The differential 'Slaps' you in the face

When one talks about approach to new polyarthritis in the ER the differential diagnosis is quite extensive but should include.......

Infectious:

• viral (see below)
• bacterial (disseminated gonococcal, endocarditis...)
• lyme disease
• fungal

Inflammatory:

• SLE, RA, Stills Disease, IBD, psoriatic
• Sarcoidosis (Lofgrens)
• serum sickness reaction
• acute rheumatic fever

Finally....Always important to remember a bit about parvovirus B19 and the various clinical presentations.....

Erythema Infectiosum (5th disease)

• Incubation 4-28 days
• Prodrome: low grade fever, h/a, mild URTI
• Characteristic rash (3 phases): Slapped cheek appearance (facial flushing), Diffuse macular erythema, Central clearing of macular lesions – lacy, reticulated appearance
• Rash disappears over 1-3 wks but can wax and wane (sun exposure, exercise, heat, stress)

Arthropathy

• Females > males, adolescents > children
• likely post-infectious resolves in 2-4 wks
• range in symptoms from arthralgia with morning stiffness to frank arthritis
• most common: hands, writsts, knees, ankles

Aplastic crisis

• Transient arrest of erythropoiesis and absolute reticulocytopenia – sudden fall in hemoglobin in pts with chronic hemolysis (RBC life shorter)
• Incubation period for transient aplastic crisis is shorter – occurs coincident with viremia

Chronic Anemia:

• Immunocompromised

Fetal Infection:

• Nonimmune fetal hydrops and intrauterine fetal demise, risk fetal loss
• Monitor for signs of fetal anemia / hydrops – U/S with Doppler to measure peak systolic flow velocity in MCA

Myocarditis:

• Rare cause of lymphocytic myocarditis

Other cutaneous:

• PPGSS – papular-purpuric gloves and stocking syndrome – fever, pruritis and painful edema extremities