Update on Molluscum Contagiosum

Molluscum contagiosum is one of the most easily spread skin diseases, making it so common that public health agencies don’t even know how many people contract it each year. In fact, the infection is very mild for the vast majority of patients; the lesions typically do not cause pain or itching and tend to heal without treatment, so finding a cure has not historically been a high priority.

But for those with a compromised immune system, molluscum contagiosum can lead to dangerous secondary infections — as well as making these individuals more susceptible to contracting secondary infections in the first place. And for HIV-positive patients, a case of molluscum contagiosum can be an indication their disease is advancing to full-blown AIDS.

Fortunately, a new, FDA-approved treatment offers physicians an effective tool to tackle molluscum contagiosum.

What Is Molluscum Contagiosum?

Although it had been described even earlier, molluscum contagiosum was named in 1817 by British doctor Thomas Bateman, MD, FLS. However, the infection was also referred to by other names until 1899, when an editorial in the Journal of the American Medical Association endorsed Dr. Bateman’s suggestion.¹

Soon after, German physician Fritz Juliusberg published a paper in 1905 explaining how he had extracted the virus he thought responsible for molluscum contagiosum from a patient’s lesions.² Later, it was discovered that a type of poxvirus — the molluscum contagiosum virus (MCV) — is responsible for the disease.

There are four subtypes of the virus, designated MCV-1 through MCV-4. MCV-1 is responsible for 98 percent of all cases and is almost always the cause of pediatric molluscum contagiosum.³ The other variant present in North America and Europe is MCV-2, which is generally responsible for sexually-transmitted cases (that primarily affect the immunocompromised).³ The other two variants are confined to Asia and Australia.

Notably, MCV is confined to the epidermis: It cannot be spread through coughing or sneezing or the exchange of bodily fluids.⁴

Pediatric MCV is most prevalent among younger children, ages 2 to 5.³ The virus can be spread through physical contact or by touching infected items such as toys, towels or playground equipment. It can also spread further on a patient’s skin through scratching or picking at the lesions.

While MCV is less common in adults, it does occur, and by the same infectious pathways. There have been recent reports that it has also spread through tattoos⁵ and eyebrow stitching.⁶

Among patients with a compromised immune system, particularly older teens and adults with HIV, transmission is the same as with healthy children but also is spread through sexual contact. It is estimated that as many as one-third of all HIV-positive patients will develop MCV at some point.⁷

For reasons that are not entirely understood, the virus seems to be more common in tropical climates.⁸

Infection with MCV does not provide immunity or protection against future infection.⁹

Symptoms and Progression

The primary symptom of molluscum contagiosum is the appearance of small, round bumps referred to as “mollusca.”¹⁰ They may be either pink in color or the same color as the surrounding skin.¹¹ The lesions are small, generally with a diameter of a quarter of an inch or less. After a few weeks, the center of the lesion will collapse, leaving a white, waxy core that gives them a distinctive appearance often described as similar to a doughnut or bagel. The lesions are generally painless. In some patients, the lesions may cause minor itchiness.¹⁰

In children, the lesions will most often appear on the arms and legs, the trunk or the face. The number of mollusca can vary widely, from one or two to large clusters containing dozens.

In most patients, there are usually no other accompanying symptoms, not even those often associated with a viral infection such as aches, fever or fatigue. (Those symptoms, if they appear in conjunction with the lesions, may be a sign of a more serious, secondary infection.¹²)

In most healthy patients, the mollusca will disappear sometime after six months to two years with no treatment.¹³

In sexually transmitted cases, MCV will manifest as lesions on the genitals, thighs or lower abdomen.¹³

Immunocompromised patients typically have far more lesions than a healthy patient, with more than 100 lesions not uncommon. The lesions can also be far larger than the typical quarter inch or smaller diameter in healthy patients — up to three-quarters of an inch or more.¹⁴ In patients with weakened immune systems, the lesions will not show any sign of healing even after several months.

In addition, the mollusca can host secondary bacterial infections, particularly in immunocompromised patients.

There have also been reports of patients reacting to the medicines used to treat molluscum contagiosum, with one child developing an autoimmune disease in response to an off-label application of imiquimod (Zyclara and Aldara).¹⁵

Another complication occurs when the lesions appear on the eyelids or other tissue near the eyes, which can lead to a form of conjunctivitis.¹⁶

Patients are contagious so long as the mollusca are visible; once the skin clears, patients are no longer shedding the virus.⁴

Diagnosis and Treatment

Due to the distinctive appearance of the lesions, diagnosis is usually made by an examination of the mollusca. If there is any doubt, a tissue sample can be sent to a laboratory for confirmation.¹⁷

For most patients, simply waiting for the body’s immune system to get rid of the MCV is the proper course of action. Young children who may spread their lesions or create scarring by scratching or scraping them may be encouraged to cover their lesions. In those cases where there is itchiness, analgesic medications may be used to relieve the symptoms. Patients with another skin condition such as eczema may require treatment to remove the lesions.

