Pediatric Dermatology Consult - July 2016

By Ellen S. Haddock, MBA, and Lawrence F. Eichenfield, MD

Molluscum

Molluscum typically presents as smooth, flesh-colored, flat-topped papules 2-8 mm in diameter with central whitish area, which is composed of the causative molluscum pox virus. While central depressions called umbilications are common, they may not be present in early molluscum lesions.^1,2 Lesions most often occur on the trunk and arms, but can occur anywhere.3-5 Individuals usually have multiple lesions, which may be clustered especially in areas of skin-to-skin contact.^5,6 Molluscum lesions can be itchy.

Molluscum is a benign viral skin infection caused by the molluscum contagiosum virus, which is a member of the poxvirus family. Molluscum infections are common, affecting 5%-11% of children.^5,7 Molluscum most often affects children younger than 8-years-old,⁵ with an average age of 5.8 years.⁸ The infection is spread through skin-to-skin contact with other individuals and by autoinoculation, which means that the infection can be spread from one area of an individual's skin to another when he or she scratches a lesion and then touches another area. It also can be spread by contact with fomites like towels and sponges.1 An association between public swimming pool use and molluscum infection has been reported, but this may have more to do with shared towels and equipment like kick-boards than transmission through the water itself.9 Molluscum sometimes is spread through contact sports like wrestling⁶ and between children sharing a bath.⁹ In adults, in whom molluscum is much less common because of acquired immunity,10 molluscum may be sexually transmitted or associated with HIV; however, this is rarely the case in children.¹

Children with atopic dermatitis have increased risk of molluscum infection in part because breaks in their skin and pruritus facilitate autoinoculation through scratching.¹¹ Not uncommonly, molluscum lesions become inflamed, with tenderness, erythema, and crust. In a study by Berger et al., 22% of patients had inflamed molluscum lesions.³ The appearance of inflamed molluscum lesions may raise concern about bacterial infection, but more often, the inflammation is a sign that the immune system is reacting to the viral infection and has almost "won the battle."¹⁰ After inflamed molluscum lesions develop, the total number of molluscum lesions typically declines,3 and some consider inflamed molluscum lesions to be a "beginning of the end sign," indicating that the infection may soon resolve.¹⁰ If the child is afebrile, lesions are itchy and painless, skin culture is negative, and there is no lymphangitis or spreading erythema, the inflammation is more likely a sign of impending resolution than bacterial secondary infection, and the urge to prescribe antibiotics should be resisted.¹⁰

As seen in this case, some patients with molluscum (5%) develop a diffuse, monomorphous, papular, or papulovesicular eruption that is an id reaction.3 This may appear to be eczema-like, lichenoid in appearance, or mimicking Gianotti-Crosti syndrome (papular acrodermatitis of childhood).³ It typically affects the arms and legs, is bilateral, and may be pruritic. The id reaction may occur in conjunction with inflamed molluscum, as is true in this case. The diffuse eruption can sometimes be mistaken for a sudden increase in the number of molluscum lesions, but the papular dermatitis lesions do not have the flat-topped dome-shape nor white centers.³ On average, the id reaction lasts about 6 weeks, after which both it and the primary molluscum lesions typically resolve.³ Although not seen in this case, more than a third of molluscum patients develop a pruritic, erythematous, eczematous area around molluscum lesions, termed molluscum dermatitis or eczema molluscatum, which may be more prominent than the molluscum itself.³ The eczematous patch typically surrounds molluscum lesions but also may occur at distant sites.¹² This reaction is especially common in patients with atopic dermatitis, 51% of whom develop it.³ It is considered a hypersensitivity reaction and may be asymptomatic or minimally pruritic.¹² Molluscum dermatitis suggests that the immune system has taken notice of the infection and is fighting it¹³; however, it does not necessarily indicate impending resolution.³

Differential diagnosis

The differential diagnosis for molluscum includes herpes simplex, warts, and milia.¹⁴ Like molluscum, herpes simplex lesions can have central umbilication, but the lesions are vesicular rather than solid. Warts typically have a rough, jagged surface in contrast to the smooth surface of molluscum lesions. Milia tend to be smaller and not flat topped. They are more common in infants and adults than in children and primarily affect the face.

Inflamed molluscum lesions and molluscum dermatitis can be mistaken for atopic dermatitis, and molluscum-associated id reactions may exacerbate atopic dermatitis. Inflamed molluscum and molluscum with id reaction could be confused with scabies, which may become crusted and also may be accompanied by id reaction. Presence of serpiginous linear burrows would suggest scabies rather than molluscum, and the diagnosis of scabies can be confirmed by scraping a burrow and looking for a mite or its feces under a microscope.

