Eosinophilic Folliculitis: Overview and More

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In 1965, Dr. Seiichi Ise and Dr. Shigeo Ofuji described a variant of “superficial pustular dermatosis” in a Japanese female patient with “crops of small pustules on the face, the trunk, and the upper arms without any general symptoms.” Skin exams in the patient showed pustules in the upper parts of hair follicles.

Eosinophilic folliculitis (EF), or eosinophilic pustular folliculitis (EPF), is a rare type of folliculitis (infection of the hair follicles). It causes an itchy rash and is thought to have no known causes. EF also causes itchy red bumps in and around the hair follicles. EF is sometimes called Ofuji disease after one of the doctors who first described the condition.

They would later name the skin condition eosinophilic pustular folliculitis after coming across additional cases and finding evidence of eosinophils, a type of disease-fighting white blood cell, in the hair follicles of affected people.

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There are five known types of EF. But studies looking at the number of people affected by EF are rare. Immunosuppression-associated EF is one of the more common types, affecting more males. It is commonly seen in people with HIV infections, some types of cancer, and people who have had a bone marrow transplant or a heart transplant.

In this article, we will learn about the types of EF, the symptoms and causes of the different types, and how the skin condition is treated.

Types of Eosinophilic Folliculitis

There are different variants, or types, of EF that have been described in the medical literature. The type originally described by Ise and Ofuji is the classic type.

Other types include HIV-associated eosinophilic pustular folliculitis, infantile eosinophilic pustular folliculitis, cancer-associated eosinophilic folliculitis, and medication-associated eosinophilic folliculitis. All are rare and can sometimes be mistaken for other conditions.

Classic EF

 

Classic EF appears as groups of “sterile papulopustules” on annular (ring-shaped) plaques. The term papulopustules refers to a rash consisting of papules (small raised pimples) and pustules (small filled blisters). These rashes are noninfectious (sterile). 

What Is a Papule?

A papule is a raised area of skin that is less than 1 centimeter around. Papules might have clear borders or the borders may appear broken. They appear in different shapes, sizes, and colors. When they cluster together, they form rashes. Papules are sometimes called skin lesions.

The pustules seen in classic EF are small in size and not “macroscopic” (large). Classic EF papulopustules will appear on the face, neck, and upper back. They are rarely seen on the scalp.

What Is a Pustule?

A pustule is a small bump on the skin that contains fluid or pus. Pustules will appear as white bumps surrounded by inflamed red skin. They look like pimples and can grow to be quite large. They can appear anywhere on the body and can be found in clusters.

HIV-Associated EPF

HIV-associated EPF is also called immunosuppression-associated EPF. It is common in people with advanced-stage HIV. It causes highly pruritic (itchy) urticarial (hive-like) follicular papules.

Papules are sometimes surrounded by a light-colored halo (annular plaques) in people with light skin and tend to affect the head, neck, and trunk. Annular plaques are seen in 50% of people with immunosuppression-associated EPF.

What Are Skin Plaques?

A skin plaque is an elevated, solid lesion that is wider than it is thick. Plaques are linked to many different skin conditions.

Immunosuppression-associated EPF is often misdiagnosed. Differential diagnoses (other conditions that are considered) or conditions this type of EPF might be mistaken for include acne vulgaris, rosacea, bacterial folliculitis, dermatomycosis (fungal skin infection), and seborrheic dermatitis.

Infantile EPF

Much like other types of EPF, the infantile type is extremely rare, with limited research on its occurrence and presentation. According to a 2021 report in the Journal of Cosmetic Dermatology, this rare condition appears as itchy blisters and noninfectious pustules on the skin surfaces of the scalp and face.

Infantile EPF is commonly seen in the neonatal period (the first four weeks of life). Skin biopsies and blood work in infantile EPF often show the presence of dense eosinophils, a type of disease-fighting white blood cell, found in hair follicles.

What Are Eosinophils?

Eosinophils are a type of white blood cell produced in the bone marrow. They usually make up less than 5% of the total number of white blood cells circulating in the blood.

Infantile EPF tends to affect more male babies and will cause recurrences of noninfectious pustules on the scalp. The skin condition is often not harmful and will eventually clear up on its own.

