Characterizing Viral Exanthems

Joseph M Lam


Pediatr Health. 2010;4(6):623-635. 

In This Article

Papular Exanthems

Papular Acrodermatitis of Childhood

Papular acrodermatitis of childhood (PAC), also known as Gianotti–Crosti syndrome (GCS), is a unique cutaneous disorder characterized by the abrupt onset of an erythematous papular exanthem found on the extremities, buttocks and face (Figure 5). It is a relatively common dermatosis, seen worldwide, primarily affecting children between 2 and 6 years of age.

Figure 5.

Lichenoid monomorphic papules on the extensor upper extremity.

Papular acrodermatitis of childhood was first described by Gianotti in 1953, in a young child with a monomorphous erythematous papular rash confined to the extensor surfaces of the arms and legs.[48] After finding hepatitis B surface antigen in the serum of affected children, it was believed that PAC was solely a manifestation of hepatitis B infection.[49] However, subsequently, EBV has become recognized as the most common viral agent associated with GCS in the USA.[50] However, many other viruses and infectious agents have been associated with PAC, and these include hepatitis A virus, CMV, human herpesvirus, Coxsackie virus A16, B4 and B5, rotavirus, parvovirus B19, molluscum contagiosum (MC), respiratory syncytial virus, mumps virus, and parainfluenza virus type 1 and 2.[48]

The pathogenesis of GCS is still unclear but probably reflects a recognizable reactive pattern in response to diverse infectious stimuli. Clinically, PAC usually presents with symmetrical monomorphous papular or papulovesicular exanthem over the cheeks, extensor aspects of the extremities and gluteal areas. Occasionally, the papules coalesce into larger plaques and become hemorrhagic or form scales. The trunk, elbows and knees are usually spared; lesions typically fade within 3–4 weeks.

The diagnosis is made clinically, and a recent study proposed clinical criteria for the diagnosis of PAC (Box 1).[51,52] The differential diagnosis includes varicella, Henoch–Schönlein purpura, arthopod bites, scabies and MC. Treatment is usually unnecessary as the disease is self-limiting.

Molluscum Contagiosum

Molluscum contagiosum is a highly contagious viral infection of the mucous membranes and skin, commonly seen in children. It is caused by a poxvirus of the genus Molluscipoxvirus. It usually presents as pearly umbilicated skin-colored dome-shaped papules, which usually range from 2 to 8 mm in size (Figure 6). In approximately 30% of patients, an eczematous reaction may encircle lesions.[53] Patients with immunodeficiency, including AIDS and leukemia, may be more likely to develop extensive disease.[54] MC is transmitted by close physical contact, fomites and autoinoculation. Shared bathtubs, pools and towels may facilitate spread of the MC virus.

Figure 6.

Pearly umbilicated skin-colored dome-shaped papules over the posterior leg.

The diagnosis is made clinically, but Wright or Giemsa staining of cells expressed from the central core of lesions will reveal characteristic intracytoplasmic inclusions. A Tzanck stain can also be done to highlight the typical pattern of numerous discrete ovoid intracytoplasmic inclusion bodies, known as molluscum bodies.

The differential diagnosis includes juvenile xanthogranuloma, verruca plana, milia and papular urticaria. Lesions usually resolve spontaneously, but this process may take years, with more prolonged illness in the immunocompromised patient. Reasons for actively treating MC may include alleviating discomfort and itching, limitating spread to other areas and people, preventing scarring and superinfection, and eliminating the social stigma of visible lesions. No single intervention has been shown to be convincingly effective in the treatment of MC.[55] Treatment options include destructive, immune-enhancing or antiviral modalities.

Gentle local destruction is the typical approach for treating MC, and cantharidin is a safe and effective therapy for MC in children; it is extremely effective and well tolerated, with high parental satisfaction if used in experienced hands.[53] Benefits include painless application and high efficacy rates of up to 90%.[54] Other destructive therapies include curettage, liquid-nitrogen cryotherapy and peeling agents, such as lactic acid or topical retinoids. Immune-enhancing agents speed up the immune clearance of MC infection, and these include topical imiquimod, oral cimetidine and intralesional Candida antigen.[56] Antivirals, such as cidofovir, have been used in pediatric patients with HIV-1 for the treatment of disseminated MC recalcitrant to conventional therapy.[57,58]


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