= Solution
\b[“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.<Overview of Leukemia by Merck Manual Professional Edition>[Introduction; Classification; Findings at Diagnosis table; Leukemoid reaction]{ref}
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.<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]{ref}
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. \b[The dominant clinical problem can be failure of normal blood formation despite an apparent abundance of white cells.]
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