Cancer-Associated EF

Cancer type EF is a less commonly known type linked to hematologic malignancies (blood cancers), specifically leukemia and non-Hodgkin lymphoma (NHL).

Leukemia refers to different cancers of the blood cells. NHL is a type of cancer that starts in the lymphatic system. The lymphatic system is part of both your immune system and circulatory system.

Cancer type EF tends to be underrecognized and difficult to diagnose. A 2017 report in the Journal of the American Academy of Dermatology describes cancer type EF as presenting with lesions, itchy papules, and variable blisters, pustules, and urticarial lesions that appear on the head and neck, the upper trunk, and the hands. Evidence of eosinophils in hair follicles was also present.

Medication-Associated EF

Medication-associated, or drug-induced, EF can be acute (short-term) or chronic (long-term). According to a 2019 report in the Journal of Cutaneous Pathology, follicular eruptions due to the use of a particular drug are a type of hypersensitivity drug reaction.

The drug reaction shows up as pustules on the face with or without neck swelling. When drug-induced EF skin is examined, “eosinophilic infiltration” (eosinophils) might be present in the follicles and sebaceous glands.

What Are Sebaceous Glands?

The sebaceous glands are small glands in the skin that secrete oily matter called sebum into the hair follicles to lubricate skin and hair. The hair follicles are the tunnel-shaped structures of the epidermis (outer layer of the skin).

Eosinophilic Folliculitis Symptoms

General signs and symptoms of EF include itchy red dome-like papules and pustules.

Papules and pustules might look like acne or other types of folliculitis. They commonly appear on the face, neck, scalp, and trunk and can be present for weeks or even months. EF papules and pustules rarely appear on the palms and soles because there are no follicles in these areas.

Sometimes, EF lesions appear as large patches. There might be crusting if any of the lesions burst.

Once areas affected by EF are healed, the skin might appear darker than it was before EF. Those skin areas become hyperpigmented.

What Is Hyperpigmentation?

Hyperpigmentation is a term that describes skin that appears darker. It can appear in small patches over large body areas. Hyperpigmentation usually isn’t harmful but is often a sign of an underlying medical condition.

Depending on the type, people with EF may experience different symptoms than what is considered general.

  • Classic EF: This type of EF appears as noninfectious papules and pustules. The pustules are small in size. Skin involvement of classic type is often found on the face, neck, and upper back. Papules might burst and crust over.
  • Immunosuppression/HIV EF: This type of EF causes severe itchy follicular papules combined with large plaques. Immunosuppression/HIV EF type tends to cover the head, neck, and trunk.
  • Infantile EF: This type of EF appears as noninfectious pustules on the scalp of infants. These pustules might reoccur, but they often clear up spontaneously on their own. The lesions in infantile EF rarely cause crusting.
  • Cancer type EF: This type of EF can present with lesions, itchy papules, and a variety of blisters, pustules, and hive-like lesions. Cancer type EF appears on the head and neck, upper trunk, and hands.
  • Medication-associated or drug-induced EF: This type of EF appears as a drug reaction in the form of pustules on the face or other body areas. Sometimes there is neck swelling linked to this type of EF.

Psoriasis vs. Eosinophilic Folliculitis

Psoriasis is an autoimmune skin condition that causes inflammation throughout the body. That chronic inflammation leads to raised plaques and scales on the skin. These can appear anywhere on the body but mainly on the scalp, knees, elbows, and lower back.

Different types of psoriasis that might be mistaken for folliculitis are:

  • Plaque psoriasis: Symptoms of this type of psoriasis are raised, itchy, and painful skin patches called plaques.
  • Pustular psoriasis: Symptoms include pustules surrounded by inflamed or reddened skin. It may appear only on certain areas of the body, such as the hands and feet, or it may cover most of the body.
  • Guttate psoriasis: This type of psoriasis causes small scaly lesions to appear on the skin. It is the result of a bacterial infection that can resolve once the infection clears. 

Psoriasis and EF share similar features and may even coexist. Folliculitis is also sometimes linked to psoriasis. There are differences between psoriasis and EF, and it is important to distinguish between them to avoid misdiagnosis.

Most types of folliculitis are considered mild skin conditions resulting from bacteria that enter the base of the hair follicles. In addition, folliculitis only affects areas of the body where there is hair.

