Pulmonary Langerhans Cell Histiocytosis in pre-existing chronic myelomonocytic leukaemia: a rare association.
Learning points for clinicians

The association of PLCH in a patient with established CMML is rare. Both conditions are associated with disordered cellular proliferation of monocyte progenitor cell derivatives and chromosome 7 aberrations. The association between LCH and CMML will require further study. Cladribine offers a treatment option for single system PLCH in ex-smokers.

A 72-year-old lady with a 58 pack year smoking history presented with a 2 week history of dyspnoea, lethargy, night sweats and abdominal pain. Past medical history was significant for rheumatoid arthritis, chronic myelomonocytic leukaemia (CMML), diabetes mellitus and previous breast cancer. She was not on any immunosuppression or pneumotoxic drugs. Examination revealed oxygen saturations of 96% on air and signs of her previous breast surgery but was otherwise non-contributory. Blood tests were notable for an elevated white cell count of 21 × 109/l (neutrophils 12.5 × 109/l, lymphocytes 4.2 …