Involvement of Virus-Induced Interferon Production in IgG Autoantibody-Mediated Anemia

Infection with viruses, such as the lactate dehydrogenase-elevating virus (LDV), is known to trigger the onset of autoimmune anemia through the enhancement of the phagocytosis of autoantibody-opsonized erythrocytes by activated macrophages. Type I interferon receptor-deficient mice show enhanced anemia, which suggests a protective effect of these cytokines, partly through the control of type II interferon production. The development of anemia requires the expression of Fcγ receptors (FcγR) I, III, and IV. Whereas LDV infection decreases FcγR III expression, it enhances FcγR I and IV expression in wild-type animals. The LDV-associated increase in the expression of FcγR I and IV is largely reduced in type I interferon receptor-deficient mice, through both type II interferon-dependent and -independent mechanisms. Thus, the regulation of the expression of FcγR I and IV, but not III, by interferons may partly explain the exacerbating effect of LDV infection on anemia that results from the enhanced phagocytosis of IgG autoantibody-opsonized erythrocytes.

Increased risk of thrombotic events in cold agglutinin disease: A 10-year retrospective analysis

BACKGROUND

Cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia mediated by IgM autoantibodies that trigger hemolysis via classical complement pathway. Increased incidence of thrombotic events (TEs) has been reported in patients with other forms of hemolysis. The incidence of TEs in patients with CAD is unknown.

OBJECTIVE

Evaluate TE risk in patients with CAD.

PATIENTS/METHODS

This is a matched cohort comparison study evaluating the risk of TEs in patients with CAD and without CAD over a 10-year period. A total of 608 patients with CAD were identified in the Optum Claims-Clinical data set by reviewing clinical notes for CAD terms and matched with up to 10 patients without CAD (N = 5873). TEs were defined as the first medical claim for a TE using International Classification of Diseases, Ninth and Tenth Revision codes. Cox regression models were used to estimate time to first TE. Sensitivity analyses were conducted to estimate TE risk among patients with primary CAD.

RESULTS

At least 1 TE occurred in 29.6% of patients with CAD and 17.6% of patients without CAD. The proportion of patients experiencing venous, arterial, and cerebral TEs were each higher among CAD patients. The overall risk of having TEs was higher in patients with CAD (adjusted hazard ratio [aHR], 1.94; 95% confidence interval [CI], 1.64-2.30). Patients with presumed primary CAD also demonstrated an increased risk of TEs (aHR, 1.80; 95% CI, 1.46-2.22). Patients with CAD with the fewest comorbidities had 2.44-fold higher risk of having a TE (95% CI, 1.70-3.52).

CONCLUSIONS

Patients with CAD have an increased risk of TEs when compared with a matched non-CAD population.

Autoimmune hemolytic anemia in pregnancy: a challenge for maternal and fetal follow-up

Background: Autoimmune hemolytic anemia (AIHA) is a rare entity during pregnancy. The fetal risk is determined primarily by the ability of autoantibodies to cross the placental barrier. Currently, the establishment of a standardized antenatal care in cases with AIHA remains as a pending issue.Cases: Firstly, we describe a case of a 17-week pregnant woman that was diagnosed with cold agglutinin mediated (C3 and IgM) AIHA. Treatment was started with prednisone, showing initial improvement, but requiring intravenous gammaglobulins at 27 weeks. During the fetal follow-up, all studies showed normal results. In the third trimester, when there was a clinic and analytic maternal improvement, an unexpected fetal death occurred. Secondly, we present a case of a 30-week pregnant woman, diagnosed with warm antibody (IgG) AIHA. Despite the ability of IgG to cross the placental barrier, the serial measurements of the Middle Cerebral Artery (MCA) peak systolic velocity were always normal and childbirth occurred at term without any adverse perinatal outcome.Conclusion: During pregnancy, identification of the type antibodies in AIHA is crucial to estimate the potential maternal and fetal risks and to establish the follow-up. The interaction of the complement cascade with the coagulation cascade could be an explanation for a perinatal adverse outcome despite the inability of the IgM to cross the placental barrier.