Poliosis circumscripta is a localized patch of white or gray hair caused by reduced or absent melanin in the affected hair follicles. It can appear on the scalp, eyebrows, eyelashes, or any other hair-bearing skin, and it shows up at any age. The white forelock above the forehead is perhaps the most recognizable version, but poliosis is not one disease so much as a visible sign that something has disrupted the pigment-producing cells in a specific cluster of hair follicles. That “something” ranges from inherited genetic conditions to autoimmune disorders to certain cancer treatments, and figuring out which cause is at work matters more than the white patch itself.
What Happens Inside the Hair Follicle
Hair color comes from melanocytes, the cells that produce melanin pigment and transfer it into growing hair fibers. In poliosis, those melanocytes are either missing entirely from the hair bulb or still present but no longer producing melanin effectively. Under a microscope, affected follicles show decreased or absent melanin and melanocytes in the hair bulbs compared with normally pigmented follicles nearby.1PubMed. Poliosis circumscripta: overview and underlying causes This is different from ordinary age-related graying, where melanocyte stem cells gradually deplete across most of the scalp over years. In poliosis, the loss is sharply defined: one patch loses color while surrounding hair stays normal.
The distinction matters because the underlying mechanism determines whether the white hair is permanent or potentially reversible. When the melanocytes have been destroyed outright, as happens in some genetic conditions, repigmentation is unlikely without intervention. When they have been temporarily suppressed or displaced by inflammation, the hair sometimes regains color once the trigger resolves.
Genetic Conditions That Cause a White Forelock From Birth
A white forelock present from birth or early childhood is often the first clue to an inherited condition affecting melanocyte development. Two of the best-studied examples are piebaldism and Waardenburg syndrome, and they involve different genes with different downstream consequences.
Piebaldism
Piebaldism results from mutations in the KIT gene, which encodes a receptor that melanocyte precursor cells need in order to migrate, survive, and function during embryonic development. When KIT signaling is disrupted, certain skin regions end up with few or no melanocytes, producing patches of white skin and white hair that are typically stable throughout life. The white forelock is the hallmark feature, though depigmented patches on the chest, abdomen, and limbs are common too.
KIT mutations vary in severity depending on which part of the protein they affect. Mutations hitting the intracellular tyrosine kinase domain tend to produce more extensive depigmentation than mutations elsewhere in the gene. One well-documented family carried a novel Val620Ala mutation in the KIT tyrosine kinase domain and showed progressive depigmentation over time, which is unusual for piebaldism and was not seen in family members without the mutation or in dozens of unrelated controls.2PubMed. A novel KIT mutation results in piebaldism with progressive depigmentation Most cases of piebaldism remain stable, but this progressive variant illustrates how different mutations in the same gene can produce different clinical pictures.
Waardenburg Syndrome
Waardenburg syndrome is a group of inherited conditions that pair pigment abnormalities with hearing loss and sometimes structural facial features. The white forelock and differently colored irises get the most attention, but the hearing loss is usually the most medically significant feature. There are multiple types, each with a distinct pattern of findings. Type I is characterized by a wide nasal root, short philtrum, and a specific displacement of the inner corners of the eyes called dystopia canthorum. Type II involves sensorineural deafness and iris color differences but without the displaced eye corners. Type III, also known as Klein-Waardenburg syndrome, adds musculoskeletal abnormalities including underdeveloped arm muscles, fused fingers, and missing ribs.3PubMed Central. Waardenburg Syndrome: A Report of a Rare Case
The practical takeaway is that a child born with a white forelock should be evaluated for hearing function, regardless of whether Waardenburg syndrome is formally suspected. Early identification of hearing loss makes a meaningful difference for speech and language development, and the white forelock may be the most visible early sign that prompts that evaluation.
Autoimmune and Inflammatory Causes
When poliosis appears later in life rather than at birth, autoimmune or inflammatory processes are more likely culprits. The immune system targets melanocytes in the hair follicle, either destroying them or disrupting their function enough that pigment production stops in a localized area.
Vitiligo
Vitiligo is the most common autoimmune cause of poliosis. The condition attacks melanocytes in both the skin and hair follicles, so a depigmented skin patch on the scalp often comes with white hair growing through it. When the hair turns white within a vitiligo patch, it tends to indicate that the melanocyte stem cell reservoir in the hair follicle has been depleted, which generally makes that area harder to repigment with standard treatments. White hair in vitiligo patches is considered a marker of more advanced local disease.
