Pediatric Tinea Versicolor Workup
- Author: Lyubomir A Dourmishev, MD, PhD; Chief Editor: Dirk M Elston, MD more...
The diagnosis of tinea versicolor is usually made based on clinical examination findings; however, the diagnosis is easily confirmed with microscopic examination of scales soaked in 10-15% potassium hydroxide (KOH). See the images below.
Microscopic examination demonstrates the characteristic thick-walled spherical or oval yeast forms and coarse septate mycelium, often broken up into short filaments. This combination of mycelium strands and numerous spores is commonly referred to as "spaghetti and meatballs."
Liquid blue ink, methylene blue, or Swartz-Medrik stain can be added to the KOH preparation for better visualization of the causative organism.
Scales may also be removed using clear adhesive tape; they are then directly examined. The tape must be clear and is pressed several times over involved areas of skin. The tape is then lightly pressed, sticky side down, onto a microscope slide. A small drop of methylene blue or other appropriate stain is placed at the edge of the tape and allowed to run between the tape and the glass slide. Spores, often in grapelike clumps, and mycelium are easily seen. See the image below.
A few reports in literature have recently stated that 1% Chicago Sky Blue 6B (CSB) staining with 10% KOH is a new promising contrast diagnostic method for pityriasis versicolor, with 100% of sensitivity compared with 60.9% in culture.
M furfur is a dimorphic lipophilic organism, which is cultured only in media enriched with C12-sized to C14-sized fatty acids. It is not a dermatophyte, does not grow on DTM, and does not respond to griseofulvin therapy.
If inoculated into lipid-rich media, the scales of tinea versicolor show spherical yeasts that produce the mycelial phase of the normal flora yeast P orbiculare. Scales that show mycelium and clusters of oval yeasts on direct microscopy grow P ovale on culture.
Colonization by M furfur is especially dense in the scalp, the upper trunk, and the flexures. In patients with clinical disease, the organism occurs in both the filamentous (hyphal) and the yeast (spore) stage forms.
The disease does not require any imaging studies.
Wood lamp evaluation
Pityriasis versicolor showe blue-green fluorescence of macular dyschromic lesions if irradiated by ultraviolet light with wavelength of approximately 365 nm (black light). However, the test findings may be negative in individuals on antimycotic therapy of those who have recently showered because the fluorescent is water soluble.
The characteristic histological changes include hyperkeratosis, parakeratosis, and slight acanthosis with a mild perivascular inflammatory infiltrate in the upper dermis. The organism is usually present in the upper layers of the stratum corneum, and electron microscopy reveals invasion between and within the keratinized cells.
M furfur is detected by hematoxylin and eosin (H and E) stain alone, although periodic acid-Schiff (PAS) or methenamine-silver staining facilitates detection.
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