Keloid - Keloid (English spelling)

Also called crab podocarpus, this condition refers to a condition in which a wound on the skin becomes raised afterwards; histologically, it is seen to be an abnormal proliferation of connective tissue, but the true cause is still unknown. It is often seen after burns, cuts, folliculitis, and BCG injections; the scar begins to rise 1-2 months after the injury and can take on various shapes, including circular, oval, linear, crab leg, and mushroom-like. It is most common on the face, extensor side of the upper arm, scapula, and sternum, and is often accompanied by itching as it grows. There are racial differences, with it being less common in whites and more common in blacks, and also seen quite frequently in Asians.

There are two types of keloids:

(1) Keloid scars: These are scars that are raised only in the area of ​​the wound or injury, and are characterized by not growing larger than the area of ​​the injury. Most of them flatten over time (several years to 10 years), and redness, pain, and itching often disappear within three years.

(2) True keloids: These are related to a predisposition to keloids and occur in the aforementioned areas where they are most likely to occur. The protrusion continues to extend along the course of the skin's elastic fibers, resembling stretched mochi (rice cake), and the center tends to fade and flatten.

For treatment, continuous compression with a sponge is effective if the condition has persisted for less than three months since onset. For conditions present for more than three months, compression therapy is combined with local steroid injections, pressure application with a Dermojet device, and rubbing in of steroid cream. If the keloid is large and highly elevated, the area is excised and a thin split-thickness skin graft of about 0.3 mm is performed. Radiation is only effective in early-stage cases and is ineffective in conditions present for more than a year. Similar treatment is used for true keloids, but they do not respond easily.

[Shigeo Ikeda]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

蟹足腫(かいそくしゅ)ともいい、皮膚に受けた傷があとになって盛り上がってくる状態をさし、組織学的には結合織が異常に増殖した状態がみられるが、真の原因はまだつかめていない。熱傷（やけど）、切り傷、毛包炎、BCG注射後にしばしばみられ、受傷後1～2か月を経てから瘢痕(はんこん)が隆起し始め、円形、楕円(だえん)形、線状形、蟹足（カニの足）形、キノコ状形など種々の形態を呈する。顔面、上腕伸側、肩甲骨部、胸骨部などに好発し、増大時にしばしば瘙痒(そうよう)を伴う。人種的差異がみられ、白人に少なく黒人に多く、黄色人種でもかなり高頻度にみられる。

　ケロイドには次の2型がある。

(1)瘢痕ケロイド　傷または創を受けた範囲に限って瘢痕が隆起する状態で、外傷を受けた範囲より大きくはならないのが特徴である。大部分のものは年数がたつ（数年から10年）と扁平(へんぺい)化し、潮紅、痛み、かゆみなどは3年以内に消失することが多い。

(2)真性ケロイド　ケロイド体質と関係があり、前記の好発部位に生じ、その隆起は皮膚の弾力線維の走行に従って伸び続け、餅(もち)を引き伸ばしたようになり、中心部は退色扁平化する傾向がある。

　治療は、発症後3か月以内ならスポンジによる持続圧迫が有効である。3か月以上のものでは圧迫療法とステロイド剤の局所注射やダーモジェット器による圧入、ステロイドクリームの擦り込みを併用する。ケロイドが大きく隆起が高度の場合には、同部を切除後、0.3ミリメートル程度の薄めの分層植皮を行う。放射線は早期のものにのみ有効で、1年以上経たものでは無効である。真性ケロイドにも同様の治療を行うが、容易に反応しない。

［池田重雄］

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