Erythema ab Igne

Erythema ab igne and Laptop Computers

Dermatologic eruptions (AKA rashes) exist on such an interesting spectrum – from unexciting to emergent. We’ve previously discussed my general approach to rashes (and occasional disdain for them). We have also reviewed our need to maintain vigilance for the potential emergent issues balanced with the reality that most are benign (ex, Erythema Multiforme, Urticaria, Eczema Herpeticum, Hand-Foot-Mouth Disease, Staph Scaled Skin, ITP), but the one interesting aspect of rashes is that they may be just the clue we need to solve the riddle. Pyoderma Gangrenosum is a good example. Let’s take a minute to review another interesting clue – Erythema ab Igne:

Erythema ab igne: Basics

  • Erythema ab igne = “redness of the fire
    • Historically noted to have occurred after exposure to low-grade infrared radiation at temperatures below the level that would lead to a thermal burn. [Salvio, 2016]
    • Higher temperatures increase risk.
    • Prolonged exposure increase risk.
  • It is a Clinical Diagnosis. [Gmuca, 2018; Arnold, 2010]
    • Has a Reticulated (“lacy”, Web-like, Geographic) pattern.
    • Initially (after less exposure),
    • With prolonged exposure,
      • Becomes more permanent / persistent
      • Becomes hyperpigmented and violaceous.
      • May lead to cutaneous atrophy and telangiectasias.
  • Underlying pathology thought to include: [Gmuca, 2018]
    • Local hemostasis and vasodilation
    • Overtime, red blood cells extravasate into the dermis.
    • Degraded RBCs deposit hemosiderin into the dermis, staining it.
  • Can have associated Malignant Progression with persistent exposure.
    • Chronic exposure can lead to malignant transformation. [Salvio, 2016; Sigmon, 2013; Arnold, 2010]
      • Squamous Cell Carcinoma is the most common.
      • Merkel Cell Carcinoma can also occur.
      • Malignant transformation is delayed by multiple decades.
    • Good reason for us to encourage avoidance of prolonged exposure now!

Erythema ab igne: Associated Causes

  • Any source of radiant heat that isn’t associated with thermal burn.
  • Typically over a prolonged exposure. [Salvio, 2016]
  • Historically, associated with: [Salvio, 2016; Sigmon, 2013]
    • Charcoal braziers
    • Peat fires
    • Kilns for pottery, metal working, glass blowing, etc
  • Today, more typically seen with: [Salvio, 2016; Sigmon, 2013]
    • Pain Relief Therapies:
      • Electric blankets
      • Hot water bottles
      • Prolonged Hot Showers
      • Why we should advise not exceeding 15-20 min of continuous application of heat (ex, “don’t go to sleep with your electric blanket).
    • Heated Car Seats (when luxury bites you in the butt!)
    • Portable Space Heaters
    • Saunas, Hot Tubs, Hot Baths
    • Mobile Phones
    • Computer Laptops [Arnold, 2010]
      • Computer can produce temperatures up to 111 F (44 C).
      • Highest heat source is usually not evenly distributed, so may affect one side more than the other.
      • Optical Drive often on left side, so left leg more affected.
      • Placing laptop on lap, actually can obstruct the heat dissipation mechanisms, leading to higher temperatures.

Erythema ab igne: May Look Like:

  • Livedo Reticularis [Gmuca, 2018]
    • Physiologic – “Cutis Marmorata” – due to cold exposure and resolves with warming
    • Pathologic – does not resolve with warming; may be congenital or acquired (due to altered blood flow).
  • Autoimmune Disorders (ex, Cutaneous Vasculitis, Systemic Lupus) [Gmuca, 2018]
  • Infections (ex, Mycoplasma pneumonia, Parvovirus B19, Rheumatic Fever) [Gmuca, 2018]
  • Hematologic (ex, Antiphospholipid Antibody Syndrome, DVT) [Gmuca, 2018]

Moral of the Morsel

  • Laptops are not meant for your lap! The heat created can lead to erythema ab igne. Use a Lap Table, or a Table, or a buffer of some kind.
  • Stop it now, and avoid the potential Cancer 30 years from now. It is useful to know that it is benign today… but encourage a change in behavior to avoid future problems.


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Salgado F1, Handler MZ1, Schwartz RA1. Erythema ab igne: new technology rebounding upon its users? Int J Dermatol. 2018 Apr;57(4):393-396. PMID: 28369761. [PubMed] [Read by QxMD]
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Steadmon MJ1, Riley KN. Erythema ab igne: a comeback story. J Pediatr. 2013 Dec;163(6):1789. PMID: 24011766. [PubMed] [Read by QxMD]
Sigmon JR1, Cantrell J, Teague D, Sangueza O, Sheehan DJ. Poorly differentiated carcinoma arising in the setting of erythema ab igne. Am J Dermatopathol. 2013 Aug;35(6):676-8. PMID: 23872874. [PubMed] [Read by QxMD]
Arnold AW1, Itin PH. Laptop computer-induced erythema ab igne in a child and review of the literature. Pediatrics. 2010 Nov;126(5):e1227-30. PMID: 20921068. [PubMed] [Read by QxMD]
Sean M. Fox
Sean M. Fox

I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renowned educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.

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