Psoriasis is a chronic condition that requires long-term treatment. EF can sometimes clear up on its own without any treatment. Skin involvement with EF also tends to be noninfectious, although blisters may become filled with pus. Your doctor might perform a skin biopsy if they cannot determine the source of your skin symptoms. 

Causes of Eosinophilic Folliculitis

The causes of EF are not always known, although researchers have some theories. Most believe there are immune processes in play to trigger the development of EF. They further suggest that EF might be an inflammatory condition related to immune dysregulation (the immune system malfunctioning) or an underlying infection.

Classic EF Causes

Classic EF occurs in generally healthy people and mainly affects people of a Japanese background. It is the only variety seen in people who are otherwise healthy and not immunocompromised (having an immune system that is not working at full capacity).

A 2013 review of Japanese published works aimed to examine the frequency of EF. More than 300 cases were reported. Among those, 113 cases were reported in Japan since 1980. Of those EF cases, 91 were classic type, with 73% in males and 27% in females.

No known causes of classic EF have been identified. However, researchers do believe there is some type of immune process involved.

HIV-Associated EF Causes

This type of EF is a well-known symptom in advanced HIV and in people who are immunocompromised. Inflammation of sebaceous glands and an inflammatory response that causes eosinophils and T lymphocytes might be to blame, according to a 2020 report in the journal Case Reports in Dermatology.

Skin tissue examination in HIV-associated EF has found much higher levels of CD15 (for eosinophils), CD4 (T helper), and CD7 (pan-T lymphocytes) compared with people with HIV who did not have EF.

Infantile EF Causes 

Infantile EF was first described in 1984 as a type of EF that affects babies. It is extremely rare and presents in the first few months of life. Some studies have described it as appearing as early as the first day of life to 3 years of age.

Causes of infantile EF are not yet known. However, the increased number of eosinophils found in and around lesions links the condition to some type of immunological pathology (related to an immune response).

Cancer-Associated EF Causes

People with cancer type EF often develop the condition during and after treating with chemotherapy. Much like other types of EF, people with cancer type EF have evidence of eosinophils in affected areas of skin upon a skin biopsy.

A 2017 report in the journal JAAD Case Reports looked at seven people who had EF associated with chronic lymphocytic leukemia. Of the seven patients, six were men older than 50 years. Six of the seven patients had skin biopsies that showed the presence of eosinophils.

According to the study’s authors, cancer type EF can present with other leukemias and lymphomas. It has also been reported in people with multiple myeloma, Waldenstrom macroglobulinemia, and Sézary syndrome. EF can also occur after a bone marrow or stem cell transplant.

Medication-Associated EF Causes 

Medication-associated EF is rare but is more likely to occur with the use of certain prescription drugs. It is considered a hypersensitivity drug reaction. The risk of EF is dependent on the dose and duration of treatment with a particular drug.

Some drug classes can include the risk for EF, including antibiotics, steroids and androgens, oral contraceptives, and halogens such as bromides and iodine.

Risk Factors for Folliculitis Conditions

EF is common in people who are immunocompromised, who have certain cancers, or who have a Japanese heritage, but there are no other known risk factors. Similarly, the causes for other types of folliculitis are not always known.

But many other types of folliculitis—including Staphylococcus aureus folliculitis, Malassezia folliculitis, and Pseudomonas aeruginosa folliculitis—have been linked to specific risk factors.

Risk factors for folliculitis might include:

  • Frequent shaving
  • Long-term use of antibiotics
  • A history of diabetes
  • Doing activities that cause you to sweat and those areas aren’t fully cleaned after
  • Spending time in hot tubs or saunas that haven’t been properly cleaned

Diagnosis of Eosinophilic Folliculitis

Folliculitis is generally diagnosed with a physical exam of the skin. Your doctor will go over your medical history and ask about symptoms experienced and how long those have been present. They will also want to know about medications you are on and the health conditions you have.

If symptoms are severe or your healthcare professional isn’t able to confirm a diagnosis, they might refer you to a dermatologist for additional testing. One such test might be a dermoscopy. This involves the examination of skin lesions using a handheld device called a dermatoscope. This technique is noninvasive and painless.

A skin biopsy of someone with EF will uncover eosinophils under the skin surface and around the hair follicles and sebaceous glands. Some types of EF might also show increased lymphocytes and neutrophils (different types of white blood cells) in biopsy samples.