Vogt-Koyanagi-Harada Disease
Vogt-Koyanagi-Harada (VKH) disease is a systemic autoimmune condition that targets melanocytes throughout the body, producing eye inflammation, skin depigmentation, poliosis, and sometimes neurological symptoms. An interesting feature of VKH is that the poliosis can sometimes reverse. In a study of patients who developed poliosis and vitiligo during VKH, complete reversal of both was noted in six patients over a mean follow-up period of about 20 months. The patients whose pigmentation returned were significantly younger, averaging about 15 years old, compared with a mean age of 34 for patients whose poliosis persisted. None of the patients with reversal had a relapse of eye inflammation at 30 months, whereas nearly half of the patients without reversal did.4JAMA Network (JAMA Ophthalmology). Reversal of Poliosis and Vitiligo Following Vogt-Koyanagi-Harada Disease
This finding is genuinely intriguing: repigmentation of the hair and skin in VKH seemed to track with a better overall prognosis for the eye disease. It suggests that younger melanocyte stem cells may have a stronger capacity to recover after immune-mediated damage, and that the return of pigment might signal that the autoimmune attack has been more thoroughly controlled.
Alopecia Areata
Alopecia areata is a condition where the immune system attacks hair follicles, causing patches of hair loss. When the hair regrows, it sometimes comes back white, producing a transient form of poliosis. This white regrowth has been well documented, including in a case of a 57-year-old man whose hair regrew without pigment in areas where alopecia areata had previously caused hair loss.5PubMed. Alopecia areata with white hair regrowth: case report and review of poliosis In many cases, the hair eventually darkens over subsequent growth cycles as melanocyte function recovers, but some patients retain the white hair permanently in those patches.
Drug-Induced Poliosis
A more recently recognized cause of poliosis is cancer immunotherapy. Checkpoint inhibitors, the drugs that unleash the immune system against tumor cells, can produce autoimmune side effects affecting virtually any organ, and the melanocytes in hair follicles are no exception. This connection makes biological sense: melanoma cells share antigens with normal melanocytes, so when immunotherapy ramps up the immune response against melanoma, normal melanocytes can get caught in the crossfire.
Case reports have documented eyelash poliosis developing after treatment with the combination of ipilimumab and nivolumab for metastatic cutaneous melanoma.6PubMed. Development of Poliosis Following Checkpoint Inhibitor Treatment for Cutaneous Melanoma A larger case series at the University of Southern California reviewed melanoma patients treated between 2018 and 2023 and identified multiple patients who developed poliosis during cancer immunotherapy, including checkpoint inhibitors, bispecific antibodies, and tumor-infiltrating lymphocyte therapy.7PubMed. Development of Poliosis in Patients Treated With Immunotherapy for Metastatic Cutaneous and Non-Cutaneous Melanoma
For patients undergoing immunotherapy, the appearance of poliosis is not necessarily bad news. Skin-related side effects of checkpoint inhibitors, including vitiligo and poliosis, have been associated in some research with better tumor responses. The reasoning is that a more aggressive immune reaction against melanocyte antigens may reflect a more aggressive reaction against the tumor itself. That said, the relationship is complex, and the presence of poliosis alone is not a reliable biomarker of treatment success.
Other Triggers People May Not Expect
Not all poliosis fits neatly into the genetic or autoimmune categories. A few less common triggers are worth knowing about, particularly because they can catch people off guard.
Physical injury or localized inflammation can sometimes cause a patch of white hair. Herpes zoster (shingles) affecting the scalp has been reported to leave behind a streak of depigmented hair after the rash resolves, and radiation therapy to the head can do the same. In both cases, the inflammation or radiation damages the melanocytes in the treatment zone while leaving the hair follicle’s growth apparatus intact, so the hair continues growing but without pigment.
Halo nevi, the benign moles surrounded by a ring of depigmented skin, can produce localized poliosis when they occur near the eyelid margin. One documented case involved a man whose lower eyelid lashes turned white starting from a few central lashes and spreading over about two weeks. Examination revealed a pigmented mole roughly 4 mm across sitting just above the white lashes, with no skin depigmentation around it. The immune response directed at the mole’s melanocytes had spilled over into the nearby eyelash follicles.8PubMed Central. Poliosis of eyelashes as an unusual sign of a halo nevus
When Poliosis Shows Up in Children
Poliosis in children deserves special attention because it can be the earliest visible sign of an underlying syndrome that has not yet been fully diagnosed. A white patch of hair in an infant or young child is often what brings the family to a dermatologist, and the differential diagnosis is wide enough that a thorough evaluation is warranted. Poliosis presenting in childhood may signal genetic conditions like piebaldism, Waardenburg syndrome, or tuberous sclerosis, as well as acquired conditions that can begin early in life.9Wiley Online Library. Poliosis, hair pigment dilution, and premature graying of the hair: A diagnostic approach in pediatric patients and review of the literature Children can also present with more diffuse reductions in expected hair pigmentation, which is a related but distinct finding from the sharply localized patch seen in classic poliosis.
The diagnostic approach typically starts with a careful family history and physical exam looking for associated features: skin depigmentation, iris color differences, hearing problems, café-au-lait spots, or structural abnormalities. From there, the workup depends on the clinical picture. A child with a white forelock and hearing concerns will follow a different evaluation pathway than a child whose white patch appeared after an episode of skin inflammation.
