#82: Fungi Fun! An In-Depth Look at Tinea Infections

April 12, 2023 | By Sam Masur

Audio

Summary: 

Calling all fungi fighters! It’s time to level up your dermatophyte identification and treatment skills. Learn to take down tinea like a dermatologist in this pearl-packed episode with the great Dr. Craig Rohan. Listen now to become a skin savior, up your azole advocacy, and rule out those pesky mycosis mimickers!

Tinea Pearls

1. Maintain an index of suspicion for tinea incognito—these tinea infections will have an irregular appearance due to the prior use of topical steroids.
2. A fungal culture is easy to do and well worth it! If you aren’t able to remove scale to culture, reconsider the diagnosis. 
3. Differentiate tinea corporis from granuloma annulare by feeling the lesion—while both are elevated, scaliness or rough areas are indicative of tinea.
4. Topical azoles are generally first line for tinea corporis—ketoconazole is an excellent choice because it also has anti-inflammatory properties.
5. Oral azoles are generally first-line for tinea capitis and onychomycosis. Consider pulse therapy (e.g., medicating for one week per month) in order to get more “bang for your buck” with medication administration. Watch out for P450 drug interactions.
6. One treatment option for tinea versicolor is to have the patient take an oral azole, then exercise (to build up sweat), and then wait 6-8 hours before showering. This allows the medication to enter and linger in sweat glands and may be more effective than topical medication or usual administration of oral medication.

Tinea Show Notes

Pathophysiology & Epidemiology

• Tinea is a dermatophyte condition (NOT yeast), which has implications for treatment options (see below). 
• There is an increased prevalence in kids with eczema due to impaired skin barrier function.
• Look for environmental triggers (e.g., pets). Many species of dermatophytes can be passed from animals. 
• Plant and soil dermatophyte species cause more “exuberant” reactions. The most extreme cases will appear as bullous or vesicular tinea. 
• Kerion occurs when recurrent tinea capitis triggers a  type IV hypersensitivity reaction to dermatophytes—this actually looks similar to poison ivy under a microscope. (Grijsen & de Vries, 2017)
• The prevalence of various tinea infections seems to vary based on genetic factors (Nguyen et al., 2020). There may be an increased susceptibility in patients with an Rh+ blood type (Al-Daamy et al., 2019). 

Presentation

Tinea corporis

• Typically asymptomatic, can have some irritation/pruritus.
• Usually will have central clearing: look for a scaly advanced edge and a center where the skin is more recovered or even completely healed.
• Feels rough to touch – you should be able to detect the leading edge of the lesion with touch alone.

Tinea capitis

• Almost always has some degree of hair loss. 
• May have scaling or inflammatory component.

“Tinea incognito” 

• This occurs when use of topical steroids changes the appearance of a tinea infection (Paloni et al., 2015); have low threshold to include this on a differential for various irregular lesions.
• Often will have a polycyclic presentation (clover-like appearance), which happens because the edge of the tinea lesion was able to grow.
• Margins are typically less discrete/raised.
• May include multifocal areas (spread over multiple parts of body)—more common in adults.

Evaluation/Diagnosis

• Culture is very helpful, especially when susceptibility information can be obtained. This is particularly important in patients who take medications that may interact with antifungals and in cases of tinea capitis where there is a concern for scarring/alopecia. Culture can usually be sent with a scraping in a sterile urine cup or routine culture swab.
• KOH or chlorazol black (slightly easier to visualize) staining is a helpful in-office procedure for making/reinforcing a diagnosis.

Differential Diagnosis 

Granuloma annulare:

• Like tinea corporis, this is common in kids and also presents with central clearing.
• Often produces a “prettier ring” than tinea corporis.
• Occurs due to an expansion of dermal cells (macrophages in the dermis ‘engulf’ collagen and reproduce a scar-like response under the skin).
• The top surface of the skin remains smooth—if there is nothing to scrape for a culture consider this diagnosis instead. In the words of Dr. Rohan “if sending a culture would entail blood” strongly consider the possibility of granuloma annulare. 
• Follows a koebnerization pattern—often occurs in area(s) of pressure/trauma/friction (e.g., elbows/knees/armpits/back of wrists/shins). 
• Treat with medium-high strength topical steroids. More severe cases may require hydroxychloroquine or intralesional steroids. Phototherapy is also a treatment option used for adult patients.

Nummular eczema: 

• Highly pruritic.
• Relatively treatment resistant.
• Look for Hanifin and Rajka criteria for eczema, although this can also occur in patients with no prior history of eczema.

Psoriasis: 

• Fairly rare in younger kids, may start seeing more in teenagers.
• Solitary round plaque.
• Typically no central clearing, very scaly.
• Autoimmune—keratinocytes grow in an uncontrolled/unregulated fashion. A patient may grow “one month’s worth of keratin” in a single day!

Pityriasis/tinea versicolor: 

• Yeast form, not a dermatophyte.
• Polycyclic small thin circles with very little scaling.
• No central clearing.
• Typically treat with azoles (including shampoo formulations for more widespread presentations). Can also use selenium sulfide shampoo but this is not fungicidal (it works by “making yeast slippery”).