What Is a Skin Biopsy?

A skin biopsy procedure involves cutting and removing a small sample of skin to be tested. The tissue is examined under a microscope to determine the source of skin symptoms.

In making a diagnosis, a doctor will want to distinguish EF from other types of folliculitis, including bacterial, fungal, and viral types.

Other conditions your doctor will want to rule out include different types of acne, psoriasis, rosacea, eczematous dermatitis, granuloma faciale, autoimmune annular erythema, infestations, pustular dermatosis, and cutaneous T-cell lymphomas.

Treatment for Eosinophilic Folliculitis

There are different topical and systemic treatments for EF. Your doctor will determine what might best work by considering the severity of symptoms, any preferences you might have, including convenience and cost, and how you respond to treatment.

Although some types of EF need specific treatment approaches, most can be treated with similar therapies.

Classic EF is often treated with nonsteroidal anti-inflammatory drugs (NSAIDs), including oral and topical indomethacin and naproxen. Other treatments for classic type EF include dapsone, topical and systemic steroids, isotretinoin, antibiotics, different types of phototherapy, calcineurin inhibitors such as tacrolimus ointment, and colchicine.

HIV-associated EF has been treated with antiretroviral therapy and isotretinoin therapy. HIV type does not respond well to NSAIDs.

Additional treatments for HIV type include:

Infantile EF responds well to topical corticosteroid therapy and oral antihistamines, including cetirizine. But this type of EF is benign and often resolves on its own before age 3 without any aggressive treatment.

Other types of EF are generally similar to classic EF based on the severity of symptoms. But there are no generally accepted treatment approaches.

Prognosis

EF tends to be a benign skin condition. The long-term outlook for people with EF depends on the type they have. 

Classic type is a chronic and recurrent condition but is self-limiting. Except for skin symptoms, the classic type causes no systemic (whole-body) symptoms or long-term complications. 

Infantile type is also benign and resolves in most children by the age of 3. Aggressive treatment is generally not needed and most children will remain in good health. 

Drug-associated EF tends to resolve with treatment and recurrences are uncommon.

HIV type and cancer type EF are more concerning. The overall prognosis for these two types is dependent on the underlying condition. 

Summary

Eosinophilic folliculitis is a recurrent skin condition with unknown causes. It was first discovered in 1965 and has five different types—classic, HIV/immunosuppression type, infantile, cancer type, and drug-induced.

All types of EF are self-limiting, although cancer EF and HIV EF types might be more concerning and should be treated and monitored. EF is thought to be a noninfectious eosinophilic infiltration of hair follicles, due to the presence of eosinophils, disease-fighting white blood cells. Eosinophils have been found on skin biopsies of people with EF.

Treatment is aimed at managing skin symptoms with a variety of systemic and topical therapies. The condition is not linked to any systemic symptoms or complications.

A Word From Get Meds Info

Even though most cases of eosinophilic folliculitis are harmless, it is always a good idea to reach out to your doctor anytime you experience a skin rash that doesn’t go away after a short time. In most cases, a quick exam can help your doctor to determine the source of your symptoms and provide treatment.

If you are being treated for HIV, cancer, or any condition that suppresses your immune system, or if you suspect skin symptoms are drug-induced, reach out to your doctor right away.

You should also seek medical attention if an EF rash has spread from the original areas to other body areas, affected skin areas are painful, you have bumps that are draining fluid, or you experience a fever or other systemic symptoms.

Frequently Asked Questions

  • What does eosinophilic folliculitis look like?

    EF presents as itchy red or skin-colored papules and pustules that are somewhat round-shaped. It may resemble acne or other types of folliculitis. Skin involvement in EF tends to affect the scalp, face, neck, and trunk. For some people, it presents as large hives. The palms and soles are rarely affected by EF.

  • How does eosinophilic folliculitis start? 

    Researchers aren’t sure what causes EF to start, but many speculate that faulty immune system responses might be to blame. Most types of folliculitis start when hair follicles become inflamed or infected. Early on, EF might start as small bumps on the face, neck, arms, and upper back.

    If symptoms don’t worsen, they might improve with time. However, if skin symptoms last for weeks or if bumps start to present as papules and pustules, you should reach out to your doctor or a skin specialist for diagnosis and treatment. 

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