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AKA fifth disease; AKA “slapped cheek disease”
| • | small outbreaks of fifth disease usually occur in spring |
| • | one infection gives lifelong immunity (like most viruses) |
clinical:
| • | the exanthem develops suddenly without prodromal symptoms |
| • | fever is absent or slight |
| • | “slapped cheeks” = hot, turgid erythema, almost erysipelatoid |
| • | generalized fish-net-like eruption (reticular) follows (a unique characteristic) |
| • | rash fades without scaling or pigmentation; but may reappear during next 2-3 weeks |
| • | in most children the rash recurs after its initial resolution , usually associated with sun exposure, hot bath, or physical activity |
| • | recurrent episodes may be seen for weeks or months following infection |
| • | recurrence of rash is not associated with recurrent viremia |
| • | adults in the same families may present with disabling arthralgia or synovitis of the large joints (arthritis and pruritis) |
etiology = Parvovirus B19
| • | spread is by droplets of the nasopharynx |
| • | the major target of parvovirus is the bone marrow erythroid progenitor cell |
| • | the virus is cytotoxic for these cells which causes a halt in red cell production |
| • | the exanthem and polyarthralgia are the result of antibody/antigen immune complexes and occur as bone marrow recovery is under way |
| • | polyarthralgia is often the predominant symptom of parvovirus B19 infection in adults (see also RASH AND ARTHRITIS). |
| • | B19 infection during pregnancy may result in fetal infection in approximately 30% of pregnancies, but only 9% of infected fetuses have a poor outcome (other studies have suggested that the fetal risk is even lower) |
| • | in effect, the B19 infected fetus develops an aplastic crisis resulting in high output cardiac failure and associated soft-tissue edema, ascites, pleural effusions, and in some cases, polyhydramnios, that is nonimmune hydrops fetalis |
| • | infected fetuses have been successfully treated in utero by transfusion with excellent salvage and outcome |
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