“Leukhæmia” denotes leukaemia: historically a persistent excess of colourless corpuscles in the blood, now understood as a group of malignant disorders of blood-forming biological cells. It is distinct from a temporary rise of ordinary leukocytes during inflammation or infection.
The historical laboratory finding was an unusually large proportion of colourless blood corpuscles on microscopy, often accompanied by enlargement of the spleen or lymph nodes. Such a blood appearance did not mean that ordinary pus had simply entered the circulation. The present classification separates acute and chronic disorders and myeloid and lymphoid lineages. The abnormal population can interfere with production of normal red blood cells, platelets and effective leukocytes in the bone marrow. A high total white-cell count is common, but some acute leukaemias present with a normal or low count; the count alone is neither a complete definition nor a modern subtype diagnosis.[ref]
Overview of Leukemia by Merck Manual Professional Edition. Introduction; Classification; Findings at Diagnosis table; Leukemoid reaction
The symptoms follow several mechanisms:
- Reduced normal red blood cell production causes anaemia, with pallor, fatigue, weakness, exertional dyspnoea and sometimes palpitations.
- Reduced platelet production can cause easy bruising, pinpoint petechiae, nosebleeds, bleeding gums or other haemorrhage. Bleeding is a tendency rather than an inevitable finding in every subtype.
- Defective production or function of effective leukocytes predisposes to infection, fever, mouth lesions and slow recovery from infections. A large number of abnormal leukocytes does not guarantee normal defence.
- Expansion or infiltration of the bone marrow can produce bone pain. Enlargement of lymph nodes, the spleen and sometimes the liver may produce visible swellings, abdominal discomfort or early fullness after eating.
- Systemic illness can cause diminished appetite, loss of body mass and night sweats. Conversely, some chronic leukaemias are initially detected in apparently well people.
These are possible manifestations, not a required syndrome in every affected person.[ref]
Leukemia by MedlinePlus. What is leukemia?; Symptoms; Diagnosis
[ref]Leukemia by the American Cancer Society. How leukemia starts; Features and symptoms of acute and chronic leukemia
For an 1866 explanation, the important connection is between the persistent abnormal blood picture, enlargement of blood-forming or lymphatic organs, progressive debility and bleeding. Modern diagnosis goes further: a complete blood count with differential and a stained blood film establish which cellular populations are abnormal; selected bone marrow studies, immunophenotyping and genetic tests identify the disease. A microscope image of numerous white corpuscles is the beginning of that distinction, not proof of every later molecular category. The dominant clinical problem can be failure of normal blood formation despite an apparent abundance of white cells.
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