Lichen

Japanese: 苔癬 - たいせん（英語表記）lichen

It refers to a condition in which papules and nodules of almost the same characteristics and size persist in the same area for a considerable period of time and do not change into other skin eruptions. Representative diseases include the following. (1) Lichen pilaris A disease in which keratotic papules occur in multiple areas of the limbs, especially the extensor side of the upper arms and the lower back and buttocks, in line with the pores. Symptoms appear around puberty and often heal spontaneously later. (2) Lichen amyloidosis A disease in which papules and nodules occur contralaterally on the anterior surface of the lower legs. Each lesion is caused by the deposition of amyloid in the dermal tissue just below the epidermis. It is accompanied by intense itching. (3) Lichen rubra planus A disease in which papules with a central umbilicus appear on the skin, oral mucosa, lips, glans, etc. On the skin, they are often arranged in a band-like or linear pattern. Subjective symptoms are absent or slight, but in rare cases, intense itching occurs. Lesions similar to lichen rubra planus can also occur with the ingestion of drugs or photographic developing solutions.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

ほぼ同じ性状，大きさの丘疹，小結節がある部位に相当長期間にわたって存続し，他の皮疹に変らないものをいう。代表的な疾患に以下のものがある。 (1) 毛孔性苔癬　四肢，特に上腕伸側，腰殿部などに毛孔に一致して角化性丘疹が多発する疾患。思春期頃から症状が表われ，のちに自然治癒することが多い。 (2) アミロイド苔癬　下腿前面に対側性に丘疹，小結節が生じる疾患。個々の病変は表皮直下の真皮組織におけるアミロイドの沈着による。激しいかゆみを伴う。 (3) 扁平紅色苔癬　皮膚，口腔粘膜，口唇，亀頭などに中心臍窩をもった丘疹ができる疾患。皮膚では帯状，線状に配列することが多い。自覚症状はないか，軽微であるが，まれに激しいかゆみがある。また，扁平紅色苔癬に類似の病変が，薬剤摂取や写真現像液で生じる。

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