acute angle
| 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) |
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| 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) |
| lichen haemorrhagicus | A papular eruption due to haemorrhage into the hair follicles. (05 Mar 2000) |
| lichen infantum | An eruption of papules and vesicles at the orifices of sweat glands, accompanied by redness and inflammatory reaction of the skin. Synonym: heat rash, lichen infantum, lichen strophulosus, prickly heat, strophulus, summer rash, tropical lichen, lichen tropicus, wildfire rash. (05 Mar 2000) |
| lichen iris | Ringworm with concentric rings of erythematous papules. (05 Mar 2000) |
| lichen lichens on bark | A mutualistic association of a fungus andphotosynthetic organism, either a unicellular alga or a cyanobacterium. Some lichens are used to make natural fabric dyes. (09 Oct 1997) |
| lichen myxoedematosus | A lichenoid eruption of papules or plaques of mucinous oedema due to deposit of glycosaminoglycans in the skin and fibroblast proliferation, in the absence of endocrine disease. See: scleromyxoedema. Synonym: papular mucinosis. (05 Mar 2000) |
| lichen nitidus | A chronic inflammatory disease characterised by shiny, flat-topped, usually flesh-coloured micropapules no larger than the head of a pin. Lesions are localised in the early stages, found chiefly on the lower abdomen, penis, and inner surface of the thighs. Distribution may become generalised as the disease progresses. (12 Dec 1998) |
| lichen nuchae | Lichen simplex of the neck, usually in women. (05 Mar 2000) |
| lichen obtusus | A form in which the papules are large and rounded instead of flattened. (05 Mar 2000) |
| lichen planopilaris | Follicular hyperkeratosis of the scalp with lymphocytic perifolliculitis and lichen planus elsewhere. Synonym: Graham Little syndrome, lichen planus et acuminatus atrophicans. (05 Mar 2000) |