Unpredictable neutropenia in a BTHS patient. This graph shows a routine neutrophil profile from a BTHS patient who was not receiving G-CSF and had no clinical explanation for changes in neutrophil counts. It demonstrates that some BTHS patients can transition rapidly from severe neutropenia to high normal neutrophil counts. This emphasises the importance of not using presence/absence of neutropenia at presentation of male DCM as a critical determinant of whether testing for BTHS is performed. Furthermore, BTHS patients can present with bacterial infection in the context of a normal neutrophil count, infection having commenced when severely neutropenic just one or two days previously.