Can the White Hair Be Reversed or Treated?
Whether poliosis can be reversed depends almost entirely on the cause. In genetic conditions like piebaldism, where the melanocytes were never there to begin with, the white hair is permanent unless treated surgically. In autoimmune conditions where melanocytes have been damaged but their stem cell reservoir is not entirely destroyed, spontaneous repigmentation sometimes occurs, as seen in the VKH patients described earlier.
For cases linked to vitiligo, topical treatments and phototherapy aimed at the surrounding skin depigmentation sometimes restore hair color too, but hair repigmentation tends to lag behind skin repigmentation and is generally harder to achieve. Hair repigmentation should be evaluated as a separate outcome from skin repigmentation because the follicular melanocyte system does not always respond in parallel with the epidermal melanocytes.10SAGE Journals (Journal of International Medical Research). Leukotrichia: A comprehensive review of follicular depigmentation
Surgical options exist for stubborn cases. Follicular unit extraction transplant has been used to restore pigmentation in focal vitiligo patches that did not respond to other treatments, including previous melanocyte-keratinocyte transplant procedures. In reported cases, transplanting pigmented follicular units into areas of refractory vitiligo and poliosis produced satisfactory repigmentation.11PubMed Central. Restoration of Pigmentation by Follicular Unit Extraction Transplant in Three Cases of Focal Vitiligo Recalcitrant to Therapy including with Previous Nonculture Melanocyte-keratinocyte Transplant This is not a first-line approach, but for people with cosmetically distressing poliosis that has failed standard therapies, it is an option worth discussing with a specialist.
Cosmetic camouflage remains the simplest route for many people. Hair dye works well on white patches of scalp hair, and tinted mascaras can cover white eyelashes. These do not address the underlying cause, but many people with isolated poliosis and no systemic condition find that cosmetic solutions are all they need or want.
The Emerging Science of Follicular Pigmentation
Research into what controls melanocyte behavior within the hair follicle is turning up some unexpected findings. One area of active investigation involves mTORC1, a signaling pathway that cells use to sense nutrients and regulate growth. Gray and white hair follicles show high mTORC1 activity, and when researchers inhibited mTORC1 with rapamycin in cultured human scalp hair follicles, the follicles not only grew more but also produced more pigment, even in gray or white follicles that still had some surviving melanocytes. The mechanism appeared to involve increased local production of a hormone called alpha-MSH, which stimulates melanin production. Conversely, when the gene for TSC2, a protein that normally keeps mTORC1 in check, was knocked down, pigmentation dropped significantly.12PubMed Central. mTORC1 activity negatively regulates human hair follicle growth and pigmentation
This line of research is still in early stages and has not led to clinical treatments for poliosis. But it hints at a future where pharmacological manipulation of follicular signaling pathways could restore pigment to white hair without surgery or transplantation. The fact that even follicles already producing gray or white hair could be coaxed back toward pigmentation, as long as some melanocytes remained, is a genuinely promising lead.
Poliosis Versus Ordinary Gray Hair
People sometimes confuse poliosis with premature graying, but the two are distinct. Premature graying, known as canities, involves a gradual, diffuse loss of melanocyte stem cells across the scalp, usually starting at the temples and progressing over years. It tends to run in families and is considered part of normal aging when it happens earlier than expected. Poliosis, by contrast, is sharply localized. You get one streak or patch of white hair while the rest stays its normal color. The abruptness and geographic specificity are the giveaways.
This distinction is clinically meaningful. Diffuse premature graying rarely signals an underlying syndrome. A well-defined white patch, especially in a child, warrants investigation. Pediatric dermatologists recognize poliosis as a potential early diagnostic clue for conditions that might otherwise go unrecognized until additional features develop.13Wiley Online Library. Poliosis, hair pigment dilution, and premature graying of the hair: A diagnostic approach in pediatric patients and review of the literature The practical message: if you or your child has a distinct patch of white hair that appeared suddenly or has been present since birth, it is worth getting checked rather than assuming it is just early graying.
Living With a White Streak
Culturally, the white forelock has been viewed in wildly different ways. In some communities it is seen as a mark of distinction or even good luck. In others, it draws unwanted attention and questions. For people who find their poliosis cosmetically distressing, the psychological impact should not be dismissed. Although it is often described as a purely cosmetic finding, the fact that it can carry diagnostic and prognostic significance means it is not something clinicians should brush off as unimportant.
For those who embrace it, the white streak requires no management at all. For those who prefer to conceal it, the options are straightforward and effective. Scalp hair responds well to standard hair dyes. Eyelash and eyebrow poliosis can be covered with semi-permanent tinting or daily cosmetic products. None of these approaches affect the underlying follicular biology, but they give people control over how visible the condition is, which for many individuals is what matters most in daily life.