Hyperkeratosis lenticularis perstans is a rare skin condition that causes many small, rough, red-brown or yellow-brown bumps, most often on the lower legs and tops of the feet. It usually appears in adulthood and tends to be long lasting, though the number and look of the spots can vary over time. Not everyone will have the same experience. Hyperkeratosis lenticularis perstans is not usually dangerous or life-threatening, but some people find the bumps itchy, dry, or bothersome in daily life. Treatment focuses on symptom relief and skin care, often with moisturizers, creams that soften thick skin, and sometimes prescription creams, especially when early symptoms of Hyperkeratosis lenticularis perstans start to spread or become more noticeable.
How many people live with Hyperkeratosis lenticularis perstans?
Global and U.S. prevalence estimates for hyperkeratosis lenticularis perstans are not consistently reported by a single authoritative source. Rare-disease references describe it as exceptionally rare, but they do not provide a reliable current count for the world or for the United States.
Overview
Hyperkeratosis lenticularis perstansSymptoms
Hyperkeratosis lenticularis perstans usually causes many tiny, rough, red-brown or yellow-brown bumps, most often on the lower legs and tops of the feet. They can feel dry or scaly. Some people also notice mild itching.
Outlook and prognosis
Hyperkeratosis lenticularis perstans is usually long lasting but manageable. Many living with hyperkeratosis lenticularis perstans have stable skin spots that come and go slowly, without affecting overall health. Treatment can ease roughness and improve comfort and appearance.
Causes and risk factors
Hyperkeratosis lenticularis perstans usually stems from an inherited gene change, though the exact cause is not always clear. Family history is the main risk factor. It often appears in adulthood, and sun exposure may make spots more noticeable.
Genetic influences
Genetics can matter in Hyperkeratosis lenticularis perstans, because some families show an inherited pattern. But many cases seem to happen without a clear family history, so genetic changes are not the whole story.
Diagnosis
Diagnosis of Hyperkeratosis lenticularis perstans usually starts with a skin exam, based on the look and distribution of the rough, scaly spots. A skin biopsy may be used to confirm the diagnosis, while genetic tests are not usually needed.
Treatment and drugs
Hyperkeratosis lenticularis perstans is usually managed with regular moisturizers and creams that soften scale, such as urea or salicylic acid. Some people benefit from retinoid creams. Stubborn spots may be treated with a retinoid tablet, laser, or light freezing.
Symptoms
Many living with Hyperkeratosis lenticularis perstans first notice tiny rough spots in adulthood, often on the tops of the feet or lower legs. These marks are usually harmless but stubborn, and they can be easy to mistake for ordinary dry skin or a common rash. The early features of Hyperkeratosis lenticularis perstans are often subtle, blending into daily life until they become more noticeable. Some people have only a few spots, while others slowly develop more over time.
The most common feature is tiny, firm bumps with a dry, scaly surface. They often feel rough like sandpaper and do not smooth out easily with regular moisturizer.
The spots are often red, reddish-brown, or yellow-brown rather than skin-colored. On darker skin tones, they may look deeper brown or gray-brown and can be easier to feel than to see at first.
In Hyperkeratosis lenticularis perstans, spots usually show up on the tops of the feet and lower legs, often on both sides. Some people also notice them on the hands, thighs, or arms, while the face is less commonly affected.
New spots can appear gradually, while older ones tend to stay in place for a long time. Many people notice a slow increase over years rather than a sudden breakout.
How people usually first notice Hyperkeratosis lenticularis perstans?
People usually first notice hyperkeratosis lenticularis perstans as tiny, rough, reddish-brown or yellow-brown scaly spots that show up on the tops of the feet or lower legs and do not go away like ordinary dry skin. For many, the first signs of hyperkeratosis lenticularis perstans are patches that slowly increase in number over time, often on both sides of the body, while the skin feels sandpapery or looks dotted with small crusty bumps. Because it is uncommon and often causes few other symptoms, many living with this condition first think it is just stubborn dry skin or a rash until a dermatologist takes a closer look.
Types of Hyperkeratosis lenticularis perstans
No distinct types of Hyperkeratosis lenticularis perstans are widely recognized.
