Laboratory Studies
No specific laboratory blood tests are required for asymmetric periflexural exanthem of childhood (APEC). Asymmetric periflexural exanthem of childhood may be accompanied by an elevated erythrocyte sedimentation rate. Occasionally, serologic results are positive for respiratory pathogens such as adenovirus and parainfluenza virus.
Asymmetric periflexural exanthem of childhood has been reported in a 3-year-old girl following an upper respiratory tract infection and the onset of axonal Guillain-Barré syndrome (acute motor axonal neuropathy).
Parvovirus B19 has been associated with asymmetric periflexural exanthem of childhood in several children and one adult. Most studies have revealed negative serologic results for hepatitis, borreliosis, Mycoplasma organisms, Epstein-Barr virus, cytomegalovirus, parvovirus B19, HIV, coxsackievirus, toxoplasmosis, and rickettsiae.
Histologic Findings
Biopsy is uncommonly performed for asymmetric periflexural exanthem of childhood.
When obtained, microscopic examination reveals a superficial and deep perivascular, interstitial, and periadnexal lymphohistiocytic infiltrate in the dermis. This finding may also be accompanied by epidermal spongiosis and lymphocytic infiltration of the epidermal portion of the eccrine ducts.
See the images below.

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Morbilliformlike eruption in a child with involvement of the axilla, lateral thorax, and abdomen. Used with permission from McCuaig et al (1996) from the Journal of the American Academy of Dermatology.
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Eczematouslike eruption with a predominantly hemicorporeal distribution photographed on the eighth day after initial appearance of lesions. Used with permission from Bodemer and de Prost (1992) from the Journal of the American Academy of Dermatology.
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Pattern of reticulated plaques on the posterior lower limb of a child. Used with permission from McCuaig et al (1996) from the Journal of the American Academy of Dermatology.
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Histopathologic slide demonstrates perivascular, interstitial, and periadnexal infiltrate of lymphocytes and histiocytes in the deep dermis (hematoxylin-phloxine-saffron stain). Used with permission from McCuaig et al (1996) from the Journal of the American Academy of Dermatology.
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Histopathologic slide demonstrates epidermal spongiosis and lymphocytic infiltration of the intraepidermal portion of an eccrine duct (hematoxylin-phloxine-saffron stain). Used with permission from McCuaig et al (1996) from the Journal of the American Academy of Dermatology.