Nail Disorders
Nail disorders are part of skin disorders because nails arise from modified skin cells which form a region called the matrix, the end of which we can see as the pale crescent underneath the nail. The nail itself is made up of keratin and lies on the nail bed. Nails are affected by a number of diseases: fungal infection, most commonly with agents of the family called dermatophyte - which causes, among other things, ringworm - causes yellowing, thickening and separation of the nail from the nail bed; psoriasis causes tiny pits to form on the surface of the nail and can cause thickening and separation of the nail from the nail bed. White spots are the consequence of minor trauma to the nail bed (and nothing to do with calcium metabolism) - paronychia, or whitlows, are infections down in the side wall of the nail, usually due to nail biting. Yellow nail syndrome is a condition where the nails turn yellow in association with the development of fluid in the chest cavity (called a pleural effusion - see the lung section in the chest cavity) while completely white nail beds are due to low levels of circulating protein, a condition called leuconychia, due to liver disease. Nail growth is a continuous process, which can be arrested during periods of severe illness. This suspension of growth means that when the nail starts to regrow it is thinner, so there is a line running across the nail, called a Beau’s line. There are commonly seen in patients undergoing chemotherapy for malignant disease, when each line represents a course of treatment. Lines running along the nail, or ridges, may be the result of trauma, fungal infection or eczema, as well as other rarer conditions such as an underlying malignant melanoma, or a mucous cyst of the nail bed.
Clubbing of the nails is a condition which starts with loss of the angle where the nail begins, and progresses so that the nail is curved both along its length and from side to side - so that it looks like a club. It occurs in association with a number of underlying diseases: lung disease including cancer of the lung, liver disease including cirrhosis, and congenital heart disease where deoxygenated blood enters the circulation, causing cyanosis, where the lips and skin have a blue tinge. It also can occur in patients with inflammatory bowel disease, such as Crohn’s disease (see the small intestines in the digestive tract section).
Koilonychia is a term used to describe a change in the shape of the nail so that it becomes spoon shaped. It is caused by Iron deficiency anaemia, when the nails may also be very brittle.
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