• Antiphospholipid antibodies;
  • IgM;
  • memory B cell;
  • recurrent pregnancy losses;
  • rheumatoid arthritis


Recurrent pregnancy losses (RPL) and unexplained infertility (UI) are often associated with the presence of antiphospholipid antibodies (APA). We report one case with RPL, UI, and persistent IgM APA without B-cell isotype switch.

Method of study

(i) A case report of a woman with RPL and UI who eventually developed rheumatoid arthritis and B-cell phenotype study of the case and controls by flow cytometric analysis; (ii) a retrospective cohort study of 1067 subjects with APA test.


A 44-year-old woman with a history of RPL and UI was revealed to have high levels of APA, primarily of IgM isotype: IgM autoantibodies were specific to cardiolipin, phosphatidylglycerol, phosphatidylserine, and phosphatidylinositol. The monitoring of the patient's serological characteristics for 28 months did not reveal the development of IgG APA. B-cell phenotype analysis revealed decreased switched and double negative memory B cells and increased non-switched memory B cells in comparison with normal controls and reported ranges.

A retrospective analysis of APA test revealed that total five patients (5/1067, 0.47%) with similar persistent IgM-only pattern were detected.


Persistent IgM APA without isotype switch may be a rare variant form of APA manifestation, which is associated with dysregulated B-cell subsets.