A perplexing red eruption

THE CASE

Perplexed parents ask you to evaluate their healthy 12-month-old girl, who awoke this morning with an asymptomatic juicy red papular eruption on her cheeks. Other than a few days of loose stools last week, she has been well. She was vaccinated against hepatitis B one month ago.

DIAGNOSIS:

EPIDEMIOLOGY

GCS affects children between 6 months and 6 years, with peak incidence from 1 to 6 years of age. There have also been scattered case reports of GCS in adults. Additionally, GCS is also associated with an increased incidence of a personal or family history of atopy.²

ETIOLOGY AND PATHOGENESIS

GCS was initially described in association with hepatitis B viral (HBV) infection. However, with the increase in HBV immunizations and decrease in HBV infection, Epstein-Barr virus (EBV) is now recognized as the most common cause worldwide. GCS is also purported to be a cutaneous reaction pattern associated with other viruses, bacteria, and vaccines.

The pathogenesis of GCS is unclear. Various hypotheses attribute the development of GCS to viral antiginemia with circulating immune complexes, or a virus-induced delayed hypersensitivity reaction. As neither viral particles nor viral antigens have been demonstrated in the skin lesions of GCS, current belief is that the mechanism of lesion development does not involve a direct local interaction between viral antigens and immunocompetent cells in the skin.³

CLINICAL FEATURES

GCS may be accompanied by a nonspecific prodrome of upper repiratory tract infection, diarrhea, or pharyngitis. Patients typically present with an abrupt onset of multiple, monomorphous flat-topped or dome-shaped edematous papules or papulovesicles. Confluence of papules may lead to appearance of edematous plaques, especially on the elbow. The pink to red-brown papules are symmetrically distributed on the cheeks, extensor surface of the extremities, and buttocks. The trunk, knees, elbows, palms, and soles are usually spared, but may reveal a few lesions. The eruption may be pruritic and rarely hemorrhagic.

Lesions last for at least 10 days and up to four to six weeks.¹ Lymphadenopathy (especially of the cervical, axillary, and inguinal chains) can be found in one third of patients. Additionally, a Koebner phenomenon (development of lesions in areas of trauma) may be observed in the early stages of the disease.

DIFFERENTIAL DIAGNOSIS

The clinical presentation of GCS is distinct, but atypical or resolving lesions may be confused with other cutaneous diseases.

Papular urticaria or insect bite hypersensitivity reaction presents with crops of pruritic papules or papulovesicles with a predilection for the extensor surfaces of the extremities. Unlike GCS, papular urticaria commonly involves the trunk. There may also be a central punctum indicative of an insect bite.

Lichen planus (LP) is another possibility; however, this purple, pruritic, polygonal popular eruption prefers the volar wrists, lower legs, and ankles. In contrast to GCS, LP rarely involves the cheeks. While there is no mucosal involvement in GCS, LP can manifest with white reticulated patches, or plaques on the buccal mucosa.

Lichenoid drug reactions should also be considered. These eruptions have been reported in association with gold, antimalarial agents, ß-blockers, and diuretics. However, this is a rare occurrence in children, and truncal involvement is common.

The differential diagnosis would also include the early papular lesions of erythema multiforme, scabies (given the predominantly acral distribution), and pityriasis rosea.