A 47-year-old man was admitted to our hospital because of thrombocytopenia and consciousness disturbance. As his laboratory data showed undetectable activity of a disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) and the presence of ADAMTS13 inhibitor, he was diagnosed with acquired thrombotic thrombocytopenic purpura (TTP). Asymptomatic primary Sjögren's syndrome (SS) and primary hypothyroidism were incidentally diagnosed on screening. After initial plasma exchange therapy and pulse corticosteroid therapy, the patient received rituximab therapy for refractory TTP with "inhibitor boosting" and recovered. TTP secondary to primary SS is rare but can trigger refractory TTP. Treatment with rituximab, which is considered "inhibitor boosting," should be considered when re-exacerbation occurs.