Makindo Medical Notes

🔥 Introduction

• Erythema ab igne (Latin: “redness from fire”) is a chronic, reticulated, hyperpigmented dermatosis caused by repeated or prolonged exposure to infrared radiation or heat insufficient to cause an acute burn.
• Classically described as the “toasted skin syndrome.”
• More common in women than men, reflecting both cultural practices (use of heat pads) and occupational exposure.

⚠️ Causes

• Chronic use of hot water bottles or heating pads (e.g., for back pain or menstrual cramps).
• Prolonged exposure to domestic heat sources: space heaters, fireplaces, or wood-burning stoves.
• Occupational hazard in bakers, foundry workers, and kitchen staff exposed to high heat.
• Modern variant: “Laptop thigh” syndrome from resting hot laptops on bare skin for extended periods.

🩺 Clinical Manifestations

• Symptoms are usually mild — patients may describe burning, itching, or warmth at the site.
• Skin findings: a reticular, erythematous or brownish pigmentation, resembling livedo.
• With chronic exposure: epidermal atrophy, bullae, or ulceration can develop.
• ⚠️ Rare but important: long-standing erythema ab igne may undergo malignant transformation (squamous cell carcinoma or Merkel cell carcinoma).

🔍 Diagnosis

• Primarily a clinical diagnosis: based on the characteristic reticular pattern and a clear history of heat exposure.
• Laboratory tests are not useful.
• Biopsy: reserved for atypical cases, ulcerated lesions, or suspicion of malignancy.
• Differentials include:
  • Livedo reticularis: due to vascular obstruction or vasculitis, often reversible with warming.
  • Livedo racemosa: irregular net-like pattern, associated with autoimmune/vasculitic conditions.

💊 Treatment and Prognosis

• Remove the heat source — the most critical step; pigmentation may fade over months.
• Topical treatments: Tretinoin (stimulates skin turnover) or hydroquinone (lightening agent) may improve pigmentation.
• Patient education: advise on safe alternatives for warmth (e.g., warm clothing, not direct heat).
• Follow-up: essential for chronic cases due to malignant transformation risk.
• Prognosis is generally favourable if exposure is discontinued, but irreversible pigmentation may persist if longstanding.

💡 Teaching pearl: If you see a chronic, reticulated hyperpigmentation on the shins, back, or thighs — always ask about heat exposure. Think of “toasted skin syndrome” before embarking on complex autoimmune work-ups!