Differentials
Streptococcus pyogenes pharyngitis
SIGNS / SYMPTOMS
Rapid onset with prominent sore throat and fever.
Headache and gastrointestinal symptoms are frequent.
Red throat and enlarged tonsils covered by yellow or blood-tinged exudate.
Enlarged and tender cervical lymphadenopathy.
Some patients have a fine papular rash with circumoral pallor and strawberry tongue (scarlet fever).[47]
INVESTIGATIONS
Positive throat culture is the definitive test for Streptococcus pyogenes diagnosis.
Rapid antigen detection tests can confirm the presence of group A streptococci carbohydrate antigen on a throat swab within minutes. However, the sensitivity of these tests is between 70% and 90% compared with blood agar plate culture.
Acute epiglottitis
SIGNS / SYMPTOMS
Acute fulminating course of high fever, sore throat, and rapidly progressing respiratory obstruction.
Drooling is usually present, and patient maintains hyperextended neck in attempt to maintain open airways.[48]
INVESTIGATIONS
Direct visualisation of the epiglottis shows cherry-red swollen area.
A lateral x-ray of soft tissue of the neck shows enlarged epiglottitis protruding from the anterior wall of the hypopharynx (thumb sign).
Usually caused by Haemophilus influenzae b which, like diphtheria, should be vaccine-preventable.
Infectious mononucleosis
SIGNS / SYMPTOMS
Prominent tonsillar enlargement with exudate and cervical lymphadenopathy.
Hepatomegaly and splenomegaly usually present.
Rash and generalised fatigue occur as part of infectious mononucleosis syndrome.[49]
INVESTIGATIONS
Positive heterophil antibody test or positive serological test for Epstein-Barr virus.
Infectious mononucleosis type illnesses can also be caused by cytomegalovirus, toxoplasmosis, HIV seroconversion, and some other pathogens.
Acute necrotising ulcerative gingivitis (Vincent's angina)
SIGNS / SYMPTOMS
Periodontal disease associated with spirochaetes and fusobacteria.
Necrosis and ulceration of the gingiva between the teeth, with adherent greyish pseudomembrane covering the gingiva.
Fever, malaise, and lymphadenopathy.
INVESTIGATIONS
Dark-field microscopy of debris from the pseudomembrane shows spirochaetes.
Staphylococcal or streptococcal impetigo
SIGNS / SYMPTOMS
Typically affects the skin of the face or extremities that have been traumatised.
Tiny vesicles or pustules form initially and develop into small blisters that rupture, forming a honey-coloured, crusted plaque.
Little or no pain. No surrounding erythema, and constitutional symptoms are generally absent.
INVESTIGATIONS
Bacteriological culture or microscopy shows staphylococci or streptococci.
Mumps
SIGNS / SYMPTOMS
Most recognisable by painful bilateral parotid swelling without sore throat or exudate/pseudomembrane.
Often clinically distinguishable from diphtheria, but facial and neck swelling can look similar and the incidence of both conditions is increased in populations with low vaccine coverage.
INVESTIGATIONS
Diagnosis (and discrimination from diphtheria) is often clinical, but polymerase chain reaction (PCR) of buccal swabs and serology (IgM) detection can provide laboratory confirmation.
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