Background
Small fiber neuropathy (SFN) can be associated with autoantibodies, including those of IgM class with specificity for the trisulfated heparan disaccharide (TS‐HDS) antigen. We hypothesized that, as an IgM autoantibody‐mediated disorder, TS‐HDS‐associated SFN symptoms may be reduced with therapeutic plasma exchange (TPE).
Study methods
This was an observational analysis of all patients referred for TPE from 2018 to 2020 following laboratory confirmation of SFN with TS‐HDS autoantibodies; a loading course of 3 to 5 procedures over 2 weeks was completed, with some patients returning for monthly procedures. The following data were collected: demographics, symptoms and duration, TS‐HDS levels, skin biopsy results, reported responses to TPE, and TPE‐associated adverse events.
Results
Of the 17 subjects, 12 (71%) were female and the mean age was 57.5 years (range 27‐94). The most common reported symptom was lower extremity paresthesia (88% of subjects). The mean number of TPE procedures completed per subject was 9 (range 3‐18), with 71% (12/17) reporting symptomatic improvement or slowed disease progression. About 15% of procedures were associated with an adverse event, with vasovagal reactions being the most common; 53% of patients had at least one adverse event.
Conclusions
Given a reported symptomatic response rate of more than 70%, TPE may be a treatment option for individuals with autoimmune‐mediated SFN associated with increased titers of TS‐HDS IgM autoantibodies. Since TPE‐associated adverse events appear common in this population, close monitoring during procedures is warranted.
Bombay phenotype, an exceptionally rare blood type in individuals outside of Southeast Asia, occurs in approximately 1 in 1,000,000 individuals in Europe. This blood phenotype is characterized by the absence of the H antigen on red blood cells (RBCs) and in secretions. As the H antigen is the structure on which the ABO system is built, individuals lacking this antigen are unable to produce A or B antigens and appear as type O on routine ABO phenotyping. H deficiency does not cause ill effect; however, these individuals produce an anti-H alloantibody capable of causing severe acute hemolytic transfusion reactions when exposed to RBCs that express the H antigen. In this case study, we highlight the incidental discovery of a patient with Bombay phenotype in a North American hospital system, expected test results, the immunologic and genetic basis underlying the Bombay and para-Bombay phenotypes, and methods to ensure availability of compatible blood.
Background: Warm autoimmune hemolytic anemia (WAIHA) is characterized by the development of autoantibodies that react with red blood cells (RBCs) optimally at physiologic temperature, classically resulting in a positive direct antiglobulin test (DAT) for IgG and a panreactive eluate. Babesiosis has been described as a potentiator of WAIHA, and all cases have shown classic blood bank findings. Only rare reports have described autoantibodies, both secondary to babesiosis and overall, with specificity for Kidd antigens.Methods: Antibody detection and identification were performed using IgGspecific column agglutination technology. Jk a antigen phenotyping was assessed using monoclonal reagents and genotypic analysis was performed at an immunohematology reference laboratory. DATs were performed via standard tube methods. The elution was performed using the ELUclear glycine acid red cell elution kit. Results: We report a case of WAIHA induced by Babesia microti infection with an autoantibody with Jk a specificity, originally believed to be a delayed hemolytic transfusion reaction, given the detection of an RBC antibody in close proximity to numerous RBC transfusions. Determination of autoantibody status with anti-Jk a -like reactivity was only confirmed after Kidd antigen genotyping predicted expression of the Jk a antigen.Discussion: Healthcare providers should be cognizant of the potential for babesiosis-induced WAIHA, particularly in individuals who continue to hemolyze despite undetectable parasitemia. Furthermore, this case highlights the possibility for warm autoantibodies to demonstrate Kidd antigen specificity. Though Kidd antigen variants are rare, antigen genotyping may be beneficial, particularly in the context of recent RBC transfusions, which typically preclude accurate serological phenotypic assessment.
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