Prognosis and treatment

Molluscum infections typically resolve spontaneously in months to years (average duration, 13 months),¹⁴ so treatment may not be required. The goal of treatment is to accelerate the resolution of the infection, but some studies have found that common treatments may not shorten the time to resolution.¹¹ However, if there is substantial pruritus, lesions are cosmetically undesirable, or a child has atopic dermatitis and is at increased risk for autoinoculation, treatment may be warranted.¹⁵ Furthermore, molluscum lesions can scar, so prevention of autoinoculation may help minimize scarring.¹⁶

Few high-quality studies of the efficacy of molluscum treatments exist, and a 2009 Cochrane review found insufficient evidence to recommend any therapy for molluscum. The most common treatment used by pediatric dermatologists is cantharidin,¹⁷ and this treatment also is available to primary care practitioners. This option is preferred over other destructive methods such as curettage or liquid nitrogen cryotherapy because it is not painful or traumatic and is well tolerated by pediatric patients.⁸ Parent and physician satisfaction with the therapy is high; 78%-95% of parents would use cantharidin treatment again for molluscum recurrence.^4,8,18 Originally extracted from the blister beetle but now synthesized commercially,¹⁹ cantharidin causes vesiculation at the dermoepidermal junction6 by destroying intercellular connections.4 Vesiculation of the skin causes extrusion of the molluscum body, which facilitates resolution of the lesion.¹⁹ The cantharidin formulation is applied directly to molluscum lesions with the wooden end of a cotton-tipped applicator.⁴ Patients may be directed to wash it off after 4-6 hours. Blistering is an expected, desired outcome. A minority of patients may experience mild temporary pain (7%), more significant blistering (2.5%), burning (less than 1%), pruritus (less than 1%), or irritation (less than 1%).⁴ There is a risk of scarring and pigmentary changes, but these risks also exist for untreated lesions.¹⁹ Cantharidin treatment is repeated approximately every 4 weeks, and 90% of cases resolve after an average of 2.1 treatments.¹⁸ Topical retinoids can be used in an attempt to trigger an irritant response by the immune system, and they are the preferred therapy for facial lesions, but they are inconsistently effective.4 Randomized controlled trials found that imiquimod, a previously popular treatment is not effective,²⁰ and the evidence for cimetidine is contradictory.^21,22 Molluscum dermatitis and id reaction can be treated with medium strength topical steroids. 

References

1. Viral diseases of the skin, in "Hurwitz Clinical Pediatric Dermatology," 4 ed. (New York: Elsevier, 2011, pp. 348-69). .
2. Molluscum, in "Red Book Report of the Committee on Infectious Diseases," 2015.

Ms. Haddock is a medical student at the University of California, San Diego, and a research associate at Rady Children's Hospital-San Diego. Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children's Hospital-San Diego and professor of dermatology and pediatrics at the University of California, San Diego. Dr. Eichenfield and Ms. Haddock state they have no relevant financial disclosures.

By Ellen S. Haddock, MBA, and Lawrence F. Eichenfield, MD

Molluscum

Molluscum typically presents as smooth, flesh-colored, flat-topped papules 2-8 mm in diameter with central whitish area, which is composed of the causative molluscum pox virus. While central depressions called umbilications are common, they may not be present in early molluscum lesions.^1,2 Lesions most often occur on the trunk and arms, but can occur anywhere.3-5 Individuals usually have multiple lesions, which may be clustered especially in areas of skin-to-skin contact.^5,6 Molluscum lesions can be itchy.

Molluscum is a benign viral skin infection caused by the molluscum contagiosum virus, which is a member of the poxvirus family. Molluscum infections are common, affecting 5%-11% of children.^5,7 Molluscum most often affects children younger than 8-years-old,⁵ with an average age of 5.8 years.⁸ The infection is spread through skin-to-skin contact with other individuals and by autoinoculation, which means that the infection can be spread from one area of an individual's skin to another when he or she scratches a lesion and then touches another area. It also can be spread by contact with fomites like towels and sponges.1 An association between public swimming pool use and molluscum infection has been reported, but this may have more to do with shared towels and equipment like kick-boards than transmission through the water itself.9 Molluscum sometimes is spread through contact sports like wrestling⁶ and between children sharing a bath.⁹ In adults, in whom molluscum is much less common because of acquired immunity,10 molluscum may be sexually transmitted or associated with HIV; however, this is rarely the case in children.¹

