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A Teenage Boy with an Unsightly Rash

A Teenage Boy with an Unsightly Rash

  • Your first patient today is an 18-year old who has been missing school because he is self-conscious about the rash he has had for the past 3 to 4 months. The rash is most prominent on his back , chest, and arms (the pictures of the arms is classical). He attributes the rash to “acid” because “I drink too many sodas.” He has stopped drinking soda for the past 8 weeks, but the rash persists. He comes to you for help...
  • He is a typical teenager with no significant health problems in the past. He denies: smoking cigarettes/marijuana, use of illegal substances, sexual activity. He has not put anything on his skin nor has he had any prior skin problems. The rash became more apparent as he obtained his “usual summer tan.”
  • Note the slightly scaly, hypopigmented macular lesions over back and shoulders.
  • Hypopigmented macular lesions on the arm.
  • Hypopigmented macular lesions on the arm.
  • Classic image: Hypopigmented macular lesions on the arm.
  • Differential diagnosis: Post-inflammatory hypopigmentation, vitiligo, tinea versicolor, lichen sclerosis et atrophicus (LS&A), pityriasis alba, nevus depigmentosus, guttate hypomelanosis, tuberous sclerosis, (confetti-like lesions), pityriasis lichinoides chronicus
  • A hypopigmented or hyperpigmented or erythematous macular eruption. Macules frequently coalesce into larger patches. There is a characteristic fine scale that is adherent, but does not bleed with scraping.
  • Organism – from the genus Malassezia (more recently the nomenclature refers to it as Pityrosporum) A lipophlic yeast that is endogenous on the skin, but increases in adolescence when the sebacious glands increase in activity. Is normally in saprophytic yeast form (referred to as Pityrosporum orbiculare). When it converts to the mycelial form (Malassezia furfur) it is capable of causing clinical disease. Pityrosporum or Malassezia? It all depends on your reference! Concentrate on the correct diagnosis; the taxonomists will work out the nomenclature!
  • Lesions can be anywhere, but predominate on the trunk. Not infrequently found in the scalp, so think of it as a possibility for patients with dandruff. Rash is exacerbated by high heat and humidity but can also worsen with: Immunosuppression, systemic steroids, sweaty skin, greasy skin.
  • How can Malassezia furfur induce both hypopigmentation and hyperpigmentation? Hypopigmentation is explained by the fact that the organism produces dicarboxylic acid which inhibits the tyrosinase activity of melanocytes…which results in diminished melanin production. Hyperpigmentation may be the result of post-inflammatory hyperpigmentation.These changes are most obvious in dark-skinned people.
  • Hypopigmented tinea versicolor on dark skin.
  • Making the diagnosis: do you still have a microscope? Scrape the scale, place a drop or two of KOH on the slide, and look for the characteristic “spaghetti and meatball” forms under the microscope. The meatballs are the yeast forms The pieces of spaghetti are the short hyphae. Cultures are expensive and require a source of lipid to grow…Wood’s lamp will usually fluoresce the affected areas as a yellow color.
  • Characteristic Findings: “Spaghetti and Meatballs”
  • Tinea versicolor, topical treatment: Selenium sulfide (2.5%) lotion or shampoo: Apply every day x7 days; then every week x4 weeks; then every month x12 months (use as a body wash). Ketoconazole shampoo: Apply for 5 minutes rinse off - one time cure rate is ~70%. Use 3 times - cure rate = 73%. Azole creams – apply twice daily for 14 days. Allylamine creams – same as azoles. Consider that the topical creams can be expensive - $13- $14/ small tube… So, what is a better way?
  • Tinea versicolor: systemic treatment: Ketoconazole tablets: 400 mg taken at once; repeat in one week and at 15 days. Problem is ~33.3 % relapse rate. Fluconazole: 400 mg single dose / repeat monthly prn. Itraconazole: 200 mg daily for 5-7 days.
  • A clinical pear for tinea versicolor that really works: A popular regimen for treatment or prevention of tinea versicolor is a single 400 mg dose of ketoconazole. The dose is taken with orange juice or a carbonated beverage one hour prior to engaging in a sweat- producing activity. The sweat should be allowed to dry on the skin, and showering should be delayed for several hours. This method has not been tested in clinical trials.
  • Ketoconazole and sweat: The beneficial effect of sweat on ketoconazole for tinea versicolor is supported by pharmacokinetic research. Within one hour of its appearance in blood, ketoconazole reaches the skin via eccrine sweat. (Eccrine, the most numerous kind of sweat gland, produces cooling sweat. The less numerous apocrine sweat glands produce odor-causing sweat.)
  • Ketoconazoel and sweat; Once on the skin, ketoconazole binds to surface lipids and keratin as the sweat dries. Ketoconazole is also deposited on skin by sebum, but this occurs slowly over three to four weeks. Ketoconazole requires an acidic environment for optimal absorption. Absorption is improved by concurrent intake of food or a beverage with a pH less than three. Drugs that decrease gastric acidity reduce absorption. In combination with selenium sulfide the practitioner is actually “treating from inside and out.”

The teen is otherwise healthy. See what you make of the history and images. A full discussion of the diagnosis and effective treatment follows the differential--and your diagnosis.


Single dose ketoconazole for tinea versicolor. The Prescribers Letter. February 2004; Vol. 20 No. 200208.

American Academy of Dermatology. Tinea versicolor. Accessed on July 29, 2015 and available at:

Burkhart CG. Tinea versicolor. Accessed on July 29, 2015 and available at

Wahab MA, Ali ME, Rahman MH, et al. Single dose (400 mg) versus 7 day (200 mg) daily dose itraconazole in the treatment of tinea versicolor: a randomized clinical trial. Mymensingh Med J. 2010;19:72-76.

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