Gianotti-Crosti syndrome is a type of childhood exanthem that is self-limiting, has a characteristic acral distribution and is rarely accompanied by systemic findings.
Gianotti-Crosti syndrome (GCS) is a sudden onset of rash in children aged 15 months to 2 years that may be associated with immunization or an acute infectious disease. The most common inciting factor in GCS is infection with Epstein-Barr virus (EBV). Although GCS is usually asymptomatic, it may cause mild pruritus. The rash lasts from 2 to 4 weeks but can be present for as long as 4 months. Recurrent episodes are rare  .
In general, children affected with GCS do not appear to be ill but have multiple discrete papular and papulovesicular eruptions on the cheeks, extensor surfaces of the extremities and the buttocks. The distribution is symmetrical and acral. The individual monomorphous papules range from 1 to 5 or 10 millimeters and can have a range of color from flesh-toned to erythematous to red-brown. They have a flat top and may coalesce to form larger plaques. However, development of a petechial or purpuric appearance is uncommon. The papules may acquire a lichenoid appearance over days to weeks. It usually resolves after 10 to 60 days but new lesions may appear for 8 to 11 weeks  . One report has shown that all cases with an exclusive eruption on the face were infected with EBV .
The most important etiologic factor is an infection but immunomodulation can further accentuate the condition and this explains the association of GCS with vaccination .
Other physical findings on examination may include fever (27%), lymphadenopathy (31%), hepatosplenomegaly (4%), and oropharyngeal vesicles or ulcers, pharyngeal erythema, or tonsillar swelling. Axillary or inguinal adenopathy, hepatosplenomegaly, and an extensive involvement of the trunk are considered as inconsistent findings in GCS.
The proposed diagnostic criteria for GCS is as follows  :
Laboratory studies are generally not needed to diagnose GCS but the presence of jaundice or hepatomegaly should raise suspicion of hepatitis B virus infection and tests may reveal elevated liver enzymes, although elevated liver enzymes are mostly related to EBV infection.
Findings on skin biopsy can help rule out other conditions since they are not specific for GCS. Focal spongiosis, mild acanthosis, parakeratosis, and psoriasiform hyperplasia can be observed in the epidermis . The dermis shows moderate perivascular infiltrate of lymphocytes and histiocytes, while eosinophils are scattered occasionally . The papillary dermis reveals extravasated erythrocytes .