Can I slow down the onset of symptoms?
No, at this time there is no good evidence that lifestyle changes or medical treatment can meaningfully delay the start of symptoms in hyperkeratosis lenticularis perstans, a rare skin condition. Because it is uncommon and may run in families, doctors do not have proven steps such as diet changes, exercise, supplements, or early treatment that are known to reduce the risk of it starting, and research on prevention is still very limited. Gentle skin care and seeing a skin doctor can help once spots appear and can rule out similar skin problems, but they cannot promise to delay or prevent this condition.
What genetics can tell you about symptoms
Genetics may help explain why hyperkeratosis lenticularis perstans can run in some families, but they usually cannot predict exactly which spots will appear, how widespread they will be, or how bothersome they will feel. Many living with this condition have similar rough, small skin bumps, yet the number of areas involved, the age when it starts, and the overall severity can vary even within the same family. In other words, genes may influence risk and some aspects of timing or severity, but they do not give a clear, person-by-person forecast of symptoms.
Causes and risk factors
For many people with hyperkeratosis lenticularis perstans, the rough spots seem to show up without a clear everyday trigger. The exact causes of hyperkeratosis lenticularis perstans are not fully understood, but an inherited tendency seems important because it can run in families, even though some people have no family history. It usually starts in adulthood, so older age is one of the main biological risk factors. Researchers are still learning how these pieces fit together. Long-term sun exposure or repeated skin irritation may play a part in some cases, but no strong lifestyle risk factors have been clearly proven.
What are the most common causes or risk factors?
For hyperkeratosis lenticularis perstans, the exact cause is often not clear, but the best-known risk factor is family history, and in some families it appears to be passed down through genes that affect how the outer layer of the skin grows and sheds. It most often begins in adulthood, especially in middle age or later, so older age seems to raise the chance of developing it. Beyond that, no major lifestyle or environmental cause has been clearly proven.
Environmental and biological risk factors
For hyperkeratosis lenticularis perstans, the list of proven risk factors is short because the condition is rare and not fully understood. Doctors often group risks into internal (biological) and external (environmental). The clearest pattern is that it usually shows up in adulthood, while outside triggers remain uncertain. Research on what causes hyperkeratosis lenticularis perstans is still limited.
Many people with hyperkeratosis lenticularis perstans first notice skin changes in midlife or later rather than in childhood. Increasing age is the most consistent biological association reported so far.
Hyperkeratosis lenticularis perstans appears to be linked to changes in how the outer layer of skin builds up and sheds. When that process is off balance, rough, hard plugs can form more easily.
No single environmental exposure has been consistently shown to raise the risk of hyperkeratosis lenticularis perstans. Researchers have not found strong, repeatable links with common infections, everyday skin products, or routine environmental exposures.
Genetic risk factors
Many people with Hyperkeratosis lenticularis perstans want to know whether it runs in families, especially if similar rough, scaly spots have shown up in a parent or sibling. The exact genetic cause is not fully pinned down, but family patterns suggest inherited factors can play an important role in at least some cases. In other people, there is no clear family history, so the genetic causes of Hyperkeratosis lenticularis perstans are still being worked out. Risk is not destiny—it varies widely between individuals.
Family history: Having a close relative with Hyperkeratosis lenticularis perstans can raise the chance of developing it. This is one of the strongest clues that inherited factors are involved. In some families, several people across generations are affected.
Inherited pattern: In some families, Hyperkeratosis lenticularis perstans seems to follow an autosomal dominant pattern, which means the tendency can be passed on from one affected parent. Carrying a genetic change doesn’t guarantee the condition will appear. Age at onset and symptom severity can differ even within the same family.
Unclear gene: Researchers have not confirmed one single gene as the cause for most people with Hyperkeratosis lenticularis perstans. Because of that, genetic testing is not routine or clearly informative in many cases.
No known relatives: Some people with Hyperkeratosis lenticularis perstans do not know of any affected family members. This does not rule out genetics, because the condition is rare and mild symptoms in relatives can be easy to miss.
