Case report of a rare JMH negative patient and detailed characterization with serological and molecular methods

Background

In a patient with known nummulation who awaited elective surgery an antibody with 100% panel reactivity was detected. Initial screening approaches by IAT gelcard technique with or without enzyme or DTT and inhibition with recombinant blood group antigens focused suspicion onto a JMH HTLA-antibody. Further analysis by extended blood group serology and DNA sequencing should identify the antibody specificity and answer the question if the antibody is relevant with respect to transfusion reactions.

Methods

Extended testing by IAT gel technique under different conditions using specialized differentiation panels (BioRad, CH; DRK-BAD, DE) as well as Capture-R Ready-Screen (Immucor, GA, USA), and rBGA JMH, Yt(a) and Kn(a) for neutralization (Innotrain, DE) were used for antibody differentiation. Additionally, three JMH negative test cells were included. Extended genotyping by in-house PCR-SSP and mass spectrometry covering a wide range of blood group alleles should support definition of the patient"s own blood groups. Because of a suspected JMH negative phenotype, DNA-sequencing should identify the molecular basis of the deficiency. Custom primers specific for JMH were used for amplification and sequencing reactions of all 14 exons.

Results

The patient"s plasma showed continuous moderately positive reactions in the IAT gel technique and capture assay. The papain IAT and DTT treatment were negative. The auto control and eluate of the patient"s RBC were negative too, but the DAT showed a moderately positive reaction. Missing serum reactivity with three JMH negative cells identified an anti-JMH. The patient"s JMH antigen was tested negative as well. Neutralization with rBGA did not result in a negative test, but further clinically relevant antibodies were mostly excluded. Sanger sequencing is currently conducted to determine possible mutations in the SEMA7A gene, which consists of 14 exons. First amplification reactions yielded sufficient PCR-products for downstream analysis.

Conclusion

Extended blood group serology and molecular typing identified a rare anti-JMH in a patient before elective surgery. Even although no clinically relevant hemolysis has been described for this antibody, laboratory analysis and crossmatch should be performed timely if urgent blood transfusion should be needed. Additionally, autohaemotherapy should be considered. In such complex cases extended molecular typing can help to identify the patient"s blood groups and the molecular basis of the deficiency.

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