Acknowledging that HCM has been previously reported in rare instances of CML and MPN (Khoury et al., 2012[3]; Toro-Tobón et al., 2017[4]), the rationale for reflexive screening of the BCR-ABL1 and JAK2 V617F rearrangements in patients presenting with hypercalcaemia without other evidence of an MPN is unfounded. Here, JAK2 is linked to myeloproliferative neoplasm.