In a patient with a heterozygous prothrombin gene mutation who has COVID with minimal symptoms, do you recommend prophylactic and/or therapeutic anticoagulation?

If the patient has no history of VTE, I would not recommend any anticoagulant treatment.

Heterozygous prothrombin G20210A polymorphism is a relatively weak risk factor for VTE in comparison to antithrombin, protein C, or protein S deficiency, and in general, is not a finding that should guide decisions about antithrombotic treatment. I'm not aware of any evidence that the presence of the polymorphism in this setting is associated with VTE risk high enough to justify anticoagulation.