# Blood side effects of checkpoint inhibitors: low platelets, haemolysis, neutropenia and marrow failure

Source: https://onco.cc/protocols/irae-haematological/  
OnCo record `irae-haematological` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Rarely, immunotherapy makes the immune system attack blood cells, causing low platelets (easy bruising or bleeding), destruction of red cells (tiredness, breathlessness, yellow skin, dark urine) or low white cells (infections). These are found on blood tests and treated with steroids and other medicines, usually with a haematologist involved.

## Summary

Uncommon (under 1% in one series of 745 patients on PD-(L)1 inhibitors) but potentially life-threatening (SITC 2021). The commonest are immune thrombocytopenia (median onset 41 days) and autoimmune haemolytic anaemia (median 50 days, more frequent on PD-(L)1 than CTLA-4 inhibitors). Neutropenia appears at a median of 10.5 weeks; aplastic anaemia is rare, hard to treat and often does not resolve; HLH (median 26 days) is the most dangerous. In a small series, 43% of patients rechallenged after a haematological irAE had a recurrence.

SITC 2021: work up each with a blood count, film and the relevant tests (clotting and LDH for thrombocytopenia; reticulocytes, Coombs test, LDH and ADAMTS13 for haemolysis; ferritin and soluble IL-2 receptor for HLH), separate immune causes from chemotherapy, and treat by haematological standard of care: prednisone 1 mg/kg for ITP (LE: 1) with IVIG for severe ITP (LE: 1) and rituximab as an option (LE: 2); prednisone 1 mg/kg for haemolysis (LE: 3) with IVIG if refractory (LE: 3); prednisone with G-CSF for immune neutropenia (LE: 3); ciclosporin or ATG for aplastic anaemia (LE: 4); steroids with etoposide or tocilizumab for HLH, under haematology (LE: 3). ASCO 2021 (abstract) makes haematological toxicity an exception to continuing treatment at grade 1.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: haematological irAEs; hematologic immune-related adverse events; checkpoint inhibitor immune thrombocytopenia; ICI-related ITP; checkpoint inhibitor haemolytic anaemia; immune-related neutropenia; checkpoint inhibitor aplastic anaemia; ICI-related HLH
- Tags: protocol; irae; haematology

## Connected records

- protocols: [Restarting a checkpoint inhibitor after an immune-related side effect](https://onco.cc/protocols/irae-rechallenge/)
- technologies: [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/)
- drugs: [Atezolizumab](https://onco.cc/drugs/atezolizumab/), [Avelumab](https://onco.cc/drugs/avelumab/), [Cemiplimab](https://onco.cc/drugs/cemiplimab/), [Dostarlimab](https://onco.cc/drugs/dostarlimab/), [Durvalumab](https://onco.cc/drugs/durvalumab/), [Etoposide](https://onco.cc/drugs/etoposide/), [Human normal immunoglobulin (IVIg)](https://onco.cc/drugs/human-normal-immunoglobulin/), [Ipilimumab](https://onco.cc/drugs/ipilimumab/), [Nivolumab](https://onco.cc/drugs/nivolumab/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Prednisone](https://onco.cc/drugs/prednisone/), [Rituximab](https://onco.cc/drugs/rituximab/), [Tocilizumab](https://onco.cc/drugs/tocilizumab/), [Tremelimumab](https://onco.cc/drugs/tremelimumab/)
- institutions: [American Society of Clinical Oncology (ASCO)](https://onco.cc/institutions/asco/), [European Society for Medical Oncology (ESMO)](https://onco.cc/institutions/esmo/), [Society for Immunotherapy of Cancer](https://onco.cc/institutions/sitc/)
- terms: [Immune-related adverse events (irAEs)](https://onco.cc/terms/irae/), [Thrombocytopenia](https://onco.cc/terms/thrombocytopenia/)
- key papers: [ASCO 2021 guideline: how to recognise and manage the immune-related side effects of checkpoint inhibitors](https://onco.cc/key-papers/paper-asco-irae-guideline-jco-2021/)

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