Lifestyle risk factors
Hyperkeratosis lenticularis perstans is a rare keratinization disorder in which lifestyle habits do not cause the condition, but they can influence how irritated, dry, or noticeable the skin becomes. In practice, how lifestyle affects Hyperkeratosis lenticularis perstans is mainly through skin barrier stress, friction, and factors that trigger inflammation. Daily habits that protect the skin may help reduce discomfort and limit secondary problems such as cracking or infection.
Long hot showers, harsh soaps, and frequent washing can strip skin oils and make the rough papules drier and more prominent. Regular use of gentle cleansers and bland moisturizers may help soften scale and reduce fissuring.
Tight clothing, repetitive rubbing, and pressure on affected areas can aggravate scaling and make lesions feel more irritated. Reducing friction may help limit soreness, scratching, and thickening of the surface keratin.
Scratching or picking at lesions can break the skin barrier and increase the chance of bleeding, crusting, or secondary infection. Keeping nails short and treating itch early may help prevent worsening from self-trauma.
Heavy sun exposure can irritate already abnormal skin and may worsen redness or post-inflammatory pigment change in some people. Sensible sun protection can help reduce additional skin stress while protecting fragile areas.
Risk prevention
For people living with Hyperkeratosis lenticularis perstans, there is no proven way to prevent the condition itself because it is thought to be linked to inherited skin changes. Prevention usually means lowering the chance of irritation, dryness, infection, and worsening spots over time. Prevention is flexible—it adapts to your life and health background.
Regular use of a thick, fragrance-free moisturizer can soften rough skin and reduce cracking. This may help lower irritation in Hyperkeratosis lenticularis perstans, especially after bathing or during cold, dry weather.
Mild cleansers and lukewarm water are often better than hot showers, harsh soaps, or rough scrubbing. If you are wondering how to prevent skin irritation in Hyperkeratosis lenticularis perstans, gentle daily skin care is one of the most practical steps.
Friction from tight clothing, repeated scratching, or aggressive exfoliation can make affected areas more uncomfortable. Many with Hyperkeratosis lenticularis perstans do better when they protect the skin and avoid picking at raised spots.
When skin starts to feel tight, flaky, or sore, stepping up moisturizing and reducing irritants can help prevent small cracks. This matters because broken skin can sting and may raise the risk of infection.
Can you prevent Hyperkeratosis lenticularis perstans?
No, there is no known way to fully prevent hyperkeratosis lenticularis perstans. It often seems to be linked to genes and may run in families, so many living with it could not have stopped it from happening. Gentle skin care, such as avoiding harsh products and reducing skin irritation, may help with comfort, but this has not been proven to prevent the condition.
Transmission
Hyperkeratosis lenticularis perstans is not contagious, so it does not spread through touch, shared items, close contact, or the air. If several people in one family have it, that reflects inheritance rather than infection.
When Hyperkeratosis lenticularis perstans runs in families, a parent with the condition may pass on the tendency to a child, although many living with Hyperkeratosis lenticularis perstans have no clear family history. Because of that, how Hyperkeratosis lenticularis perstans is inherited is not fully settled, but its infectiousness is not a concern.
When to test your genes
For hyperkeratosis lenticularis perstans, genetic testing is not routine because diagnosis is usually made from the skin exam and sometimes a biopsy. Consider genetic counseling or testing if several relatives are affected or lesions appear unusually early, mainly to clarify an inherited pattern and guide family planning, not to change treatment.
Diagnosis
Hyperkeratosis lenticularis perstans is usually diagnosed by combining the look of the skin spots with a close skin exam and, when needed, a small skin sample. Many living with Hyperkeratosis lenticularis perstans notice tiny rough red-brown bumps on the lower legs or tops of the feet that linger for years, which often prompts an evaluation. Doctors usually begin by looking at where the spots appear, how they feel, and whether they have changed over time. The diagnosis of Hyperkeratosis lenticularis perstans often becomes clearer once other causes of scaly or crusted spots are ruled out.
A clinician checks the size, color, scale, and distribution of the spots, especially on the lower legs and feet. In Hyperkeratosis lenticularis perstans, the bumps are often small, rough, and persistent rather than coming and going.
Your doctor asks when the spots first appeared, whether they itch or bleed, and if anything seems to make them better or worse. A detailed family and health history can help because some cases appear to run in families.
