Epstein-Barr virus is the cause of classic infectious mononucleosis. Other infections may mimic Epstein-Barr virus infectious mononucleosis, for example, cytomegalovirus, human herpes virus-6, toxoplasmosis, lymphoma, cat scratch fever, and rubella. Parvovirus B19 infections in children present as febrile exanthems; adults usually have small joint arthritis.

Parvovirus B19 presents as a “flu-like” illness with low-grade fever, fatigue, malaise, and later, a rash may appear on the face (“slapped cheeks” appearance), trunk, or extremities (sparing the palms and soles) and is often accompanied/followed by small joint arthritis, which may be intermittent/persistent.Cervical adenopathy is rare in adults. The differential diagnosis of Parvovirus B19 depends on its clinical manifestations. Adults with rash and small joint arthritis may mimic rubella. Parvovirus B19 immunoglobulin M (IgM) antibodies may cross-react with rubella IgM antibodies.Rash with cervical adenopathy occur with Epstein-Barr virus infectious mononucleosis, cytomegalovirus, or toxoplasmosis.Fatigue with cervical adenopathy suggests lymphoma, cat scratch disease, Epstein-Barr virus, or cytomegalovirus.False-positive Monospot tests may occur with rubella, toxoplasmosis, cytomegalovirus, Epstein-Barr virus, and Parvovirus B19.We present a case of adult Parvovirus B19 mimicking Epstein-Barr virus infectious mononucleosis.

Case Report

A 36-year-old woman presented with sore throat, fever, fatigue, and truncal rash. Throat culture was positive for group A streptococci. Physical examination was unremarkable except for bilateral posterior/anterior cervical adenopathy and tenderness of the interphalangeal joints. Laboratory testing included a white blood cell count of 5.2 K/mm3 (neutrophils = 60%, lymphocytes = 24%, monocytes = 12%, and eosinophils = 4%) and an erythrocyte sedimentation rate of 5 mm/h. Serum transaminases were unelevated. Epstein-Barr virus viral capsid antigen IgM titer was negative, and Epstein-Barr virus viral capsid antigen immunoglobulin G (IgG) and nuclear antigen titers were positive. Cytomegalovirus IgM and IgG titers were negative. Rubella, human herpes virus-6, and Coxsackie B IgM and IgG titers were negative. Rheumatoid factors were not present, and her antinuclear antibody titer was negative. The antistreptolysin O titer was 93 IU/mL (n = <200 IU/mL). The Parvovirus B19 IgM titer was 12.0 IU (n = <0.8 IU) and IgG titer was 1.4 IU (n = 0.8 IU). After a few months, her cervical lymphadenopathy and hand arthralgias resolved, but her fatigue persisted. She then recalled that her illness started 5 months before, during late winter, following a viral illness in her children.