Life-threatening hemorrhage from acquired factor V deficiency with non-inhibitory, hyperclearance-type antibodies successfully treated with rituximab then belimumab.
Nakako Tanaka-Mabuchi, Shunichiro Hanai, Ryosuke Ito et al.
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Case in brief
A 66-year-old woman with Sjögren’s disease and no previous bleeding tendency presented with rapidly worsening low back pain and severe coagulopathy. Imaging showed right iliopsoas bleeding and pulmonary infiltrates compatible with alveolar hemorrhage; factor V activity was undetectable while other coagulation factors were preserved. Mixing studies suggested deficiency, and plasma exchange produced only transient improvement. Despite a negative Bethesda assay, anti-factor V IgG was detected, consistent with non-inhibitory antibodies and possible accelerated clearance. Glucocorticoids and rituximab improved her condition. After factor V activity fell again during steroid tapering, additional rituximab followed by belimumab restored activity; she remained free of further bleeding for three years.
What made this case unusual
The Bethesda assay was negative despite strongly positive anti-factor V IgG, pointing to a non-inhibitory antibody mechanism rather than measurable factor inhibition. Factor V activity later recovered after belimumab was added following rituximab.
Diagnostic / clinical pearl
In acquired factor V deficiency, a negative Bethesda assay does not exclude an antibody-mediated process; anti-factor V testing may identify non-inhibitory antibodies associated with accelerated clearance.
Why it matters
This case describes sustained recovery after belimumab was added to rituximab when factor V activity declined again and other immunosuppressive agents had proved ineffective.