A handheld magnifying light may be used to look more closely at the surface pattern of the lesions. This can help your doctor decide whether the spots fit Hyperkeratosis lenticularis perstans or look more like another skin condition.
If the diagnosis is uncertain, a small piece of skin may be removed after numbing the area and examined under a microscope. This is often the most helpful test for confirming Hyperkeratosis lenticularis perstans because it shows the typical pattern of thickened outer skin and inflammation.
How is Hyperkeratosis lenticularis perstans diagnosed?
Hyperkeratosis lenticularis perstans is usually diagnosed by a skin doctor after looking closely at the spots and asking when they started, whether they have changed, and whether others in the family have had similar skin changes. The diagnosis is often based on the typical pattern of many small, rough, reddish-brown or yellow-brown scaly spots, most often on the lower legs and feet, and if the diagnosis is not clear, the doctor may take a tiny skin sample to examine under a microscope. Genetic testing is not usually needed in everyday care.
Stages of Hyperkeratosis lenticularis perstans
Hyperkeratosis lenticularis perstans does not have defined progression stages. This is because it usually appears as long-lasting rough, scaly spots rather than moving through clear step-by-step phases over time. Doctors usually start with a conversation about when the spots first appeared, whether they itch or feel tender, and whether the early symptoms of Hyperkeratosis lenticularis perstans have changed slowly over the years. Diagnosis is usually based on the skin’s appearance, and in some cases a small skin sample may be checked under a microscope to confirm it and rule out other skin conditions.
Outlook and prognosis
Hyperkeratosis lenticularis perstans usually has an excellent overall prognosis because it is a chronic but benign skin disorder that does not affect life expectancy or internal organs. The lesions often persist for years and may slowly increase in number with age, but they typically remain limited to the skin and are most often a cosmetic concern. Symptoms such as mild itching can occur, yet severe complications are uncommon. Treatment can improve the appearance or discomfort in some people, although responses are often partial and relapses after stopping therapy are common. There is no known increase in mortality associated with hyperkeratosis lenticularis perstans.
Long-term effects
For many living with hyperkeratosis lenticularis perstans, the main long-term effect is a lasting pattern of small, rough skin spots that tend to come and go very slowly, if at all. The condition is usually limited to the skin and does not affect life expectancy, but its visible nature can still wear on confidence over time. It’s important to remember that long-term doesn’t always mean progressive, because many people have stable areas for years.
Hyperkeratosis lenticularis perstans often causes small, rough, reddish-brown or yellow-brown spots that can remain for many years. These areas are most often seen on the lower legs and tops of the feet and may stay in the same general pattern over time.
In some people, the number of spots gradually increases over the years rather than changing quickly. The long-term effects of hyperkeratosis lenticularis perstans can include spread to nearby areas such as the thighs, hands, or arms, although this varies widely.
The affected skin often keeps a dry, sandpapery feel because of extra buildup in the outer layer. Many people notice small adjustments—like sleeves or socks catching more easily on the rough patches.
The spots can stay darker, redder, or more noticeable than the surrounding skin for a long time. Even when the surface scale loosens, the color difference may remain and keep the skin looking uneven.
How is it to live with Hyperkeratosis lenticularis perstans?
Living with hyperkeratosis lenticularis perstans often means dealing with many tiny, rough, reddish-brown scaly spots, most often on the lower legs and feet, that can be persistent and frustrating because they are visible and may make some people feel self-conscious. For many living with this condition, day-to-day life is affected more by skin care routines, cosmetic concerns, and occasional itching or irritation than by serious physical limitations, although symptoms can vary from person to person. It is not contagious, so it does not pose a risk to family, friends, or coworkers, but the emotional impact can still ripple outward when loved ones see the stress, embarrassment, or uncertainty that a long-lasting skin condition can bring.