Children with atopic dermatitis have increased risk of molluscum infection in part because breaks in their skin and pruritus facilitate autoinoculation through scratching.¹¹ Not uncommonly, molluscum lesions become inflamed, with tenderness, erythema, and crust. In a study by Berger et al., 22% of patients had inflamed molluscum lesions.³ The appearance of inflamed molluscum lesions may raise concern about bacterial infection, but more often, the inflammation is a sign that the immune system is reacting to the viral infection and has almost "won the battle."¹⁰ After inflamed molluscum lesions develop, the total number of molluscum lesions typically declines,3 and some consider inflamed molluscum lesions to be a "beginning of the end sign," indicating that the infection may soon resolve.¹⁰ If the child is afebrile, lesions are itchy and painless, skin culture is negative, and there is no lymphangitis or spreading erythema, the inflammation is more likely a sign of impending resolution than bacterial secondary infection, and the urge to prescribe antibiotics should be resisted.¹⁰

As seen in this case, some patients with molluscum (5%) develop a diffuse, monomorphous, papular, or papulovesicular eruption that is an id reaction.3 This may appear to be eczema-like, lichenoid in appearance, or mimicking Gianotti-Crosti syndrome (papular acrodermatitis of childhood).³ It typically affects the arms and legs, is bilateral, and may be pruritic. The id reaction may occur in conjunction with inflamed molluscum, as is true in this case. The diffuse eruption can sometimes be mistaken for a sudden increase in the number of molluscum lesions, but the papular dermatitis lesions do not have the flat-topped dome-shape nor white centers.³ On average, the id reaction lasts about 6 weeks, after which both it and the primary molluscum lesions typically resolve.³ Although not seen in this case, more than a third of molluscum patients develop a pruritic, erythematous, eczematous area around molluscum lesions, termed molluscum dermatitis or eczema molluscatum, which may be more prominent than the molluscum itself.³ The eczematous patch typically surrounds molluscum lesions but also may occur at distant sites.¹² This reaction is especially common in patients with atopic dermatitis, 51% of whom develop it.³ It is considered a hypersensitivity reaction and may be asymptomatic or minimally pruritic.¹² Molluscum dermatitis suggests that the immune system has taken notice of the infection and is fighting it¹³; however, it does not necessarily indicate impending resolution.³

Differential diagnosis

The differential diagnosis for molluscum includes herpes simplex, warts, and milia.¹⁴ Like molluscum, herpes simplex lesions can have central umbilication, but the lesions are vesicular rather than solid. Warts typically have a rough, jagged surface in contrast to the smooth surface of molluscum lesions. Milia tend to be smaller and not flat topped. They are more common in infants and adults than in children and primarily affect the face.

Inflamed molluscum lesions and molluscum dermatitis can be mistaken for atopic dermatitis, and molluscum-associated id reactions may exacerbate atopic dermatitis. Inflamed molluscum and molluscum with id reaction could be confused with scabies, which may become crusted and also may be accompanied by id reaction. Presence of serpiginous linear burrows would suggest scabies rather than molluscum, and the diagnosis of scabies can be confirmed by scraping a burrow and looking for a mite or its feces under a microscope.

Prognosis and treatment

Molluscum infections typically resolve spontaneously in months to years (average duration, 13 months),¹⁴ so treatment may not be required. The goal of treatment is to accelerate the resolution of the infection, but some studies have found that common treatments may not shorten the time to resolution.¹¹ However, if there is substantial pruritus, lesions are cosmetically undesirable, or a child has atopic dermatitis and is at increased risk for autoinoculation, treatment may be warranted.¹⁵ Furthermore, molluscum lesions can scar, so prevention of autoinoculation may help minimize scarring.¹⁶

