History

Fact Explanation
Dark discoloration of body folds including inner thighs, toe web spaces, axillae, submammary areas, etc (regions rich in heat and humidity). Corynebacterium minutissimum, is usually present as a normal human skin inhabitant, when it invades the stratum corneum (upper 1/3) under favorable conditions of heat and humidity, the organism proliferate, which promotes formation of a hyperkeratotic stratum corneum [1].
Pruritus of the affected regions. Due to thickening of the stratum corneum as a result of the infection [1].
History of excessive sweating associated with a warm climate. Increased humidity favors the growth of the causative organism [2].
History of diabetes mellitus. The immunocompromised state in diabetes promotes the occurrence of opportunistic infection [3].
References
  1. MONTES LF, MCBRIDE ME, JOHNSON WP, OWENS DW, KNOX JM. Ultrastructural study of the host-bacterium relationship in erythrasma. J Bacteriol [online] 1965 Nov, 90(5):1489-1491 [viewed 28 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC315839
  2. SARKANY IMRICH, TAPLIN DAVID, BLANK HARVEY. The Etiology and Treatment of Erythrasma1. J Investig Dermatol [online] 1961 October, 37(4):283-290 [viewed 28 July 2014] Available from: doi:10.1038/jid.1961.122
  3. LARKIN JG, FRIER BM, IRELAND JT. Diabetes mellitus and infection. Postgrad Med J [online] 1985 Mar, 61(713):233-237 [viewed 28 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2418179

Examination

Fact Explanation
Well-demarcated, brown-red macular patches in the affected regions of skin. The skin also presents with fine scales. These changes occur as a result of lichenification of the affected areas of skin secondary to the thickened stratum corneum and associated pruritus [1].
References
  1. RAJALAKSHMI R, THAPPA DM, JAISANKAR TJ, NATH AK. Lichen simplex chronicus of anogenital region: a clinico-etiological study. Indian J Dermatol Venereol Leprol [online] 2011 Jan-Feb, 77(1):28-36 [viewed 28 July 2014] Available from: doi:10.4103/0378-6323.74970

Differential Diagnoses

Fact Explanation
Tinea cruris. It also presents with a pruritic erythematous rash in the groin, but lesions show an active scaly palpable edge with central clearing, resulting in the appearance of annular patches of varying sizes [1].
Plaque psoriasis. It also presents in flexural areas as scaly lesions, but other features such as nail plate pitting, onycholysis and inflammatory polyarthritis also occur [2].
Seborrhoeic dermatitis. It manifests as red, sharply marginated lesions with greasy looking scales. But it tends to flare and remit spontaneously, and is prone to recurrence after treatment [3].
References
  1. MORIARTY B., HAY R., MORRIS-JONES R.. The diagnosis and management of tinea. BMJ [online] December, 345(jul10 1):e4380-e4380 [viewed 28 July 2014] Available from: doi:10.1136/bmj.e4380
  2. BAKER H. Psoriasis--clinical features. Br Med J [online] 1971 Jul 24, 3(5768):231-233 [viewed 28 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1798563
  3. NALDI L. Seborrhoeic dermatitis Clin Evid (Online) [online] :1713 [viewed 28 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3275327

Investigations - for Diagnosis

Fact Explanation
Wood's light examination of erythrasma lesions revealing coral-red fluorescence of lesions. Excess Copro III synthesis by Corynebacterium leads to accumulation of porphyrin in cutaneous tissue, which fluoresces a coral-red colour when exposed to Wood’s light [1].
Microscopic examination of scales using the Methylene blue stain, which is used to highlight both the fungal spores of pityriasis versicolor and the curved or club-shaped bacterial rods of C. minutissimum. This can be used as a single method to diagnose both conditions at the same time [2]. It should be noted that these 2 diseases can co exist.
References
  1. YASUMA A., OCHIAI T., AZUMA M., NISHIYAMA H., KIKUCHI K., KONDO M., HANDA H.. Exogenous coproporphyrin III production by Corynebacterium aurimucosum and Microbacterium oxydans in erythrasma lesions. Journal of Medical Microbiology [online] December, 60(7):1038-1042 [viewed 29 July 2014] Available from: doi:10.1099/jmm.0.027276-0
  2. PADILHA-GONçALVES ANTAR. A single method to stain Malassezia furfur and Corynebacterium minutissimum in scales. Rev. Inst. Med. trop. S. Paulo [online] 1996 August [viewed 29 July 2014] Available from: doi:10.1590/S0036-46651996000400011

Investigations - Screening/Staging

Fact Explanation
Fasting blood glucose levels. The immunocompromised state in diabetes promotes the occurrence of opportunistic infection [1].
References
  1. LARKIN JG, FRIER BM, IRELAND JT. Diabetes mellitus and infection. Postgrad Med J [online] 1985 Mar, 61(713):233-237 [viewed 28 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2418179

Management - General Measures

Fact Explanation
Educate on personal hygiene. Personal cleanliness produces a significant reduction in the carriage of diphtheroids in the skin [1].
References
  1. SOMERVILLE D. A.. Erythrasma In Normal Young Adults. Journal of Medical Microbiology [online] 1970 February, 3(1):57-64 [viewed 29 July 2014] Available from: doi:10.1099/00222615-3-1-57

Management - Specific Treatments

Fact Explanation
Erythromycin. Dose: 250 mg 4 times a day for 14 days given orally. Inhibits bacterial growth by inducing dissociation of peptidyl t-RNA from ribosomes, resulting in RNA-dependent protein synthesis to come to a halt [1]. C. minutissimum shows increased susceptibility to the drug.
Illumination of lesions (80 J/cm2) by red light (broad band, peak at 635 nm). It utilizes reactive oxygen species produced by a non-toxic dye or photosensitizer molecule in the presence of low intensity visible light to kill microbial cells [2].
References
  1. TENSON TANEL, LOVMAR MARTIN, EHRENBERG MåNS. The Mechanism of Action of Macrolides, Lincosamides and Streptogramin B Reveals the Nascent Peptide Exit Path in the Ribosome. Journal of Molecular Biology [online] 2003 July, 330(5):1005-1014 [viewed 29 July 2014] Available from: doi:10.1016/S0022-2836(03)00662-4
  2. KHARKWAL GB, SHARMA SK, HUANG YY, DAI T, HAMBLIN MR. Photodynamic Therapy for Infections: Clinical Applications Lasers Surg Med [online] 2011 Sep, 43(7):755-767 [viewed 29 July 2014] Available from: doi:10.1002/lsm.21080