Lichen Planus in the Nails

How does lichen planus show up in the nails?

Nail lichen planus changes the nail by attacking the nail matrix, the tissue at the base of the nail that produces new nail plate. Early signs include thinning, longitudinal ridging (fine parallel lines running the length of the nail), and a nail that splits or flakes at the free edge more easily than it should. The lunula, the pale crescent at the base of the nail, sometimes turns red or dusky.

The change that matters most is pterygium: when the matrix is damaged badly enough, the cuticle can fuse directly to the nail bed and grow forward as a wedge, permanently splitting the nail plate in two. Once a pterygium is fully formed, it does not reverse, which is the central reason nail lichen planus is treated as more urgent than lichen planus on the skin. In severe, untreated cases, an entire nail can be lost.

Multiple nails are often affected at once, sometimes all twenty in a pattern called twenty-nail dystrophy, though nail lichen planus can also involve just one or two nails and be easy to miss until the changes are well established. Nail changes can appear alone or alongside lichen planus in the genital skin, lichen planus inside the mouth, or lichen planopilaris scarring alopecia on the scalp — the same disease process turning up in different tissues.

Why does nail lichen planus get mistaken for a fungal infection?

Nail lichen planus and a fungal nail infection (onychomycosis) are the two conditions most often confused with each other, because both cause nails that look abnormal and neither hurts in early stages. The distinguishing pattern is what the nail looks like, not just that it looks bad. Fungal infection typically makes the nail thick, yellow or brown, and crumbly, usually starting at the free edge or side of one or two nails and slowly spreading. Nail lichen planus more often makes the nail thin, over-ridged, and prone to splitting, and it more commonly affects several nails at a similar stage at the same time.

Because the two need opposite treatments — an antifungal for one, an anti-inflammatory steroid for the other — confirming which one is present before treating matters. A dermatophyte (fungal) infection is confirmed with a scraping examined under the microscope or sent for culture, the standard approach clinicians use before treating suspected fungal nail disease 1Ref 1Centers for Disease Control and Prevention (2024).Clinical Overview of Ringworm.That dermatophyte infections are diagnosed with microscopy (KOH) or culture — the standard confirmatory approach used to distinguish a fungal nail infection from nail lichen planus before treating., and treatment then follows what dermatophyte infections generally require: a topical option for limited disease or an oral antifungal for more extensive infection 2Ref 2Centers for Disease Control and Prevention (2024).Treatment of Ringworm.That dermatophyte (fungal) infections are treated with topical antifungals for limited disease or oral antifungals for more extensive infection — used to describe fungal nail treatment as a contrast to nail lichen planus treatment.. Treating nail lichen planus as though it were a fungal infection wastes the narrow window when a steroid could still prevent scarring.

When do nail changes need urgent evaluation?

Most nail lichen planus is not an emergency, but a few patterns move a nail change from routine to urgent. A pigmented streak running the length of a single nail — brown or black, especially one that is new, widening, or extending onto the surrounding skin or cuticle — needs prompt evaluation, because that specific pattern is also how melanoma arising under the nail can present, and it is diagnosed and staged the same way melanoma anywhere else on the skin is 3Ref 3National Cancer Institute (PDQ Adult Treatment Editorial Board) (2025).Melanoma Treatment (PDQ®)–Health Professional Version.That melanoma arising in or under the nail is diagnosed and staged using the same approach as melanoma elsewhere on the skin — supports the safety point that a new or widening pigmented nail streak needs prompt evaluation rather than being assumed to be lichen planus..

That possibility does not describe most lichen planus nail changes, which typically involve ridging, thinning, and splitting rather than a single dark streak, and typically affect several nails rather than one. But a solitary, unusual nail — one that does not match the pattern of the others — is worth a dedicated look rather than being folded into a general nail-lichen-planus diagnosis.

How is nail lichen planus treated?

Treatment aims to calm the inflammation in the nail matrix before it scars, which makes speed more important here than almost anywhere else lichen planus appears. The same first-line steroids for lichen planus used on the skin are the starting point for nails too — a high-potency topical steroid or a steroid injected directly into the nail fold — but the nail version is escalated faster. For more aggressive disease, especially when several nails are involved or changes are progressing quickly, clinicians apply roughly the same threshold that guides severe lichen planus treatment on the skin, adding a short course of an oral or other systemic anti-inflammatory medication once local treatment alone isn't keeping pace.

Because pterygium formation is irreversible, clinicians tend to treat nail lichen planus more assertively, and sooner, than standard cutaneous lichen planus treatment on the skin — waiting to see if it resolves on its own carries a real cost that watchful waiting on the skin does not. The dose, the specific medication, and how long to continue are decisions a prescriber makes based on how many nails are affected and how quickly they are changing.

What can be expected from treatment?

Nail regrowth is slow under the best of circumstances — a fingernail takes several months to grow out fully, a toenail closer to a year — so improvement in nail lichen planus is judged gradually, by whether the new nail growing in from the matrix looks normal, not by how the already-damaged nail looks today. Treatment started before a pterygium forms has a real chance of preventing one; treatment started after a pterygium is already present can stop it from getting worse but will not undo it.

Even nails with existing damage often stabilize with treatment, and the surrounding nails have their own chance to grow in normally once the disease is controlled. For a nail that has already scarred, options are mostly cosmetic — camouflage with polish, or in some cases a specialist procedure to address the split — rather than a way to restore what the pterygium already changed.

When to see a dermatologist

Any nail changing shape, thinning, ridging, or splitting in a way that isn't explained by an injury is worth having examined, and multiple nails changing at once raises the likelihood that something systemic, like lichen planus, is behind it rather than everyday wear. Because effective treatment is time-sensitive, waiting to see whether nail changes clear up on their own is a reasonable approach for the skin but a riskier one for the nails.

Bringing a photo timeline of how a nail has changed over weeks or months helps a dermatologist judge how quickly the process is moving, which shapes how urgently to treat it. A clinician can typically tell nail lichen planus, a fungal infection, and other nail conditions apart on exam, sometimes with a nail clipping sent for testing when the picture is unclear.