Slide 1: Test Yourself! A Wood’s lamp emits primarily UV-A spectrum light, and very little visible light. It is used in medicine and other industries to detect fluorescent substances. Which of the following conditions can a Wood’s lamp be helpful in diagnosing? A) Porphyria cutanea tarda. B) Tuberous sclerosis. C) Ethylene glycol toxicity. D) All of the above.
Slide 2: D) All of the above. Collagen and porphyrins are two substances that absorb light in the UV spectrum, but subsequently emit light in the visible spectrum. In disorders characterized by hypopigmentation, such as tuberous sclerosis, the absence of melanin in the epidermis of ash-leaf lesions creates a window revealing dermal collagen, which fluoresces. In porphyria cutanea tarda, the patient’s urine will turn a pinkish color when placed under a Wood’s lamp.
Slide 3: Ethylene glycol toxicity presents with altered mental status, high anion gap metabolic acidosis, and renal failure due to the accumulation of calcium oxalate crystals in the renal tubule. While ethylene glycol and its metabolites are not fluorescent, exposure to ethylene glycol from ingestion of antifreeze will result in Wood’s lamp-positive urine due to the presence of fluorescent additives in most antifreeze formulas.
- Asawanonda P, Taylor CR. Wood’s light in dermatology. Int J Dermatol. 1999 Nov;38(11):801-7. PMID 10583611
- Winter ML, Ellis MD, Snodgrass WR. Urine fluorescence using a Wood’s lamp to detect the antifreeze additive sodium fluorescein: a qualitative adjunctive test in suspected ethylene glycol ingestions. Ann Emerg Med. 1990 Jun;19(6):663-7. PMID 2344083
Tags: dermatology, ethylene glycol, porphyria, toxicology, tuberous sclerosis, Wood's lamp