Treatment and drugs
Hyperkeratosis lenticularis perstans is a long-term skin condition, so treatment usually aims to soften the rough, scaly spots and make them less noticeable rather than cure the condition completely. Creams and ointments that moisturize the skin or gently loosen thick scale are often tried first, and some people may also be prescribed medicated creams such as retinoids, which help skin cells shed more normally. Not every treatment works the same way for every person, and because Hyperkeratosis lenticularis perstans can be stubborn, a dermatologist may suggest trying different topical treatments over time. If the spots are widespread or do not improve, some may benefit from treatments done by a skin specialist, such as light-based therapy or other procedures, though evidence is limited because this condition is rare. Alongside medical treatment, lifestyle choices play a role, including gentle skin care, regular moisturizing, and avoiding picking or harsh scrubbing, which can further irritate the skin.
Can you cure Hyperkeratosis lenticularis perstans?
No, there is no cure for hyperkeratosis lenticularis perstans right now. Treatment can often soften the rough spots, ease itching or irritation, and improve how the skin looks, usually with moisturizers and medicated creams, and sometimes with light or laser treatment. Even with treatment, the spots may come back, so ongoing skin care is often needed.
Non-drug treatment
Living with Hyperkeratosis lenticularis perstans can mean rough, scaly spots on the lower legs or feet that are more noticeable than painful, but they may still feel bothersome day to day. Non-drug care focuses on softening thick skin, reducing irritation, and helping people feel more comfortable in their skin. Managing this condition often starts with gentle skin care habits at home and, for some, office-based skin procedures. Not every approach works the same way, so treatment is usually tailored to how widespread the spots are and how much they bother you.
Thick, fragrance-free creams or ointments can help soften dry, rough patches and support the skin barrier. Applying them after bathing often works best because they help lock in moisture.
Brief soaks in lukewarm water can loosen surface scale and make the skin feel less tight. Hot water and long baths may dry the skin further, so gentle routines are usually better.
Careful use of a soft washcloth or other gentle exfoliation can help lift loose scale without scraping the skin. Rubbing too hard may worsen redness or irritation, especially if the spots are already sensitive.
Many people with Hyperkeratosis lenticularis perstans do better with mild cleansers, loose clothing, and avoiding friction from tight socks or shoes. These steps will not remove the spots, but they can help prevent extra dryness and discomfort.
Your genes may have an impact on how drugs work for you
For people living with hyperkeratosis lenticularis perstans, treatment usually focuses on skin care, such as thick moisturizers and creams that help soften and shed rough skin, and there is no well-established evidence that inherited gene differences clearly change how these treatments work. Some may find that one cream helps more than another, or that stronger treatments like vitamin A-related medicines irritate the skin, but this is usually judged by how the skin responds over time rather than by genetic testing. In short, genes may play a role in the condition itself, but they are not currently used in a routine, proven way to guide medication choices for this condition.
Pharmacological treatments
For many living with Hyperkeratosis lenticularis perstans, treatment is mainly about softening rough spots, reducing scale, and making the skin feel more comfortable rather than curing the condition. Because this rare skin disorder can be stubborn, medicines often help only partly and may need regular use to keep areas from thickening again. Not everyone responds to the same medication in the same way. If you are looking into treatment for Hyperkeratosis lenticularis perstans, the medicines used are usually creams, ointments, or, in more widespread cases, tablets.
Creams with salicylic acid or urea are often used first to loosen and thin the built-up outer skin layer. They can help rough bumps feel smoother, especially on the lower legs and tops of the feet. Mild stinging or irritation can happen, particularly on sensitive skin.
Tretinoin or tazarotene may help normalize how quickly skin cells build up and shed. Some people notice flatter, less rough spots after steady use, although redness and peeling are common at first.
Calcipotriene, also called calcipotriol in some countries, is sometimes prescribed to slow abnormal skin-cell growth. It may be tried when early symptoms of Hyperkeratosis lenticularis perstans are becoming more noticeable or when simpler creams have not helped enough.
This prescription cream is occasionally used for stubborn lesions because it targets fast-growing abnormal skin cells. It can cause marked redness, soreness, and crusting while treated areas are healing.
Genetic influences
Hyperkeratosis lenticularis perstans sometimes shows up in more than one member of the same family, which suggests that genes can influence who develops it. It’s natural to ask whether family history plays a role. In some families, the pattern looks autosomal dominant, meaning a parent with the condition may pass the tendency on to a child. At the same time, many reported cases of Hyperkeratosis lenticularis perstans do not follow a clear family pattern, so genetics is probably only part of the picture. Because this condition is rare, researchers have not identified one single gene that explains all cases, and genetic testing is not usually part of routine care. If several relatives have similar rough, small spots on the legs or feet, sharing that history with a dermatologist can be helpful when early symptoms of Hyperkeratosis lenticularis perstans are being assessed.
