# Anti-IH in myelodysplastic syndrome

## TL;DR

This paper reports the first case of anti-IH in a Thai patient with myelodysplastic syndrome, highlighting its impact on blood transfusion testing.

## Contribution

First documented case of anti-IH in a Thai patient with MDS, emphasizing its clinical implications for transfusion medicine.

## Key findings

- Anti-IH showed cold-reactivity and weak reactivity at 37°C, complicating antibody identification.
- Transfusion was successful after confirming A1 blood group and anti-IH specificity.
- The case underscores the need for careful testing to avoid transfusion complications.

## Abstract

Anti-IH exhibits complex specificity, strongly reacting with cells expressing both H and I antigens at cold temperatures. Its clinical significance has been increasingly recognized, particularly in patients with hematologic conditions such as myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML).

We present an 83-year-old Thai female with MDS who was transfusion-dependent. She presented with severe anemia requiring an urgent transfusion. The patient was group A RhD-positive. Antibody screening and identification using column agglutination technology (CAT) showed weak polyagglutination. Auto-control and direct antiglobulin tests (DAT) were negative. Red cell typing showed absence of H antigen and presence of A1 antigen. Further testing with cord O cells revealed no agglutination, confirming the A1 blood group with anti-IH. Antibody screening and identification studies showed cold-reactivity, with weak reactivity at 37 °C and in the AHG phase. Crossmatching with two group A leukocyte-poor red cells was compatible, and transfusion was uneventful.

This is the first reported case of anti-IH in a Thai patient. Anti-IH may complicate pre-transfusion testing and mask alloantibodies, necessitating careful interpretation and confirmatory testing to prevent transfusion-related complications.