Management

Topical Medications 

Medication Selection

• Azoles: This is usually the first-line for treatment. Most have generic formulations and are relatively affordable.  Mechanism of action is comparable to beta-lactam antibiotics (they work by punching holes in the cell walls of fungi).
  • Ketoconazole also has 5-lipoxygenase activity which has anti-inflammatory properties (this is why the shampoo is useful for psoriasis). This is Dr. Rohan’s “go to” azole.
  • Newer azoles mainly differ in terms of the size of the molecule, allowing an application to last longer. In Dr. Rohan’s opinion, this is not worth the significant increase in price. 
• Allylamines/Terbinafine: Relatively good option. Does have holes in coverage spectrum (mainly an issue for systemic use)—candida is intrinsically resistant. 
• Note that tinea infections are NOT yeast; thus medications like nystatin are unlikely to be effective and use of them can delay proper treatment.
• Gentian violet: Classic treatment for older adults with diabetes for toe web space infections. Dr. Rohan regards this as a “scorched earth” approach, as it works well but can cause secondary irritation. He advises that it is usually not needed in pediatrics. 
• Historic note: tinea infections used to be treated with in-office radiation! This is not used anymore due to skin cancer risk. 

Prescribing Considerations 

• Dr. Rohan typically writes instructions to continue to use topical medications until 2-3 weeks after clearance and to restart for a few weeks if there is any hint of recurrence. 
• There is no known significant risk for resistance to topical antifungals.
• While tinea capitis treatment generally requires oral antifungals (see below), adjunctive shampoo use can improve clearance. Dr. Rohan advises 3% salicylic acid shampoo (which removes scale allows better penetration of topical medication) alternating with ketoconazole shampoo. Warn patients that mild irritation is normal and is usually a sign that the medication is working.
• A reasonable approach when diagnosis is uncertain: Start ketoconazole twice daily for 2-3 weeks while awaiting culture results (if able). If the lesion does not improve after 2-3 weeks, continue the ketoconazole AND add a mid-potency topical steroid. If the lesion is still not improved, consider a dermatology consult.

Oral Therapies 

• Hair-bearing areas and nails have fairly poor penetration with topical antifungals (although if adherence is excellent, topical ciclopirox can work for kids with onychomycosis). Oral medications are also reasonable when large areas are affected or in patients with comorbidities (including atopic dermatitis).
• Azoles (most commonly fluconazole and itraconazole) are generally a safe, first-line option but in rare occasions can cause idiosyncratic liver failure. This is more common with oral ketoconazole (rarely used for this reason). Monitor for P450 interactions. 
  • Consider pulsed therapy! Have the patient take the medication daily for one week per month for three to five months. This works because the medication “sits in the skin”. (Salunke et al., 2020). 
  • Expert approach: For more extensive tinea versicolor or corporis infections, have the patient take 100-200 mg of itraconazole, then exercise (to build up a sweat), then “wallow” in the sweat for 6-8 hours before showering. This will allow the treatment to penetrate follicles which is far more effective than topical or regular oral treatment. Repeat 1-2 weeks later. 
  • For tinea capitis consider adjunctive shampoo—see above.
• Griseofulvin: Used more in adults, usually selected for medically-complex patients with risk for drug interactions. Typically has more side effects than azoles (Woodard et al., 2021) and is photosensitizing (significant risk for sunburn!).
• Terbinafine: First line for onychomycosis, mostly due to pharmacokinetics of medication penetration in nails and skin. A six week course of terbinafine will have a fungicidal effect for a few months. 
• Lab monitoring: There is a lack of consensus guidelines and wide variation in approach to this (Brockman & Funk, 2021). Monitoring is relatively low-yield in a pediatric population; Dr. Rohan believes it’s often reasonable to skip if using short term/pulsed therapy in a patient without complicating factors . Classically, the recommendation for adults is to monitor labs after 6 weeks of treatment with griseofulvin or terbinafine. If a pediatric patient is on an oral antifungal for several months consider checking liver function—especially if they are on any other hepatically metabolized meds. In Dr. Rohan’s opinion, if you are already ordering labs (e.g., CBC and lead monitoring), it probably makes sense to add transaminases. 

Treatment Resistance

• Consider a different diagnosis.
• Make sure patient is using medication correctly. 
• Can be sign of immunodeficiency, but this is fairly rare.

Goal

Listeners will explain the basic diagnosis, differential diagnosis, and management of dermatophyte skin infections in a pediatric population, as well as recognize common disease mimickers. 

Learning Objectives

After listening to this episode listeners will…  

1. Recognize and diagnose common dermatophyte infections.
2. Identify alternative diagnoses that may mimic dermatophytes.
3. Select appropriate topical and oral medications to treat common tinea skin infections.
4. Recall risks of oral antifungal use and monitor patients appropriately for complications

Disclosures

Dr. Rohan reports no relevant financial disclosures. The Cribsiders report no relevant financial disclosures. 

Citation

Engel S, Rohan C, Cruz M, Masur S, Hane J, Berk J. “#82: Fungi Fun! An In-Depth Look at Tinea Infections”. The Cribsiders Pediatric Podcast. https:/www.thecribsiders.com/ April 12, 2023.