T-cell prolymphocytic leukaemia associated with immune checkpoint inhibitor (pembrolizumab).

We describe the case of a man in his 60s with squamous cell carcinoma of the lung with brain metastasis treated with pembrolizumab who subsequently developed T-cell prolymphocytic leukaemia. He was transferred to our hospital with worsening dyspnoea, suspected hyperviscosity syndrome and tumour lysis syndrome. He was intubated and admitted to our critical care unit. Emergent leucapheresis was started due to worsening renal function in the setting of tumour lysis and hyperviscosity syndromes. He continued to deteriorate and required continuous renal replacement therapy. Unfortunately, he eventually died from haemodynamic decompensation. There are only a few anecdotal cases pointing at a possible association between the use of immune checkpoint inhibitors and the progression or exacerbation of secondary haematological malignancies. The poor prognosis of these haematological malignancies warrants further investigation to determine if checkpoint inhibitors increase the risk of developing or propagating these potentially fatal diseases.