| actinic keratitis | A reaction of the cornea to ultraviolet light. (05 Mar 2000) |
|---|---|
| actinic keratosis | <dermatology> A skin lesion that is abnormally sensitive to the effects of ultraviolet light (sunlight). Thought to be a precancerous skin lesion that is more common in the fair-skinned or elderly individual. Approximately 20% of these skin lesions will develop into squamous cell carcinoma. Prevention includes the use of sun screen agents and the avoidance of drugs (for example tetracyclines) known to cause photosensitivity reactions. Usually a discreet slightly raised, red or pink lesion located on a sun exposed surface. Texture may appear as rough, gritty or scaly. Growths may be biopsied to look for cancer or removed via cryotherapy or electrical cautery. Some topical agents may be used to promote peeling. (27 Sep 1997) |
| actinic prurigo | A form recurring each summer, becoming very severe as long as the hot weather continues. Synonym: actinic prurigo, summer prurigo. (05 Mar 2000) |
| actinic ray | A light ray toward and beyond the violet end of the spectrum that acts upon a photographic plate and produces other chemical effects. Synonym: chemical ray. (05 Mar 2000) |
| actinic reticuloid | Chronic pruritic erythema beginning on sun-exposed areas in elderly males, with marked thickening and ridging of exposed skin simulating lymphoma; there is infiltration by atypical CD8-positive T lymphocytes. Occurs after several years. (05 Mar 2000) |
| pes planus | A condition in which the longitudinal arch is broken down, the entire sole touching the ground. Synonym: flatfoot, talipes planus. (05 Mar 2000) |
| talipes planus | A condition in which the longitudinal arch is broken down, the entire sole touching the ground. Synonym: flatfoot, talipes planus. (05 Mar 2000) |
| moss-lichen wetland | <ecology> A wetland dominated by mosses (mainly peat mosses) and lichens with little taller vegetation. (09 Oct 1997) |
| Wilson's lichen | A primary disorder of the skin resulting in violaceous, polygonal, flat skin lesions that often pruritic (itchy). Seen commonly on the wrists, shins, lower back and genitalia. Involvement of the scalp may lead to hair loss. The cause of lichen planus is unknown, but may occur after the use of a drug (thiazide diuretics, phenothiazines, antimalarials). Treatment with topical corticosteroids is common. In most patients, spontaneous regression of the disease will be seen 6 months to 2 years after onset. (27 Sep 1997) |
| lichen | A large group of symbiotic associations between fungi and green and occasionally blue green algae. Several genera of algae and of fungi are involved and the associations are so stable and of such varied but distinct types that the lichens have been classified into genera and species. A variety of incompatibility phenomena are often manifest between individual lichens. Confined to terrestrial habitats and often used as indicators of pollution status of the environment. (18 Nov 1997) |
| lichen acuminatus | A primary disorder of the skin resulting in violaceous, polygonal, flat skin lesions that often pruritic (itchy). Seen commonly on the wrists, shins, lower back and genitalia. Involvement of the scalp may lead to hair loss. The cause of lichen planus is unknown, but may occur after the use of a drug (thiazide diuretics, phenothiazines, antimalarials). Treatment with topical corticosteroids is common. In most patients, spontaneous regression of the disease will be seen 6 months to 2 years after onset. (27 Sep 1997) |
| lichen agrius | Acute papular eczema of severe type. Synonym: Celsus' papules. (05 Mar 2000) |
| lichen albus | Chronic lichenoid dermatitis with depigmentation. (05 Mar 2000) |
| lichen amyloidosis | Localised cutaneous amyloidosis with pruritic brownish-red papules, most commonly on the lower legs, due to amyloid infiltration of the papillary dermis. Synonym: amyloidosis cutis, lichen amyloidosis. Origin: G. Leichen, lichen, a lichen-like eruption + eidos, resemblance (05 Mar 2000) |
| lichen annularis | <dermatology> Benign granulomatous disease of unknown aetiology characterised by a ring of localised or disseminated papules or nodules on the skin and palisading histiocytes surrounding necrobiotic tissue resulting from altered collagen structures. (12 Dec 1998) |