Thorax
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Pneumonitis is a rare but potentially life threatening side effect of methotrexate treatment for rheumatoid arthritis which needs to be distinguished from interstitial lung disease due to rheumatoid arthritis. ⋯ Methotrexate pneumonitis was associated with lymphocytic alveolitis with a preferential increase in CD4+ cells. This pattern differs from that in interstitial lung disease due to rheumatoid arthritis and may therefore assist in making an early diagnosis of methotrexate pneumonitis.
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Patients with acute leukaemia may have spuriously low arterial oxygen tensions (PaO2). The markedly increased numbers of white blood cells in these patients rapidly consume dissolved plasma oxygen resulting in dramatically decreased PaO2 and calculated oxygen saturations. The case history is reported of a patient with a white blood count of 191 000/mm3 in whom multiple arterial blood gas measurements documented hypoxaemia out of proportion to the clinical picture. Pulse oximetry was used to confirm higher haemoglobin oxygen saturations and to establish the spuriously low plasma oxygen tensions in this patient.