Papular acrodermatitis or Gianotti-Crosti syndrome is a benign rash that occurs in childhood in association with a wide variety of viral illnesses. While historically thought to be a manifestation of hepatitis B infection, it has been demonstrated to occur following many viral illnesses and vaccination, which suggests that this is an immunologic response rather than a primary manifestation of infection.
When papular acrodermatitis was initially described in the 1950s, it was proposed as a manifestation of the hepatitis B virus infection. In the post-hepatitis B vaccination era, physicians do not see this association as often. Ongoing studies have demonstrated that papular acrodermatitis can occur following a wide variety viruses. These viruses include but are not limited to Epstein-Barr virus, cytomegalovirus, coxsackievirus, adenovirus, influenza, enteroviruses, echovirus, hepatitis A virus, herpes simplex viruses, HHV-6, HIV, mumps, parainfluenza virus, parvovirus B19, poxviruses, respiratory syncytial virus, and rotavirus. Additionally, it has been reported after vaccination, including influenza, Calmette-Guerin bacillus, diphtheria-pertussis-tetanus, poliomyelitis, hepatitis B, Japanese encephalitis, and measles vaccines. The Epstein-Barr virus is the most commonly reported cause of papular acrodermatitis in the United States. In many cases, no infectious trigger is identified. The relationship between these potential triggers and the manifestation of papular acrodermatitis is not well defined but is presumed to be immunologically mediated.
Reports of papular acrodermatitis are most common in children younger than four years of age, which is consistent with its viral etiology. In children, there is no sex predilection; however, in adulthood, it is slightly more common in female patients. In papular acrodermatitis, there does not appear to be a genetic or familial predisposition. Most cases occur in spring and summer. Papular acrodermatitis occurs more often in children with atopic diseases, including atopic dermatitis. Although the disease is observed worldwide, the etiological agents exhibit geographic variations.
The precise pathophysiology of papular acrodermatitis is unknown, but it is presumed to be immunologically mediated given its association with viral infections and vaccination. Its increased prevalence in patients with a history of atopic disease, family history of atopic disease, and/or elevated immunoglobulin E also supports an immune-mediated pathology. Proposed processes include immune complexes or delayed hypersensitivity reactions, but to date, this has not been well defined.
Papular acrodermatitis clinically manifests as a papular rash in the acral distribution, as its name implies. Fever, lymphadenitis, and other symptoms such as hepatosplenomegaly or pharyngitis may be seen in association with the rash or preceding it. This is consistent with a variety of viral triggers for this entity. There also may be a history of vaccination preceding the onset of the rash. The rash is abrupt in onset.
Papular acrodermatitis is a symmetrical, monomorphous, papular eruption that is observed most commonly on the extensor surfaces of the extremities; however, the rash may also affect the face and buttocks. Palms and soles may also be involved. Arms are more commonly involved than legs. The trunk and scalp are relatively spared, as are the popliteal and antecubital fossae. However, the involvement of any of these areas does not preclude the diagnosis of papular acrodermatitis. The rash may be pruritic. Symptoms frequently last for 2 to 4 weeks. In some cases, new lesions may continue to appear for up to 8 to 11 weeks after onset of illness. The lesions are usually pale pink to flesh-colored and 1 mm to 10 mm in size. The lesions tend to be larger in younger children and smaller in older children and adolescents. Rarely, lesions may be vesicular or hemorrhagic. They are firm and discrete. Rarely, the lesions can become confluent over pressure points like knees and elbows. Koebner phenomena, with the accentuation of lesions at the site of trauma, has also been reported. There is not an associated mucosal enanthem. Importantly, the appearance of the rash itself may not help to distinguish the variously associated etiologies of papular acrodermatitis; however, careful assessment of associated or antecedent symptoms is essential for recognizing possible infectious triggers that may require further evaluation or isolation. Usually, the rash resolves without any residual effects or scarring. Occasionally, hyperpigmentation or hypopigmentation may persist after the rash resolves.
The differential diagnosis of papular acrodermatitis includes mainly other viral exanthems, insect bites, atopic dermatitis, erythema multiforme, Langerhans cell histiocytosis, and lichenoid dermatoses. In general, papular acrodermatitis is a clinical diagnosis with no laboratory testing indicated unless there are symptoms or physical exam findings, such as hepatomegaly, to suggest an underlying viral illness, such as hepatitis, that may require further management. Diagnostic criteria have been proposed and include the following symptoms:
Practitioners also may need to further evaluate the causative virus in children who are immunocompromised or who reside in immunocompromised areas. If a patient presents with jaundice, hepatomegaly, or generalized lymphadenopathy, evaluation for other viral infections, including hepatitis B, may be indicated. Rarely, a skin biopsy may be performed to exclude other conditions in immunocompromised or other high-risk patients. Normally, biopsy findings are non-specific, with dermal perivascular mononuclear cell infiltrates and capillary endothelial swelling.
Practitioners should reassure patients that papular acrodermatitis on its own is a benign and self-limited illness. Symptomatic management of itching may be helpful. Patients may use emollients or oral antihistamines. Mild to moderate potency topical steroids may be used in patients who fail to achieve relief of itching with emollients and oral antihistamines, as infectious agents do not directly cause the skin lesions. However, treatment with topical steroids or oral antihistamines does not shorten the course of illness. Any underlying disorder, such as hepatitis B, that requires further management should be addressed. Lesions resolve without scarring, although hyperpigmentation may persist in some patients.
Papular acrodermatitis is not person-to-person transmissible and does not require isolation beyond standard precautions or restriction from school or other community activities. However, the associated viral infection may be contagious thus isolation may need to be considered based on other symptoms suggestive of infectious disease.