1Department of Dermatology, Alcalá la Real High Resolution Hospital, Jaén, Spain; 2Department of Dermatology, University Hospital Complex of 
Granada, Granada, Spain
*Corresponding Author e-mail: gonzaloblascomorente@gmail.com

فحص تألقي بلون أمحر مرجاين لرتسبات الوذح اجللدي
غونزالو بال�صكو-مورينتى، �صلفادور اأريا�ض-�صانتياغو، اإ�رضائيل برييز-لوبيز، اأنطونيو مارتينيز-لوبيز

Coral-Red Fluorescence of Erythrasma Plaque
*Gonzalo Blasco-Morente,1 Salvador Arias-Santiago,2 Israel Pérez-López,2 Antonio Martínez-López2

A 50-year-old man presented to the Department of Dermatology, University Hospital Complex of Granada, Granada, 
Spain, in 2015 with a slightly pruritic rash on the 
left groin, which he had had for two years. He had 
attended the hospital previously and been diagnosed 
with eczema and tinea cruris. This had been 
treated with topical steroids and antifungal drugs 
(methylprednisolone and sertaconazole) for several 
months without improvement. A physical examination 
of the patient showed a diffuse, brownish, well-defined, 
scaly plaque in the left inguinal region [Figure 1A]. A 
potassium hydroxide preparation of tissue scrapings 
was negative for fungal elements or cultures. The coral-
red fluorescence of the plaque under a Wood’s lamp 

(WL) examination was characteristic of erythrasma 
[Figure 1B]. The patient was treated with 500 mg of 
oral erythromycin every 12 hours for 14 days, with 
progressive healing observed over three weeks.

Comment

Erythrasma is a localised and chronic skin infection 
caused by Corynebacterium minutissimum.1–3 It 
appears as patches that are either asymptomatic and 
well-defined or irregular in shape and size and red/
brown in colour.3–5 The diagnosis is usually clinical, 
but a WL examination can show characteristic fluor-
escence due to coproporphyrin III produced by the 
bacteria.2,3 The WL emits ultraviolet A radiation with 

Figure 1A & B: A: Diffuse, brownish, well-defined, scaly plaque in the left inguinal region of a 50-year-old man. Note the 
‘cigarette paper’ appearance. B: Wood’s light skin examination of the plaque showing bright coral-red fluorescence 
characteristic of erythrasma.

interesting medical image 

Sultan Qaboos University Med J, August 2016, Vol. 16, Iss. 3, pp. e381–382, Epub. 19 Aug 16
Submitted 10 Jan 16
Revision Req. 1 Feb 16; Revision Recd. 1 Mar 16
Accepted 13 Mar 16 doi: 10.18295/squmj.2016.16.03.023



Coral-Red Fluorescence of Erythrasma Plaque

e382 | SQU Medical Journal, August 2016, Volume 16, Issue 3

References
1. Klatte JL, van der Beek N, Kemperman PM. 100 years of Wood’s 

lamp revised. J Eur Acad Dermatol Venereol 2015; 29:842–7. 
doi: 10.1111/jdv.12860.

2. Blasco Morente G, Martínez Peinado C, Martínez García E, 
Tercedor Sánchez J. [Wood’s lamp in congenital erythropoietic 
porphyria]. An Pediatr (Barc) 2014; 81:403–4. doi: 10.1016/j.
anpedi.2014.01.005. 

3. Wilson BB, Wagenseller A, Noland MM. An atypical present-
ation of erythrasma. J Am Acad Dermatol 2012; 67:e217–18. 
doi: 10.1016/j.jaad.2012.04.004. 

4. Chodkiewicz HM, Cohen PR. Erythrasma: Successful treat-
ment after single-dose clarithromycin. Int J Dermatol 2013; 
52:516–18. doi: 10.1111/j.1365-4632.2011.05005.x. 

5. Holdiness MR. Erythrasma and common bacterial skin 
infections. Am Fam Physician 2003; 67:254.

wavelengths between 320–400 nm and is useful in the 
diagnosis of disorders of pigmentation, skin infections 
(such as erythrasma) and porphyrias.2 However, 
microscopic examinations (e.g. Gram staining of an 
epidermis scraping to reveal Gram-positive filaments 
and rods) and cultures on different types of media (e.g. 
20% fetal bovine serum, 2% agar and 78% tissue culture 
medium #199) may be required in certain cases.4,5 A 
potassium hydroxide preparation of tissue scrapings 
can rule out concomitant infections, especially in 
patients with interdigital involvement.4 The differential 
diagnosis of erythrasma includes candidiasis, psoriasis 
and dermatophytosis.1–5 The most effective treatment 
is 500 mg of erythromycin twice daily for 14 days, with 
cure rates as high as 100%; however, other treatments 
with topical antibiotics and antifungals have also 
demonstrated good responses.1–5

http://dx.doi.org/10.1111/jdv.12860
http://dx.doi.org/10.1016/j.anpedi.2014.01.005
http://dx.doi.org/10.1016/j.anpedi.2014.01.005
http://dx.doi.org/10.1016/j.jaad.2012.04.004
http://dx.doi.org/10.1111/j.1365-4632.2011.05005.x