Wednesday, October 14

Diagnosis of tinea (pityriasis) versicolor fungal infections

Malassezia furfur > Tinea versicolor > Causes > Symptoms > Diagnosis > Treatment

Diagnosis of tinea versicolor can be easily done with visual examination and when in doubt can be confirmed by Wood's lamp or by KOH test.

Diagnosis of tinea versicolor by visual observations

An experienced dermatologist can easily do the diagnosis of the presence of tinea versicolor by visual observations. The area of infection, age of the person involved, climatic condition, and the history of earlier infections can guide him to the exact problem. The flat, round or oval lesions with thin dusty scales, growing and merging to form large patches shows the presence of tinea versicolor.

Diagnosis of tinea versicolor by Wood's lamp

Wood's lamp generates UV light and is fitted with Wood's filter alowing only rays of bandwith around 365 nm.to pass through. Though the use of Wood's lamp does not require particular skill attention must be given to following aspects to get correct results and diagnosis. The lamp must be allowed to warm up for one minute.

The examination must be carried out in a dark room. Alternatively a lamp with a hood to cover the area under examination with a peephole to see the affected area can be used. The lamp must be held about 4 - 6 inches from the skin lesion under diagnosis. Washing the affected area before the examination may mislead the diagnosis and should be avoided.

Topical applications on the skin should be wiped off as these may give their own fluorescence and mislead the results. Looking directly at the UV light should be avoided. There is very scant fluorescence from the normal skin whereas Malassezia furfur emits copper orange or yellowish white light. This examination can detect even subclinical tinea versicolor fungal infection and also show the extent of the fungal infection.

Diagnosis of tinea versicolor by KOH test

Alternatively skin scraping may be viewed under microscope to detect the presence of fungus. The superficial skin sample is taken by scraping the affected skin with a scalpel or blade. The collected sample is placed on a slide. The scrapping must be taken from the margin of the lesion.

About 3 drops of 10% KOH (potassium hydroxide) solution is added to the slide. The slide is warmed to dissolve the skin tissue. A drop of lactophenol blue is added and coverslip placed. The sample is examined with a light microscope at high magnification.
tinea versicolor infections
Tinea versicolor infection
spaghetti and meatballs appearance of tinea versicolor under microscope
Spaghetti and meatballs appearance of tinea versicolor under microscope

The KOH dissolves the skin tissue leaving behind the fungal cells. The fungal hyphae can be clearly seen. Malassezia furfur can be seen showing the spaghetti and meatballs appearance. Once the diagnosis is completed and the presence of tinea versicolor fungal infection is established the disease can be treated and resolved.


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