An 18 year old man developed profound neutropenia 14 months post completion of escalated BEACOPP chemotherapy for stage 4 classical Hodgkin’s lymphoma. Restaging confirmed continuing complete remission. A series of three bone marrow biopsies in the 5 months following the onset of neutropenia demonstrated maturation arrest at the band form stage with no evidence of disease relapse. He had no response to treatment with granulocyte colony stimulating factor (GCSF), intravenous immunoglobulin (IVIg), and prednisone. His neutropenia was complicated by recurrent folliculitis requiring repeated treatment with intravenous and oral antibiotics. This patient underwent extensive investigations including a targeted panel for primary immune deficiencies of the innate immune system and those causing immune dysregulation – ELANE, HAX-1 and CSF3R which were negative. Strong neutrophil antibodies to HNA-1a were subsequently detected. He was commenced on intravenous methylprednisolone which had no effect on his neutrophil count. Weekly rituximab for four doses was commenced, which resulted in a normalisation of his neutrophils after the completion of four doses. He was planned to commence sirolimus therapy if the rituximab therapy had not successfully treated his neutropenia, as there is some evidence for its efficacy in the setting of mutations upstream of the mTOR pathway (Rao & Oliveira, 2011). In the event that he relapses, sirolimus therapy would be our next treatment option. This case highlights an unusual cause of late onset immune-mediated neutropenia post chemotherapy and the difficulties involved in diagnosis and treatment.