Molluscum contagiosum is a skin infection characteristic of small benign skin-coloured spots on the skin's surface. In most individuals, this contagious viral infection causes only minor itching and no other symptoms. However, in immunocompromised individuals, there can be more severe and persistent symptoms. Knowing the differences in the way Molluscum contagiosum presents in healthy individuals as opposed to immunocompromised individuals is important for early detection and tailored medical management. 

What is molluscum contagiosum? 

Definition/Overview

Molluscum contagiosum is a contagious skin infection that causes harmless small pink or skin-coloured bumps on the skin. In normal, healthy individuals, these bumps cause no more than some mild itching but are usually painless.¹ In immunocompromised individuals, there are harsher symptoms. The spots can appear larger, vast in number, long-lasting and are usually more difficult to treat due to a reduced immune response.^2,3,4

Incidence 

Molluscum contagiosum is most common in children, due to its mode of transmission of close contact. Around 1 in 100 children per year in the UK are predicted to be affected.⁵ Immunocompromised individuals are the other group with the highest incidence of the infection, with up to 18% clinical prevalence reported in adults in the US.⁶

Transmission 

Once the virus is within the body, its incubation period is variable, from as little as 2 weeks and as long as 6 months. The molluscum virus will present as papules on the skin. These spots can rupture and release a pus-like discharge. This contains viral material which can spread to others.

It is mainly transmitted through direct skin-to-skin contact with other infected people.

Other transmission pathways include: 

• Indirect contact - shared items of clothing, towels etc
• Auto-inoculation - spread from one area of your body to another
• Sexual intercourse - by direct skin contact 

Signs and symptoms of molluscum contagiosum 

Healthy individuals

In healthy individuals, the spots have some characteristics that make them easily recognised as molluscum including;

• Small flesh/pink coloured bumps
• Usually 5mm or less in size 
• Sometimes itchy but are otherwise asymptomatic 
• “Wart-like” in appearance 
• Have a central indentation 
• Usually presents within the folds of the skin - thighs, buttocks and genitals however it can present anywhere

Immunocompromised individuals 

In immunocompromised individuals, there are harsher symptoms compared to healthy individuals. These include;

• Spots that appear larger than expected
• Increased number of spots 
• Lesions in multiple locations on the body
• Long-lasting and persistent outbreaks 
• Recurrent infection 

The bumps present more frequently in outbreaks of over 100 lesions and commonly manifest on the face of immunocompromised individuals.⁴

Complications

• Prolonged infection without spontaneous resolution 
• Secondary bacterial infections are usually caused by scratching itchy spots and breaking the skin barrier 
• Giant molluscum contagious; this is the appearance of spots that are more than 5mm  in diameter 
• Psychological and social stress may affect self-esteem and impact the quality of life for some patients with large visible spots or scarring 

Diagnosis of molluscum contagiosum 

Most clinical cases of Molluscum contagiosum can be identified by a simple medical exam in immunocompetent people. Since the presentation of molluscum in immunocompromised people can be atypical, further tests are often needed in order to rule out more serious conditions. Molluscum contagiosum can be confused with malignancies and in some cases tumours.

In rare cases, a skin biopsy can be conducted to have a closer look at the lesions under a microscope. Molluscum has characteristic viral bodies called Henderson-Patterson bodies, where the viral material is contained.⁷ These inclusion bodies confirm the diagnosis of molluscum contagiosum. However, biopsies are only done in cases where symptoms do not self-resolve and the diagnosis is inconclusive.

Often in diagnostics, the reverse can occur, where Molloscum contagiosum is a sign that something else is going on. Molluscum can be indicative of immunocompromised individuals and more specifically in HIV+ adults or children.⁸ 

Risk factors for molluscum contagiosum

HIV/AIDs

Human immunodeficiency virus (HIV) is a viral infection that attacks the CD4 (link) cells in the body. CD4 cells are a type of immune cells responsible for defending the body against infections, and therefore HIV patients often have a lower number of CD4 cells making them more susceptible to infection. Acquired immunodeficiency syndrome (AIDS) is the latter and most serious stage of this condition. There is no cure, however, with combination antiretroviral therapy treatment, many HIV+ patients can live long and healthy lives. 

The lack of immune defence in HIV+ patients results in increased susceptibility to various infections such as pneumonia, tuberculosis and skin conditions such as molluscum contagiosum.

Organ transplants 

Viral infections are very common in organ transplant patients. When patients undergo transplant surgery, they must maintain a suppressed immune system in order to stop the auto-rejection of the new organ within the body with the use of immunosuppressant medications. Although effective, it does increase the risk of infections and it may be more difficult for the body to overcome infections. For Molluscum contagiosum, there is a prevalence of approximately 7% of organ transplant recipients that obtain atypical giant Molluscum contagiosum.⁹

Immunosuppressant treatments 

Those who receive immunosuppressant treatments have similar outcomes of increased viral infections. Immunosuppressant drugs are taken for a variety of reasons, such as in cancer treatments or for autoimmune diseases such as Crohn’s disease or Rheumatoid arthritis. For example, the drug fingolimod, an immunosuppressant targeting lymphocytes, has been associated with increased severity of chickenpox, HPV and Molluscum contagiosum.¹⁰

Other high-risk groups include 

• Sexually active adults: The viral infection can be considered an STD as it is passed from skin-to-skin contact during sex 
• Individuals with eczema (or similar skin conditions): Broken and cracked skin means a compromised skin barrier which increases the chance of entrance of other bacteria/viruses leading to infection

Prevention and management of molluscum contagiosum 

Preventing an infection of Molluscum contagiosum is extremely difficult considering the infection can go unnoticed for multiple weeks and individuals can remain asymptomatic. However, once an individual has caught the infection, it is possible to prevent the spread to others.¹¹

How to avoid spreading the molluscum contagiosum virus:

• Good hygiene practices including regular hand washing and keeping the rash clean
• Covering the bumps to avoid exposure 
• Moisturising and soothing skin to reduce scratching 
• Avoiding touching or shaving over regions of outbreak as this reduces the chance of auto-inoculation 
• Keep clothes and other personal items clean and do not share them 
• Avoid sexual contact until the infection has cleared¹²

Treatment 

For most healthy individuals, the recommended treatment would be to let the infection run its course, as it will resolve itself usually over the period of a few weeks to months. Since immunocompromised individuals experience longer-lasting and distressing symptoms there are more extensive options for treatment.¹³

The primary first-line treatment in HIV+ people suffering from molluscum is antiretroviral therapy (ART). This involves a combination of different antiviral drugs to work on HIV at different stages of its lifecycle. A combination is often used to avoid any drug resistance from the virus. It has been shown that by raising the CD4 cell count, it can resolve Molluscum contagiosum in these individuals.¹⁴

Other treatment options

Summary 

Molluscum contagiosum is primarily a childhood disease that causes almost no symptoms and is completely benign. In immunocompromised individuals, however, this virus has the ability to last much longer in the body and present atypically. It is important to be able to recognise Molluscum contagiosum as it can be confused with other severe illnesses. It is also indicative of other conditions, as persistent infection can be diagnostic of immunosuppression and more specifically HIV infection. Early detection plays a vital role in preventing the virus from spreading, and it is becoming increasingly important to raise awareness about the potential severity of the virus in people with weakened immune systems. With advancing healthcare and medicine, infections are becoming more manageable in these populations, with the hope for even better management in the future.