In addition to sore throat and fever, some patients exhibit the stigmata of scarlet fever: circumoral pallor, strawberry tongue, and a fine diffuse erythematous macular-papular rash that has the feeling of goose flesh. The tongue initially has a white coating, but red and edematous lingual papillae later project through this coating, producing a white strawberry tongue. When the white coating peels off, the resulting red strawberry tongue is beefy red with prominent papillae. Patients infected with A. haemoyticum may present with similar findings.
Compared with classic streptococcal pharyngitis, the onset of viral pharyngitis is typically more gradual, and symptoms more often include rhinorrhea, cough, and diarrhea. Many upper respiratory tract infections present with symptoms of rhinorrhea and nasal obstruction, whereas systemic symptoms and signs, such as myalgia and fever, are absent or mild.
Gingivostomatitis is characteristic of herpes simplex virus-1 (see Chapter 65). Herpangina is an enteroviral infection with sudden onset of high fever, vomiting, headache, malaise, myalgia, backache, conjunctivitis, poor intake, drooling, sore throat,and dysphagia. The oral lesions of herpangina may be nonspecific, but classically there are one or more small, tender, papular,or pinpoint vesicular lesions on an erythematous base scatteredover the soft palate, uvula, and tongue. These vesicles enlargefrom 1 to 2 mm to 3 to 4 mm over 3 to 4 days, rupture, and produce small, punched-out ulcers that persist for several days.
The principal challenge is to distinguish pharyngitis caused by group A streptococcus from pharyngitis caused by nonstreptococcal (usually viral) organisms. A rapid streptococcal antigen test, a throat culture, or both are often performed to improve diagnostic precision and to identify children most likely to benefit from antibiotic therapy of streptococcal disease.
Many rapid diagnostic techniques for streptococcal pharyngitis are available with excellent specificity of 95% to 99%. The sensitivity of these rapid tests varies, however, and negative rapid tests should be confirmed by a throat culture.
Throat culture is the diagnostic gold standard for establishing the presence of streptococcal pharyngitis. False-positive cultures can occur if other organisms are incorrectly identified as group A streptococcus. As many as 20% of positive cultures in children during winter months reflect streptococcal carriers and not acute pharyngitis.
The predictive values of white blood cell count and differential, erythrocyte sedimentation rate, and C-reactive protein arenot sufficient to distinguish streptococcal from nonstreptococcal pharyngitis, and these tests are not routinely recommended.The white blood cell count in patients with infectious mononucleosis usually shows a predominance of atypical lymphocytes.
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The differential diagnosis of infectious pharyngitis includes other local infections of the oral cavity, retropharyngeal abscesses (S. aureus, streptococci, anaerobes), diphtheria (if unimmunized), peritonsillar abscesses (with quinsy sore throat or unilateral tonsil swelling caused by streptococci, anaerobes, or, rarely, S. aureus), and epiglottitis. In addition neutropenic mucositis (leukemia, aplastic anemia), thrush (candidiasis secondary to T-cell immune deficiency), autoimmune ulceration (systemic lupus erythematosus, Behçet disease), and Kawasaki disease may cause pharyngitis. Pharyngitis is often a prominent feature of Epstein-Barr virus-associated mononucleosis (see Chapter 99).