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Skin-nontumor / Clinical Dermatology

Infectious disorders

Parvovirus B19


Reviewer: Mowafak Hamodat MB.CH.B, MSc., FRCPC (see Reviewers page)
Revised: 5 September 2011, last major update September 2010
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Definition
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● Viral infection that typically causes mild rash in children

Terminology
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● Clinical syndrome is called "Fifth disease" or erythema infectiosum

Etiology
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● Parvovirus B19 is spread by respiratory droplets, and has an incubation period of 5-14 days
● The viral receptor is the erythrocyte P antigen, which is expressed on endothelial cells
● Parvovirus attacks erythroblasts, may cause acute anemic crisis in patients with accelerated erythropoiesis, immunocompromise or minimal reserve (chronic anemia, hemolytic anemia, sickle cell, fetuses), although usually recipients have no symptoms (Transfusion 2005;45:1811)
● Pregnant women may pass virus to fetus, where it may cause marked fetal anemia and hydrops
● Rash may be due to delayed type hypersensitivity, antibody dependent cellular immunity against microbial antigens in epidermis or endothelium, or circulating immune complexes

Clinical features
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● Causes “Fifth” disease in children, a mild illness with a “slapped cheek” facial rash
● Characteristic skin manifestations are petechial eruption in a glove and stocking distribution, reticular truncal erythema, and "slapped cheek" sign (Hum Pathol 2000;31:488)
● May produce influenza-like illness, miscarriage, fetal hydrops and neonatal angioedema
● Atypical presentations include generalized petechial rash (Pediatrics 2010;125:e787), asymptomatic papular eruption or lower extremity palpable purpura, red baby syndrome (Indian J Pediatr 2009;76:309), papular purpuric gloves and socks syndrome (Med Oral Patol Oral Cir Bucal 2007;12:E4); may resemble Sweet’s syndrome, myopathic dermatomyosis or lupus (Intern Med 1998;37:708)
● Immune response usually clears infection and provides lifelong protection, but virus may persist in blood or tissue (Transfus Med 2007;17:263)
● Parvovirus B19 has been associated with some cases of Rosai-Dorfman disease (J Clin Pathol 2006;59:1320)

Clinical images
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“Slapped cheek” appearance

Micro description
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● Interstitial histiocytic infiltrate with piecemeal fragmentation of collagen and mononuclear cell-predominant vascular injury pattern
● Extravasated red blood cells
● Erythrocyte precursors may have intranuclear inclusions
● Eosinophils and occasional neutrophils may be present
● Perineuritis may also be present
● Also interface dermatitis, eczematous alterations, papillary dermal edema; occasionally mesenchymal mucinosis, leukocytoclastic vasculitis

Micro images
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Bone marrow          Placenta                    Fetal spleen


B19 immunostain

Positive stains
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● B19 immunostain

Molecular / cytogenetics
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● Virus identified in endothelial cells of lesional skin by several methods, including PCR
● Also identified in keratinocytes

Additional references
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PathologyOutlines.com-Bone Marrow chapter, eMedicine

End of Skin-nontumor / Clinical Dermatology > Infectious disorders > Parvovirus B19


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