Patients with HIV or another immune disease are likely to require treatment as well. When HIV-positive patients contract MCV, it can be a sign that the disease is progressing, and further tests may be called for to determine the state of the immune system and whether the patient is developing AIDS.¹⁸ If an HIV patient presents with MCV, the physician should order tests to check the patient’s immune system.

Patients may desire immediate physical removal of the lesions, and this can be accomplished via cryotherapy (applying liquid nitrogen to freeze the cells and kill them), scraping them off or burning them off with a laser. However, the Centers for Disease Control and Prevention cautions that each of these methods will not only result in post-procedural pain and itching, but also carry the risk of permanent scarring.

Other off-label treatments that take longer to remove the lesions but don’t carry the risk of scarring include:¹⁹

• Imiquimod: a prescription topical medication that stimulates the body’s immune system (It is approved by the U.S. Food and Drug Administration [FDA] to treat genital warts and skin cancer, but has also shown promise in promoting the healing of MCV lesions.)

• Sinecatechin: a prescription topical medication developed to treat genital warts

• Salicylic acid: an over-the-counter topical treatment for warts that shows promise against MCV

• Tretinoin: an anti-acne medication applied to the lesions that provokes the body’s immune system

In severe cases in which patients with eczema also have extremely large patches of MCV lesions, and the above medications have not proven effective, the oral ulcer medication cimetidine has shown some success.¹⁸

Until just this year, treatment options were limited to these off-label drug uses,20 but FDA recently approved a new treatment specifically for MCV: YCANTH (catharidin) topical solution 0.7%.21

What Is YCANTH?

YCANTH is the first and only clinically proven treatment option formulated specifically to treat molluscum contagiosum. In summer 2023, Verrica Pharmaceuticals received FDA approval for this new treatment for adult and pediatric patients 2 years of age and older. Ycanth is administered to patients only by healthcare providers who apply a single application of the medicine on the areas of patients’ skin with molluscum bumps every three weeks as needed.

The efficacy of Ycanth was established in two double-blind, randomized, placebo-controlled trials (Trial 1 [NCT03377790] and Trial 2 [NCT03377803]). In the trials, 528 subjects ranging from ages 2 to 60 years with molluscum contagiosum were randomized by household to receive either Ycanth or a placebo treatment. Subjects received treatment or placebo at 21-day intervals until bumps were completely cleared or for a maximum of four applications. A healthcare professional who was blinded to the treatment group counted the number of lesions at each visit. The primary efficacy endpoint was the proportion of subjects achieving complete clearance of all treated molluscum bumps by day 84. Results showed 54 percent of subjects treated with Ycanth achieved complete clearance of all treated molluscum bumps by day 84 compared to 13 percent of subjects treated with placebo.

The most common adverse reactions to Ycanth occurred at the application site and included blistering, pain, itching, scabbing, reddening, discoloration, dryness, edema (swelling) and erosion of the skin. According to the researchers, life-threatening or fatal toxicities can occur if administered orally. As such, contact with the treatment area should be avoided, including oral contact, after treatment.

Prevention

There is no vaccine for molluscum contagiosum. The best prevention is to avoid physical contact or sharing clothes, bedding or toys with someone who is infected. Since most cases occur in young children, it is important that when patients are contagious their parents work to reduce the risk of transmission: by covering lesions if in a group environment and by limiting the sharing of towels or bedding in the home.

In adults, chances of contracting sexually transmitted MCV can be reduced by using a condom, but it will not eliminate the risk completely, as MCV is spread through skin contact and not bodily fluids.²¹

Continuing Research

Due to the mild nature of most cases of molluscum contagiosum, there is relatively little research into treating or curing it. In the fall of 2023, there were fewer than two dozen clinical studies listed in clinicaltrials.gov. Several of them were looking at the effectiveness of using potassium hydroxide on MCV lesions. Another, completed early in 2023, looked at the antiviral topical berdazimer,²² which shows promise against MCV. If granted final FDA approval, it could be on the market in 2024. And, while there are a handful of studies looking at further potential uses of cantharidin in treating MCV, YCANTH is a proven FDA-approved treatment for molluscum contagiosum available now.

Looking Ahead

Because of its highly contagious nature and the difficulty of devising a vaccine for a virus that resides in the outer layer of skin, physicians are likely to continue helping patients mitigate against MCV for the foreseeable future. Thankfully, the newly FDA-approved YCANTH is now a viable, available option for effectively treating it.

While most otherwise healthy patients will heal on their own, those with weakened immune systems need quick diagnosis and treatment, and YCANTH is an effective solution that meets this critical need.