Is Hyperkeratosis lenticularis perstans genetic?
Genetics can matter in Hyperkeratosis lenticularis perstans, because some families show an inherited pattern. But many cases seem to happen without a clear family history, so genetic changes are not the whole story.
Having a genetic risk is not necessarily a diagnosis
Changes in genes are a normal part of being human and are common across the general population. Most of these changes do not directly affect health and simply reflect natural human diversity. For many genes, carrying a change tied to a condition suggests a possible link rather than a certain diagnosis, especially when several genes and environmental factors play a role. In some situations, however, a single well-understood change in a particular gene can be enough to confirm a diagnosis.
Pharmacogenetics—how genetics influence drug effects
When the small, rough patches of hyperkeratosis lenticularis perstans do not improve much with creams, many living with this condition wonder whether genes also affect treatment. Genes may help explain why hyperkeratosis lenticularis perstans can run in some families, but the exact genetic cause is still unclear in many people. At this point, there is no well-established pharmacogenetic test that tells doctors which cream, retinoid, or other medicine will work best, so treatment options for hyperkeratosis lenticularis perstans are usually chosen based on symptoms and adjusted over time. Not every difference in response is genetic, but age, skin sensitivity, other health conditions, and how regularly treatment is used can all shape results. If a treatment is not helping, a dermatologist will usually change the strength, type, or schedule of medicine rather than rely on genetic testing alone.
Interactions with other conditions
For many living with hyperkeratosis lenticularis perstans, the main issue is usually the skin itself rather than problems in other organs. This rare condition is not usually known to directly cause other diseases, and most people do not develop broader health problems because of hyperkeratosis lenticularis perstans alone. Still, its rough, reddish-brown, scaly spots can resemble other skin conditions such as eczema, psoriasis, or sun-related skin changes, which can make diagnosis less straightforward. Having more than one diagnosis can make symptoms feel harder to untangle, especially if itching, dryness, or irritation are coming from more than one skin problem at the same time. Interactions can look very different from person to person. If new lesions appear, change quickly, bleed, or do not heal, it is important to have them checked so a clinician can rule out another skin disease rather than assuming it is only hyperkeratosis lenticularis perstans.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
What other conditions can cause similar symptoms to Hyperkeratosis lenticularis perstans?
Several skin problems can look a lot like hyperkeratosis lenticularis perstans, especially psoriasis, eczema, small wart-like growths, and rough sun-damaged spots called actinic keratoses. Doctors may also consider other causes of tiny, scaly bumps on the legs or feet, including porokeratosis, which is another skin condition that can make round, rough patches. Because these spots can look very similar, a skin specialist may need to examine them closely, and sometimes test a small skin sample, to tell them apart.
History
People living with this condition often first notice many tiny, rough bumps on the tops of the feet or lower legs that seem to linger for years. Hyperkeratosis lenticularis perstans, sometimes called Flegel disease, entered the medical literature in the mid-20th century, when doctors began describing this distinctive pattern of small, reddish-brown, scaly spots that tended to affect adults.
At first, doctors understood it mainly through what they could see on the skin and through microscope findings after a skin sample was examined. In recent decades, awareness has grown, and Hyperkeratosis lenticularis perstans has been recognized more clearly as a long-term disorder of skin thickening rather than just an unusual rash. That mattered because the spots can look like several other skin conditions, so earlier reports sometimes grouped different problems together.
As medical science evolved, doctors learned that Hyperkeratosis lenticularis perstans can run in some families, which pointed researchers toward a genetic basis, although the exact biology was worked out much later. Even so, much of its history has been shaped by how uncommon it is: many clinicians may never see a case, and some people spend years being told their rough spots are simply dry skin or age-related changes. Knowing the condition’s history helps explain why diagnosis can still be delayed and why careful skin examination remains so important when the early symptoms of Hyperkeratosis lenticularis perstans appear.