Toenail fungus, medically known as onychomycosis, is a prevalent nail infection. While changes in nail appearance like discoloration, thickening, or brittleness often suggest its presence, accurately identifying the cause frequently requires a closer look. Healthcare professionals often use microscopic examination to confirm a fungal infection.
Preparing for the Microscopic View
Before a sample can be examined under a microscope, it must be carefully collected from the affected nail. This typically involves a healthcare provider scraping nail debris from underneath the nail plate or clipping a small piece of the nail, often from the most affected area.
Once collected, the sample undergoes a preparation process involving a potassium hydroxide (KOH) solution. A drop of KOH is added to the nail specimen on a glass slide. This solution dissolves keratin, the main protein in nails and skin cells, leaving fungal structures intact.
The slide may then be gently heated to speed up the dissolution process. This preparation clears away obscuring nail and skin cells, making fungal elements easier to see. Stains, such as Calcofluor White or India ink, can also enhance visibility.
What Appears Under the Lens
Under the microscope, fungal elements present distinct appearances that help in diagnosis. Dermatophytes, the most common cause of toenail fungus, appear as long, branching, thread-like structures called hyphae. These hyphae often have internal divisions, known as septa, appearing as cross-walls, giving them a segmented look.
Septate hyphae may display various branching patterns, sometimes appearing somewhat irregular or tangled. Their presence is a strong indicator of a dermatophyte infection. The overall morphology, including their width and the consistency of their walls, provides further clues.
Fungal spores, which are reproductive structures, can also be seen. These usually appear as oval, round, or sometimes irregularly shaped bodies. While their presence confirms fungal activity, their specific shape and arrangement can vary depending on the fungal species.
In cases of yeast infections, such as those caused by Candida species, different structures are visible. Instead of true hyphae, one might observe pseudohyphae, which are elongated yeast cells that remain attached to each other after budding, forming chain-like structures with constrictions at the points of attachment, resembling a string of sausages. Additionally, budding yeast cells are characteristic, appearing as individual oval or round cells with smaller “buds” detaching or still attached to the parent cell. Identifying these specific features helps differentiate between dermatophytes and yeasts or molds as the cause.
Why Microscopic Identification Matters
Microscopic examination is important for confirming toenail fungal infections. Many non-fungal conditions, such as psoriasis, nail trauma, or bacterial infections, can cause similar nail changes, leading to potential misdiagnosis. A microscopic view provides direct evidence of fungal presence, offering definitive confirmation.
This direct observation aids differential diagnosis, helping healthcare providers distinguish between a true fungal infection and other nail disorders. Without this confirmation, a patient might receive inappropriate treatment for a non-fungal condition, which would not resolve the problem and could lead to unnecessary medication or procedures.
While microscopy may not identify the exact species of fungus, it can often differentiate between major groups like dermatophytes and yeasts. This general classification can influence initial treatment choices, as different types of fungi may respond differently to certain antifungal medications.
Limitations and Further Diagnostic Steps
Despite its utility, microscopic examination alone has limitations. While it can confirm fungal elements and often distinguish between general types like dermatophytes and yeasts, it usually cannot identify the specific fungal species. This detailed identification often requires further testing, as different species may respond optimally to specific antifungal treatments.
False-negative results are possible, where a fungal infection is present but not detected under the microscope. This can occur if fungal elements are sparse in the collected sample, or if sample collection was inadequate. Thick and coarse nail debris can also make it difficult to visualize sparse hyphae.
For a more complete diagnosis, especially when microscopic results are inconclusive or precise species identification is needed, other diagnostic methods are often employed. Fungal culture involves growing the collected nail sample in a laboratory to identify the specific fungal species. Polymerase Chain Reaction (PCR) testing offers a faster, more sensitive method for identifying fungal DNA, allowing for quicker, more precise species identification.