Incidence of Rheumatic Fever
Rheumatic fever is an inflammatory disease which may affect the:
Strep Throat and Rheumatic Fever
Rheumatic fever develops as a consequence of infection with group A streptococcus. Most commonly, the streptococcus infection is located in the upper respiratory tract such as strep throat or as scarlet fever.
The connection between strep throat and rheumatic fever was not realized until the late 19th century. The development and availability of antibiotics in the 20th century is credited for the diminishing frequency of rheumatic fever. Rheumatic fever is not uncommon throughout the world, especially in developing countries, but is less common in the United States since the early 20th century. According to the Merck Manual, the incidence of rheumatic fever in the United States is approximately 1/100,000.
Rheumatic fever can occur at any age but primarily affects children from 5 years old to 15 years old. Rheumatic fever develops about 20 days after strep throat or scarlet fever. The streptococcus infection which leads to rheumatic fever may be asymptomatic in a third of all cases.
Jones Criteria for Diagnosis of Rheumatic Fever
In 1944, the "Jones criteria" provided guidelines for the diagnosis of rheumatic fever. The guidelines, which have been revised and modified, are still used today. In addition to previous infection with streptococcus (i.e. positive throat culture, rising ASO titer), the diagnosis of rheumatic fever requires the presence of 2 major Jones criteria or 1 major plus 2 minor Jones criteria.
Major Jones criteria:
- polyarthritis (arthritis in two or more joints)
- erythema marginatum (skin rash)
- subcutaneous nodules
Minor Jones criteria:
- previous rheumatic fever or rheumatic heart disease
- laboratory findings including elevated erythrocyte sedimentation rate, elevated C-reactive protein, elevated white blood cell count
- prolonged PR interval on an electrocardiogram (EKG) (a pause in the electrical activity)
The Role of Polyarthritis in Rheumatic Fever
Symptoms of polyarthritis include painful, tender, swollen, warm joints and usually occur early in the course of rheumatic fever. The most commonly affected joints associated with polyarthritis related to rheumatic fever are:
Vertebral joints are not usually affected but the following joints may be affected:
Joint pain and fever associated with rheumatic fever usually subside within 2 weeks. The laboratory value of the erythrocyte sedimentation rate usually returns to normal within 3 months if carditis does not persist.
Arthralgia associated with rheumatic fever differs from arthralgia associated with rheumatoid arthritis by the absence of tenderness during passive movement of the affected joint (person performing examination moves patient's joint through range of motion).
Resolving Rheumatic Fever
The acute phase of rheumatic fever lasts only 6 weeks in 75% of cases. Symptoms improve in 90% of rheumatic fever cases within 12 weeks. Symptoms of rheumatic fever continue for 6 months or more in less than 5% of patients.
Rheumatic Fever, www.emedicine.com/ped/topic2006.htm, eMedicine.
Rheumatic Fever, www.merck.com/mrkshared/mmanual/section19/chapter270/270a.jsp, Merck Manual.
Rheumatic Fever, www.mayoclinic.com/health/rheumatic-fever/DS00250/DSECTION=1, Mayo Clinic.