Wrestling a scaly, spreading rash

Issue: March 2012

The 18-year-old star of the local high school’s wrestling team presents to your office with a mildly pruritic rash that started on his back and has spread slowly to the chest, abdomen and proximal extremities. The rash notably spares his scalp, face and genitalia. He first noticed the rash in the summer because the spots made his tan “blotchy.” He has no contact with animals — save for the occasional prank played on the rival high school’s mascot.

Andrew C. Krakowski

On physical exam, you see numerous pinkish-brown, well-demarcated, round-to-oval, flat-topped papules and plaques scattered diffusely over the trunk with extension to the inferior-posterior neck, superior abdomen and proximal extremities. The lesions coalesce somewhat over the shoulders and superior back. Light lateral stretching of the affected skin tends to produce an overlying fine, “dust-like” scale confined to the discrete lesions.

All of these statements are false, except:

A. A traditional fungal culture of the lesions is your best bet for making the diagnosis.

B. This condition is usually associated with underlying immunologic deficiencies.

C. The condition tends to affect all races and genders equally but is more common in certain geographic locations.

D. Oral antifungals are the only effective treatment for this condition.

E. We need to know more about that rival school’s mascot, as this is likely a zoonotic infection.

Diagnosis: Tinea versicolor (also known as pityriasis versicolor).

Tinea versicolor (TV) is an extremely common, benign skin disorder caused by the dimorphic, lipophilic organisms in the genus Malassezia (formerly known as Pityrosporum). This organism is part of the normal skin flora (therefore, Answer E is false) and can be found on patients with clinical disease in both the spore and the hyphal forms. Infection is limited to the stratum corneum, the uppermost portion of the epidermis.

The name versicolor itself means “several colors,” a fact that is reflected in the range of colors (from white to red to brown) assumed by TV lesions. Some lesions may be hypopigmented because Malassezia produces azelaic acid, which is a dicarboxylic acid that inhibits the dopa-tyrosinase reaction necessary for melanocyte pigment formation (this acid is currently marketed as a therapy for acne-induced hyperpigmentation). Conversely, some lesions are hyperpigmented because Malassezia can also induce an enlargement of the melanosomes made by melanocytes residing in the basal layer of the epidermis.

TV occurs worldwide and is more frequently seen in areas with higher temperatures and higher relative humidities. Some patients appear to have a genetic predisposition/positive family history. The exact incidence of TV is difficult to predict because many affected individuals may not seek medical attention. The alteration in skin pigmentation may appear to make TV more common in darker-skinned patients; however, the incidence appears to be the same across all races and genders (thus, Answer C is true). In the United States, where the incidence is estimated to be 2% to 8%, TV is most common in adolescents and young adults — possibly in relation to the sebum-rich local environments that these patients afford the lipophilic Malassezia.

Figure 1 and 2 illustrate the rash.

Figure 2

While most cases of TV occur in healthy individuals with no underlying immunologic deficiencies (making Answer B false), chronically recurring or recalcitrant disease should raise consideration for possible immunosuppression, malnutrition or endogenous/exogenous Cushing’s syndrome.

The differential diagnosis of TV includes post-inflammatory hypo- or hyperpigmentation, pityriasis alba, vitiligo, and confluent and reticulated papillomatosis (Gougerot-Carteaud syndrome). In contrast to TV, which is hypopigmented, vitiligo presents with discrete macules and patches defined by true depigmentation (positive fluorescence with Wood’s lamp examination); often, these lesions are present over bony prominences, in areas of friction and around orifices. Pityriasis alba presents with hypopigmented macules and patches, but these lesions are mostly limited to the face; there is also typically a history of atopic dermatitis.

The diagnosis of TV is usually made clinically based on the characteristic presentation. Malassezia is extremely difficult to grow in laboratory culture, requiring special cultures enriched with fatty acids. Likewise, it is nearly ubiquitous as normal skin flora, making a positive culture almost irrelevant (therefore, Answer A false). Instead, the diagnosis may be confirmed by a potassium hydroxide (KOH) wet-mount of cutaneous scrapings. Microscopic examination reveals the characteristic “spaghetti and meatballs” or “ziti and meatballs” pattern, representing short fungal hyphae and spores in grape-like clusters.

Figure 3 demonstrates the positive “stretch test” in which the skin is gently stretched laterally to better reveal the overlying scale.

Figure 4 is a ragingly positive KOH demonstrating hyphal forms.

Treatment

Treatment of TV is straightforward, with education forming the keystone of any management plan. Extreme diet alterations have not demonstrated any sort of success and should be avoided. Patients should understand that TV might recur and that skin pigment changes may take months to revert to normal; sun avoidance/protection is the best way to minimize contrast between affected and normal skin.

Topical preparations are usually very effective (making Answer D false). Selenium sulfide 2.5% shampoo or lotion is an inexpensive and readily available therapy that can be used safely in children and adolescents. Typically, it is applied to affected areas of the skin for about 10 minutes and then washed off; this process is repeated once a day for about 2 weeks.

For chronic maintenance, this process can be repeated every other week or during the first week of each month. Ketoconazole 2% shampoo, similarly used, is also very effective, though it may be difficult to obtain at the pharmacy level. Clotrimazole 1% cream or ketoconazole 2% cream applied directly to the lesions can be used once to twice daily for 2 weeks with good success. Terbinafine 1% spray is another option for covering wide surface areas or difficult to reach areas of skin.

Oral antifungal therapy for TV is not without risk, so the decision to treat this otherwise benign condition with an oral agent warrants a thorough discussion of the risks and benefits. Typically, oral agents are reserved for patients with severe TV, recurrent/recalcitrant disease or when compliance is a true issue. A variety of oral antifungal agents have been reported for this condition, including ketoconazole, fluconazole (Diflucan, Pfizer), itraconazole (Sporanox, Janssen/Ortho Biotech) and terbinafine (Lamisil, Novartis).

Ketoconazole "single-dose" therapy (400 mg) or ketoconazole 200 mg daily for 10 to 14 days are both popular and effective treatment strategies. Fluconazole single-dose therapy (400 mg) or fluconazole 150 mg to 300 mg dosed weekly for 2 to 4 weeks are also effective options that may be less hepatotoxic than other oral antifungals. Itraconazole single-dose therapy (400 mg) was found to be as effective as itraconazole 200 mg daily for 7 days. Results may be enhanced by instructing patients to take their oral medication and participate in physical activity to promote secretion of the drug onto the skin via sweating.

References:

Balwada RP. Indian J Dermatol Venereol Leprol. 1996;62:298-300.

Gupta AK. Expert Opin Pharmacother. 2005;6:165-178.

Nagpal VB. Indian J Dermatol Venereol Leprol. 2003;69:287-288.

Yazdanpanah MJ. Mycoses. 2007;50:311-313.

Andrew C. Krakowski, MD, completed a residency in pediatrics at Johns Hopkins Medical Institute and a residency in dermatology at University of California, San Diego. He is currently a fellow in pediatric dermatology at Rady Children’s Hospital, San Diego. Catch him on Outdoor Channel as the host of boonDOCS Wilderness & Travel Medicine Show (email:dr.k@boonDOCSmedicine.com). Disclosure: Dr. Krakowski reports no relevant financial disclosures.