Steve McClain, MD

Maceration, one form of bullous tinea, begins with a white plaque, with separation or lysis occurring beneath an upper cornified layer. Fungi proliferate in layers just above squamous epidermis. Shearing forces readily detach the upper sheet of infected cornified cells, which may be peeled off intact, leaving a defined edge at the base, more felt than seen in interdigital tinea after the foot has been vigorously washed.

Maceration occurs in established tinea having a thick cornified layer. With addition of water, fungal growth accelerates, repeatedly blooming, growing layer upon layer of PAS+ liquid dotted by innumerable amoeboid and granular immature fungal forms stained by PAS and Alcian Blue, in addition to PAS+ hyphae throughout. Repeated blooming gives rise to multiple fungal layers and planes of separation.

8x4mm Sheet of cornified cells with hyphae and tiny fungal colonies as viewed in the laboratory after formalin fixation

CONFIRMING THE DIAGNOSIS: Using a plain 10x lens, the astute clinician observes yellow hyphae and other fungal structures coursing through the cornified sheet, clinching the diagnosis, as in this biopsy photograph above. Those with a microscope can examine directly by adding a drop of caustic, 10% KOH, to hydrolyze the cornified sheet placed on a glass slide, and direct KOH slide examination is billable as CPT 87220. For most podiatrists, a sample in formalin to pathology or a culture is confirmatory, yet a good many others proceed to treat with topical antifungals without confirmation. Those podiatrists I suspect are experienced and certainly have experienced that false negative lab results are common.

FAIR WARNING: Fungi are difficult to see or grow, even where clinically obvious, and labs do not perform stains equally. Podiatrists must not be swayed by false-negative lab results, meaning treatment should continue where clinical improvement is apparent. KEEP TREATING. In other words, where clinical diagnosis and response to treatment indicate fungal infection, a negative lab test can be safely judged to be a false-negative and ignored.

The good news from the laboratory is that greatly improved fungal detection is accomplished by adding Alcian Blue to the PAS stain. PAS or Periodic Acid Schiff biochemically stains fungal carbohydrates red, while Alcian Blue avidly stains fungal mucins blue. In our laboratory, two stains are far better than one, revealing a panorama of red fungal carbohydrate and blue fungal mucin with purple staining where both co-localize. In the second image below, the fungal layers preferentially stain with Alcian Blue, with a few PAS+ hyphae, yet the diagnosis is obvious by either stain. In onychomycosis, adding Alcian Blue to PAS improves fungal detection significantly, by 25% or more.

Some Podiatrists prefer Fungal Cultures, yet 2-5 cultures may be necessary to grow and therefore detect pathogenic fungus, due to inherent low sensitivity and rapid overgrowth of bacteria and molds. Again, Podiatrists must be prepared to ignore negative lab results. Histopathologic study is several-times more sensitive than one culture in routine practice. One superficial biopsy is generally sufficient for histopathologic diagnosis in macerated tinea. In a few cases with persistent infections, deeper biopsy by shave biopsy or punch biopsy may be necessary.

By definition, maceration is complicated tinea, prone to ulceration and secondary bacterial infection. Maceration around a diabetic ulcer is frequent. In my opinion, presence of maceration around a diabetic foot ulcer not only indicates an excess of moisture, but more importantly, is an unequivocal sign of fungal infection in that foot ulcer, a diagnosis readily confirmed first by counting the obvious fungal nails on that foot and second by pathologic study of the ulcer debridement. [NOTE: The reader is warned my opinion goes beyond the norm of present medical thinking, which holds these wounds to be uninfected. Some podiatrists and wound experts may be inclined to regard the statement as heresy, yet by my own observations, it is true nonetheless. However, this fungal ulcer notion is too complicated a story for present discussion and will be taken up at a future date.]

The next installment will review Gentian Violet, an old but still effective antiseptic treatment for macerated tinea and also, in some podiatrist's hands, diabetic foot ulcer.

Hyphae among cornified cells staining by PAS, but negative for Alcian Blue

Fungal Callous- Blue mucinous layers of immature fungi stained by Alcian Blue, dotted by PAS+ hyphae

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References

Steedman, RF. Alcian Blue 8GS: A New Stain for Mucin. Microsc. Sci., v. 91, 477-479. 1950. Download a copy of this classic single author paper from http://jcs.biologists.org/content/s3-91/16/477.full.pdf

Notes: Case referred by Dr. Myron Boxer, DPM for pathologic study. All stains were studied using photomicroscopes at McClain Laboratories, LLC

McClain Laboratories, LLC is an anatomic pathology laboratory located in Smithtown, New York. We specialize in evaluation of tissue biopsies, with an expertise in skin, nail, and oral pathology for healthcare professionals nationwide. Gross and microscopic evaluations of specimens done at our laboratory feature: Color images on all reports Personalized imaging for research Review of prior biopsies Rapid turnaround time Specimen courier service Histology grant and research work Expert medical testimony

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