Purpura, or THE PURPLES, is a malady which is often erroneously placed amongst the diseases of the skin. It is in reality a blood disease, and is characterised by the appearance of small round spots, of a deep purple colour, which are seen first and most abundantly on the legs, and afterwards extend to the arms and trunk. They are accompanied by no local pain, are not effaced by pressure (being due to a drop of blood extravasated beneath the cuticle or in the structure of the skin itself), do not rise above the surrounding surface, and are sometimes intermixed with livid patches resembling bruises; and, before disappearing, both the round spots and the patches undergo the same change of colour which a bruise undergoes. These spots are not peculiar to the skin, but occasionally occur upon internal surfaces and in the tissues of viscera. Passive hæmorrhages from the mucous membranes frequently accompany the external symptoms. There is usually much debility, and often a great tendency to faintness. The duration of the disease varies from a few days to a year or more. Slight cases are devoid of danger, and even the hæmorrhagic cases usually recover, unless the bleeding has been excessive or the blood has been extravasated into a vital organ.
Precisely similar appearances occur in the course of other diseases, especially scurvy, severe anaemia, scarlet fever, and smallpox. But the name purpura should be restricted to the cases in which no such disease is discoverable.
The causes of purpura are obscure. The treatment which succeeds best varies in different cases, but the main indication always is to correct the condition of the blood. Arsenic, turpentine, acetate of lead, gallic acid are the drugs which are generally most beneficial; rest in bed, light diet, and laxatives are desirable at the commencement. When there is reason to believe that the disease is dependent upon depressing influences a nutritious diet, tonics, and stimulants are required; but chalybeates should be avoided. If the hæmorrhage proceeds from accessible parts, local measures, such as the employment of ice or strong astringents, should also be had recourse to.