Few high-quality studies of the efficacy of molluscum treatments exist, and a 2009 Cochrane review found insufficient evidence to recommend any therapy for molluscum. The most common treatment used by pediatric dermatologists is cantharidin,¹⁷ and this treatment also is available to primary care practitioners. This option is preferred over other destructive methods such as curettage or liquid nitrogen cryotherapy because it is not painful or traumatic and is well tolerated by pediatric patients.⁸ Parent and physician satisfaction with the therapy is high; 78%-95% of parents would use cantharidin treatment again for molluscum recurrence.^4,8,18 Originally extracted from the blister beetle but now synthesized commercially,¹⁹ cantharidin causes vesiculation at the dermoepidermal junction6 by destroying intercellular connections.4 Vesiculation of the skin causes extrusion of the molluscum body, which facilitates resolution of the lesion.¹⁹ The cantharidin formulation is applied directly to molluscum lesions with the wooden end of a cotton-tipped applicator.⁴ Patients may be directed to wash it off after 4-6 hours. Blistering is an expected, desired outcome. A minority of patients may experience mild temporary pain (7%), more significant blistering (2.5%), burning (less than 1%), pruritus (less than 1%), or irritation (less than 1%).⁴ There is a risk of scarring and pigmentary changes, but these risks also exist for untreated lesions.¹⁹ Cantharidin treatment is repeated approximately every 4 weeks, and 90% of cases resolve after an average of 2.1 treatments.¹⁸ Topical retinoids can be used in an attempt to trigger an irritant response by the immune system, and they are the preferred therapy for facial lesions, but they are inconsistently effective.4 Randomized controlled trials found that imiquimod, a previously popular treatment is not effective,²⁰ and the evidence for cimetidine is contradictory.^21,22 Molluscum dermatitis and id reaction can be treated with medium strength topical steroids. 

References

1. Viral diseases of the skin, in "Hurwitz Clinical Pediatric Dermatology," 4 ed. (New York: Elsevier, 2011, pp. 348-69). .
2. Molluscum, in "Red Book Report of the Committee on Infectious Diseases," 2015.

Ms. Haddock is a medical student at the University of California, San Diego, and a research associate at Rady Children's Hospital-San Diego. Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children's Hospital-San Diego and professor of dermatology and pediatrics at the University of California, San Diego. Dr. Eichenfield and Ms. Haddock state they have no relevant financial disclosures.

By Ellen S. Haddock, MBA, and Lawrence F. Eichenfield, MD

Molluscum

Molluscum typically presents as smooth, flesh-colored, flat-topped papules 2-8 mm in diameter with central whitish area, which is composed of the causative molluscum pox virus. While central depressions called umbilications are common, they may not be present in early molluscum lesions.^1,2 Lesions most often occur on the trunk and arms, but can occur anywhere.3-5 Individuals usually have multiple lesions, which may be clustered especially in areas of skin-to-skin contact.^5,6 Molluscum lesions can be itchy.

Molluscum is a benign viral skin infection caused by the molluscum contagiosum virus, which is a member of the poxvirus family. Molluscum infections are common, affecting 5%-11% of children.^5,7 Molluscum most often affects children younger than 8-years-old,⁵ with an average age of 5.8 years.⁸ The infection is spread through skin-to-skin contact with other individuals and by autoinoculation, which means that the infection can be spread from one area of an individual's skin to another when he or she scratches a lesion and then touches another area. It also can be spread by contact with fomites like towels and sponges.1 An association between public swimming pool use and molluscum infection has been reported, but this may have more to do with shared towels and equipment like kick-boards than transmission through the water itself.9 Molluscum sometimes is spread through contact sports like wrestling⁶ and between children sharing a bath.⁹ In adults, in whom molluscum is much less common because of acquired immunity,10 molluscum may be sexually transmitted or associated with HIV; however, this is rarely the case in children.¹

Children with atopic dermatitis have increased risk of molluscum infection in part because breaks in their skin and pruritus facilitate autoinoculation through scratching.¹¹ Not uncommonly, molluscum lesions become inflamed, with tenderness, erythema, and crust. In a study by Berger et al., 22% of patients had inflamed molluscum lesions.³ The appearance of inflamed molluscum lesions may raise concern about bacterial infection, but more often, the inflammation is a sign that the immune system is reacting to the viral infection and has almost "won the battle."¹⁰ After inflamed molluscum lesions develop, the total number of molluscum lesions typically declines,3 and some consider inflamed molluscum lesions to be a "beginning of the end sign," indicating that the infection may soon resolve.¹⁰ If the child is afebrile, lesions are itchy and painless, skin culture is negative, and there is no lymphangitis or spreading erythema, the inflammation is more likely a sign of impending resolution than bacterial secondary infection, and the urge to prescribe antibiotics should be resisted.¹⁰

