletcher factor) deficiency: A systematic literature review of case reports.
BACKGROUND
Hereditary prekallikrein (Fletcher factor) deficiency is a rare condition characterized by a prolonged activated partial thromboplastin time. Inhibitors of plasma kallikrein have recently been approved for prophylaxis of hereditary angioedema and are under investigation for use in other indications.


OBJECTIVE
We attempted to conservatively assess the impact of long-term inhibition of this pathway by reviewing reportedcomorbidities in patients with hereditary prekallikrein deficiency.


METHODS
We searched several medical literature databases for publications that reported data from patients with hereditaryprekallikrein deficiency (<10% of normal and/or shortening of activated partial thromboplastin time on increased incubationtime). Data reporting of cardiovascular, bleeding, and autoimmune-related diseases were extracted.


RESULTS
Of 1966 publications screened, 45 publications (which represented 53 patients with prekallikrein deficiency) wereincluded. Among 53 identified patients with prekallikrein deficiency, 25 were explicitly defined as asymptomatic, with no comorbidities mentioned in another three cases. Another 16 of the 53 patients were described as having undergone surgery or dental extractions with no complications. Cardiovascular comorbidities were reported in 19 patients, mainly hypertension (9 patients) and cerebrovascular ischemia or stroke (5 patients). Excessive bleeding episodes after surgery were reported in four patients. Autoimmune-related diseases were reported for three patients (two with Graves disease and onewith systemic lupus erythematosus).


CONCLUSION
This review identified patients with hereditary prekallikrein deficiency who reported a spectrum of health outcomes from asymptomatic to infrequent reports of cardiovascular, bleeding, and autoimmune comorbidities. The majority of the reports did not indicate any association between prekallikrein deficiency and comorbidities; however, additional observation is required to confirm the long-term safety of plasma kallikrein inhibition.