A 55-year-old woman presents to the emergency department complaining of shortness of breath and fatigue. She reports that her exercise tolerance has been gradually decreasing over the preceding two weeks and that, for the last few hours, she has been struggling to breathe and had to phone an ambulance. She was previously well, normally cycling three times a week. She has no significant past medical history.  On examination, tachypnoea and tachycardia are noted, as well as widespread bruising around her body. On palpation of the abdomen, there is moderate hepatosplenomegaly.

Blood tests show the following: Hb 73, WCC 174 (primarily leukocytes), Plt 24. A peripheral blood film demonstrates auer rods.

Which of the following is the most likely diagnosis?

Options:
explanation: Acute lymphoblastic leukaemia is the most common cancer in childhood (peak age of two to five years old). It is caused by the abnormal proliferation of lymphoid progenitor cells. Patients will often show similar symptoms to AML due to anaemia, thrombocytopenia, neutropenia and organ infiltration. However, painless lymphadenopathy, testicular swelling and central nervous system involvement may also be seen. The age of this patient, leukocytosis, and presence of auer rods would all support a diagnosis of AML, rather than ALL.
name: Acute lymphoblastic leukaemia (ALL)
label: b
answer: no
explanation: Chronic lymphocytic leukaemia is most common in male patients above the age of 60. It is caused by the uncontrolled proliferation of mature B lymphocytes. It typically presents asymptomatically. However, it can also cause painless lymphadenopathy, hepatosplenomegaly, or B symptoms (night sweats, weight loss, fever). Signs of bone marrow failure may be present, but are less common. An incidental lymphocytosis is the most common finding, and a blood film will typically show smear/smudge cells.
name: Chronic lymphocytic leukaemia (CLL)
label: c
answer: no
explanation: A pulmonary embolism may present with sudden onset shortness of breath and tachypnoea/tachycardia like that seen in this patient, but this is usually accompanied by chest pain, and signs of  a deep vein thrombosis. A pulmonary embolism would not explain the blood results or other examination findings in this patient. Patients would not have a gradual onset of shortness of breath over the preceding weeks.
name: Pulmonary embolism
label: e
answer: no
explanation: This patient has acute myeloid leukaemia. This is the most common form of leukaemia in adults, and is caused by the uncontrolled proliferation of myeloid precursor cells. AML typically presents with symptoms of bone marrow failure (fatigue - anaemia, bleeding - thrombocytopenia, infections - neutropenia), as well as signs of infiltration (hepatosplenomegaly). This patient has all of the previously mentioned symptoms and the presence of Auer rods on blood film also supports the diagnosis.
name: Acute myeloid leukaemia (AML)
label: a
answer: yes
explanation: Myeloma may present with signs of bone marrow failure. However, patients most commonly present with back pain, and usually have evidence of hypercalcaemia, renal impairment, anaemia and bone lesions (remembered using the mnemonic CRAB). Urinary Bence-Jones protein would also be present.
name: Myeloma
label: d
answer: no

Correct answer: a