As seen in this case, some patients with molluscum (5%) develop a diffuse, monomorphous, papular, or papulovesicular eruption that is an id reaction.3 This may appear to be eczema-like, lichenoid in appearance, or mimicking Gianotti-Crosti syndrome (papular acrodermatitis of childhood).³ It typically affects the arms and legs, is bilateral, and may be pruritic. The id reaction may occur in conjunction with inflamed molluscum, as is true in this case. The diffuse eruption can sometimes be mistaken for a sudden increase in the number of molluscum lesions, but the papular dermatitis lesions do not have the flat-topped dome-shape nor white centers.³ On average, the id reaction lasts about 6 weeks, after which both it and the primary molluscum lesions typically resolve.³ Although not seen in this case, more than a third of molluscum patients develop a pruritic, erythematous, eczematous area around molluscum lesions, termed molluscum dermatitis or eczema molluscatum, which may be more prominent than the molluscum itself.³ The eczematous patch typically surrounds molluscum lesions but also may occur at distant sites.¹² This reaction is especially common in patients with atopic dermatitis, 51% of whom develop it.³ It is considered a hypersensitivity reaction and may be asymptomatic or minimally pruritic.¹² Molluscum dermatitis suggests that the immune system has taken notice of the infection and is fighting it¹³; however, it does not necessarily indicate impending resolution.³

Differential diagnosis

The differential diagnosis for molluscum includes herpes simplex, warts, and milia.¹⁴ Like molluscum, herpes simplex lesions can have central umbilication, but the lesions are vesicular rather than solid. Warts typically have a rough, jagged surface in contrast to the smooth surface of molluscum lesions. Milia tend to be smaller and not flat topped. They are more common in infants and adults than in children and primarily affect the face.

Inflamed molluscum lesions and molluscum dermatitis can be mistaken for atopic dermatitis, and molluscum-associated id reactions may exacerbate atopic dermatitis. Inflamed molluscum and molluscum with id reaction could be confused with scabies, which may become crusted and also may be accompanied by id reaction. Presence of serpiginous linear burrows would suggest scabies rather than molluscum, and the diagnosis of scabies can be confirmed by scraping a burrow and looking for a mite or its feces under a microscope.

Prognosis and treatment

Molluscum infections typically resolve spontaneously in months to years (average duration, 13 months),¹⁴ so treatment may not be required. The goal of treatment is to accelerate the resolution of the infection, but some studies have found that common treatments may not shorten the time to resolution.¹¹ However, if there is substantial pruritus, lesions are cosmetically undesirable, or a child has atopic dermatitis and is at increased risk for autoinoculation, treatment may be warranted.¹⁵ Furthermore, molluscum lesions can scar, so prevention of autoinoculation may help minimize scarring.¹⁶

Few high-quality studies of the efficacy of molluscum treatments exist, and a 2009 Cochrane review found insufficient evidence to recommend any therapy for molluscum. The most common treatment used by pediatric dermatologists is cantharidin,¹⁷ and this treatment also is available to primary care practitioners. This option is preferred over other destructive methods such as curettage or liquid nitrogen cryotherapy because it is not painful or traumatic and is well tolerated by pediatric patients.⁸ Parent and physician satisfaction with the therapy is high; 78%-95% of parents would use cantharidin treatment again for molluscum recurrence.^4,8,18 Originally extracted from the blister beetle but now synthesized commercially,¹⁹ cantharidin causes vesiculation at the dermoepidermal junction6 by destroying intercellular connections.4 Vesiculation of the skin causes extrusion of the molluscum body, which facilitates resolution of the lesion.¹⁹ The cantharidin formulation is applied directly to molluscum lesions with the wooden end of a cotton-tipped applicator.⁴ Patients may be directed to wash it off after 4-6 hours. Blistering is an expected, desired outcome. A minority of patients may experience mild temporary pain (7%), more significant blistering (2.5%), burning (less than 1%), pruritus (less than 1%), or irritation (less than 1%).⁴ There is a risk of scarring and pigmentary changes, but these risks also exist for untreated lesions.¹⁹ Cantharidin treatment is repeated approximately every 4 weeks, and 90% of cases resolve after an average of 2.1 treatments.¹⁸ Topical retinoids can be used in an attempt to trigger an irritant response by the immune system, and they are the preferred therapy for facial lesions, but they are inconsistently effective.4 Randomized controlled trials found that imiquimod, a previously popular treatment is not effective,²⁰ and the evidence for cimetidine is contradictory.^21,22 Molluscum dermatitis and id reaction can be treated with medium strength topical steroids. 

References

1. Viral diseases of the skin, in "Hurwitz Clinical Pediatric Dermatology," 4 ed. (New York: Elsevier, 2011, pp. 348-69). .
2. Molluscum, in "Red Book Report of the Committee on Infectious Diseases," 2015.

Ms. Haddock is a medical student at the University of California, San Diego, and a research associate at Rady Children's Hospital-San Diego. Dr. Eichenfield is chief of pediatric and adolescent dermatology at Rady Children's Hospital-San Diego and professor of dermatology and pediatrics at the University of California, San Diego. Dr. Eichenfield and Ms. Haddock state they have no relevant financial disclosures.