蕁麻疹  (風疹,風爛,風癩) urticaria

Case Report

Case History

A 38‑year‑old gentleman presented with a pruritic skin rash persisting for several months. The rash was transient, with individual lesions lasting less than 24 hours, and no identifiable precipitating factors.

On dermatological examination, sharply demarcated wheals were observed. Lesions varied in size from <1 cm to >8 cm, appearing erythematous or skin‑colored with an erythematous rim. Morphology included round, oval, arciform, annular, and serpiginous shapes, reflecting confluence and resolution in some areas with progression in others. The distribution was generalized. Lesions were pruritic and transient, resolving within 24 hours. No triggers were identified.

By definition, the patient was diagnosed with chronic idiopathic urticaria. He responded well to oral cetirizine. He was advised to avoid potential exacerbating factors such as stress, alcohol, and NSAIDs. Chronic idiopathic urticaria typically persists for 1–3 years before spontaneous remission.

Discussion

Acute vs. Chronic Urticaria

Diagnostic criteria for acute urticaria:

1. Pruritus
2. Wheals lasting <24 hours
3. No residual pigmentation
4. No desquamation
5. Condition duration <6 weeks

Approximately 15% of acute urticaria cases progress to chronic urticaria. Systemic symptoms (fever, gastrointestinal upset, arthralgia) are more common in children.

Causes of acute urticaria:

• Allergic (IgE‑mediated mast cell sensitization):
  • Foods (shellfish, crab, chicken)
  • Drugs (penicillin, radiocontrast media)
  • Immunizations
  • Latex
• Non‑allergic:
  • Viral infections (especially in children)
  • Drugs (morphine, aspirin, ibuprofen)
  • Histamine ingestion (spoiled fish)

Investigations:

• Detailed history (food, drug exposure, infections)
• RAST (serum specific IgE) or allergen prick testing
• Review of drug history

Management of acute urticaria:

• Short tapering course of prednisolone
• Non‑sedating antihistamines once daily
• Calamine lotion or menthol‑containing emollients

Chronic Spontaneous Urticaria

Etiology:

1. Idiopathic (>50%) – possible association with H. pylori
2. Immunological (30–50%) – autoimmune urticaria with thyroid autoantibodies or IgG autoantibodies against FcεRI or IgE; confirmed by autologous serum skin test (ASST)
3. Non‑immunological/allergic factors:
   • Morphine (direct mast cell activation)
   • Aspirin/NSAIDs (altered leukotriene pathways)
   • ACE inhibitors (angioedema via kinin pathway)

Exacerbating factors: stress, alcohol, NSAIDs, ACE inhibitors, viral illness, menstruation.

Management:

• Avoid triggers (stress, alcohol, NSAIDs, ACE inhibitors)
• Treat acute flares: tepid showers, menthol creams, oral chlorpheniramine, short course of steroids
• Long‑term: non‑sedating antihistamines, H2 antihistamines
• Resistant cases: montelukast, cyclosporine, combination antihistamines

Other Forms of Urticaria

• Physical urticarias: dermatographism, delayed pressure, cholinergic, cold, solar, heat, aquagenic, vibratory, exercise‑induced.
• Angioedema: may occur independently or with urticaria.

病例報告

病史

一位 38 歲男性因持續數月的皮膚瘙癢性皮疹前來就診。皮疹反覆出現，每次持續時間不超過 24 小時，未能找到明確的病因或誘發因素。

皮膚科檢查顯示：皮疹為界限清楚的風團，大小不一（<1 公分至 >8 公分），呈紅斑或皮膚色，周圍有紅暈。形態包括圓形、橢圓形、弧形、環形及蛇行狀，反映病灶在某些部位消退而在其他部位進展。皮疹瘙癢明顯，持續時間少於 24 小時，分佈廣泛。未能找到誘因。

根據定義，診斷為 慢性特發性蕁麻疹。患者對口服西替利嗪反應良好，並被建議避免可能加重病情的因素，如壓力、酒精及部分止痛藥。慢性特發性蕁麻疹通常持續 1–3 年後可自行緩解。

討論

急性與慢性蕁麻疹

急性蕁麻疹診斷標準：

1. 瘙癢
2. 風團持續 <24 小時
3. 無殘留色素沉著
4. 無脫屑
5. 病程 <6 週

約 15% 的急性蕁麻疹會演變為慢性蕁麻疹。兒童常伴隨全身症狀，如發燒、腸胃不適、關節痛。

急性蕁麻疹病因：

• 過敏性（IgE 媒介的肥大細胞致敏）：
  • 食物（如海鮮、螃蟹、雞肉）
  • 藥物（如青黴素、顯影劑）
  • 疫苗
  • 乳膠
• 非過敏性：
  • 病毒感染（兒童常見）
  • 藥物（嗎啡、阿司匹林、布洛芬）
  • 組胺（如腐敗魚類）

檢查：

• 詳細病史（食物、藥物、感染）
• RAST（血清特異性 IgE）或皮膚點刺試驗
• 藥物史回顧

急性蕁麻疹治療：

• 短期漸減劑量的口服類固醇
• 每日一次非嗜睡型抗組織胺
• 爽身粉或含薄荷的潤膚膏

慢性自發性蕁麻疹

病因分類：

1. 特發性（>50%）：可能與幽門螺旋桿菌相關
2. 免疫性（30–50%）：自身免疫蕁麻疹，常伴甲狀腺自身抗體或 IgG 抗體攻擊 FcεRI 或 IgE；可用自體血清皮膚試驗（ASST）檢測
3. 非免疫性/過敏性因素：
   • 嗎啡（直接作用於肥大細胞）
   • 阿司匹林/NSAIDs（影響白三烯途徑）
   • ACE 抑制劑（通過激肽途徑引起血管性水腫）

常見加重因素： 壓力、酒精、NSAIDs、ACE 抑制劑、病毒感染、月經。

治療原則：

• 避免誘因（壓力、酒精、NSAIDs、ACE 抑制劑）
• 急性發作：溫水淋浴、薄荷潤膚膏、口服氯苯那敏、短期類固醇
• 長期治療：非嗜睡型抗組織胺、H2 抗組織胺
• 頑固病例：抗組織胺合併治療、孟魯司特、環孢素

其他蕁麻疹類型

• 物理性蕁麻疹：皮膚劃痕症、延遲性壓力蕁麻疹、膽鹼能性蕁麻疹、冷性蕁麻疹、日光性蕁麻疹、熱性蕁麻疹、水源性蕁麻疹、震動性蕁麻疹、運動誘發性過敏/蕁麻疹。
• 血管性水腫：可單獨出現或伴隨蕁麻疹。