Introduction

Molluscum contagiosum is a condition caused by the molluscum contagiosum virus, a poxvirus that can evade the immune system for months to years. It causes skin lesions, which tend to be harmless and self-resolve usually within 18 months. It is a contagious infection transmitted by direct skin-to-skin contact or spread through contact with a contaminated object so it is important to take necessary precautions to prevent spread by covering spots with bandages, using a condom during sex, avoiding sharing towels, bedding, or clothes, and by not scratching the spots.¹

General symptoms and signs

Appearance of Lesions 

Mollascum contagiosum lesions tend to be firm, pearly pustules. The lesions are usually natural skin tone but can also appear white. They tend to have a dome shape with an indentation in the middle, which may contain pus. The lesion sizes range from as small as a millimetre to as large as a centimetre. The amount of lesions is usually low, with the lesions typically grouping together in certain areas however in immunosuppressed individuals there can be a larger number of lesions seen.

Location of Lesions

The most common areas for lesion presence are:

• Face
• Arms
• Legs
• Abdomen
• Inner thighs
• Neck
• Genital area²

Progression of Lesions 

Initially, the pustules will form a small bump on the skin, either white or normal skin tone. These will then grow to reach their largest size and develop a head filled with pus. It is important for the patient not to pop these themselves as it could increase the risk of a secondary skin infection. Eventually, the head of pus will burst, forming a crater. This will then become a red, open sore, which should be kept clean due to the risk of secondary infection.³

Associated symptoms

As the pustules are itchy, many people may be tempted to scratch them or pick at them. This may increase the chance of developing a secondary infection, often either cellulitis or an abscess.² Cellulitis is an infection of the skin caused by bacteria, which may present with swelling, redness, painful and hot skin, and blistering. It may also cause flu-like symptoms like a fever or swelling of glands.⁴ An abscess can also form due to a bacterial infection and may be identified by the presence of a lump filled with pus, swelling, pain and redness. Both of these conditions can be treated with antibiotics if an abscess has formed, a healthcare provider may have to surgically drain it.⁵

Differential diagnoses

Similar conditions 

Warts 

A viral skin infection that may be confused with molluscum contagiosum is warts caused by the human papillomavirus (HPV). This virus causes lumps that are also flesh-coloured or white and may group together. The lesions may be either soft or firm and form around the genitals, perineum, or around the anus. They may also be accompanied by other symptoms such as painful sex difficulty urinating, and blood in the urine.⁶

Chickenpox 

Chickenpox is another disease that causes changes in the skin, caused by the varicella-zoster virus. Similarly to molluscum contagiosum, the lesions formed because of the virus undergo three stages. In the first stage, spots form that are either red, pink, or flesh-coloured. They then develop into blisters, which may burst and form a scab that can seep and appear flaky.  Chickenpox infection does not only present with lesions on the skin but also with a fever, aching of the muscles and joints, malaise, and the loss of appetite.⁷

Other skin infections 

There are multiple skin infections that may be caused by bacteria and fungi. One which may look similar to molluscum contagiosum is impetigo caused by the bacteria Staphylococcus aureus or Streptococcus pyogenes. The infection first presents with sores or blisters that are usually red in colour. These will often burst, causing scabbing.⁸ A common skin infection caused by fungi is ringworm. The name of the infection is as so due to the rash or lesion often being ring-shaped, however, the infection is not caused by worms. The rash tends to also appear red and may become dry and scaly. It can cause itchiness and pain,  and may also spread to multiple areas of the body including the scalp, groin, face, neck, and torso.⁹

Distinguishing features 

Unique characteristics of molluscum lesions 

Molluscum contagiosum may be distinguished from many other skin conditions like HPV, or chickenpox as it tends to not  not cause symptoms other than the skin lesion. With HPV warts, individuals may experience painful sex and chickenpox may cause general malaise and body aches as well as skin lesions. Also, clinical examination of the lesions by a clinician aids in the diagnosis and differentiation of the different lesions.  The lesions seen with chickenpox and impetigo burst and blister-like molluscum contagiosum however the lesion with Molluscum contagiosum will become a ‘crater’ whilst in chickenpox or impetigo the lesion usually scabs over. Ringworm is most easily identifiable with its signature ring-like rash shape hence the appearance is very different.  

Importance of clinical evaluation and diagnosis

To diagnose Molluscum contagiosum, clinicians will take a thorough history of the symptoms and perform a clinical examination, checking the appearance of the lesions. If they are unsure, they may take biopsies of the lesions, or for chickenpox or impetigo, they may take a swab of the blister and send it for culturing. The diagnosis will then dictate ongoing treatment. For impetigo, as it is caused by bacteria, antibiotics may be suggested, which would have been ineffective for molluscum contagiosum considering its caused by a virus. The same applies to the treatment of ringworm, which may include antifungals in the form of an ointment, gel, or tablets, targeting fungi specifically. For chickenpox and molluscum contagiosum treatment often is not needed as it is self-limiting, however, in serious cases both may require antivirals. For warts, the doctor may recommend topical treatment like ointments, cryotherapy (freezing the wart), or surgery to remove the warts. Similar treatments may be offered for molluscum contagiosum in certain cases.^2,6,7,8,9

Special considerations

Immunocompromised individuals 

Individuals suffering from a weakened immune system due to conditions such as Human Immunodeficiency Virus (HIV) may unfortunately experience more disseminated lesions as well as lesions that take longer than the usual 18 months to be cleared. They may also experience increased resistance to treatment, therefore altering the therapy they may require such as a tailored antiretroviral therapy regimen (treatment involving three or more antiretroviral drugs).²

Children vs. Adults 

Overall, Molluscum contagiosum is more frequently seen in children rather than adults. There is also a difference in the areas most commonly affected in adults vs children. For children, the most affected areas tend to be the trunk, face, arms, and legs and for adults, the lower abdomen, genitals, as well as inner thighs are more commonly affected.¹⁰

FAQ’s

​​Is molluscum contagiosum a STI?

Yes, molluscum contagiosum may be considered an STI as it can be transmitted through sexual contact.

How do you treat the molluscum virus?

Typically you do not need to take any treatment for molluscum virus as it will clear up on its own. In severe cases though a doctor may provide topical treatments, antivirals, or suggest cryotherapy.

Is molluscum a form of HPV?

No, they are two different viruses, which cause different diseases.

Should I pop molluscum bumps?

No, you should not pop molluscum bumps due to the risk of secondary infection. 

Summary

Molluscum contagiosum is a skin infection caused by the molluscum contagiosum virus, which causes pearly firm pustules that later burst giving a cheese-like discharge and creating crater-shaped lesions. The pustules can form anywhere on the body depending on the area of initial infection and are usually self-resolving. This, however, may take longer for immunocompromised individuals. It bears similarity to many other skin conditions caused by other viruses, bacteria, or fungi, and so accurate diagnosis is key to receiving the correct treatment.