Characteristics of diphtheritic plaque
A pathognomonic sign of diphtheria is a specific plaque. In the initial period, it appears as a gel-like mass that can be removed, but quickly reforms. By days 2–3, the classic plaque forms:
- Appearance: greyish-white, shiny, with a pearly sheen.
- Relationship to tissues: protrudes above the mucosa ("plus tissue"), firmly adhered to underlying structures.
- Attempted removal: accompanied by bleeding of the mucosa.
The physical properties of the removed film are unique: it does not dissolve and sinks in water, cannot be rubbed between microscope slides, and retains the shape of the surface on which it formed, like a cast.
Classification of forms by severity
Clinical forms of pharyngeal diphtheria range from mild to extremely severe (hypertoxic). The severity is determined by the rate of disease progression, area of plaque, extent of edema, and severity of intoxication.
Mild forms (localized and disseminated)
- Localized: plaques do not extend beyond the tonsils (insular and membranous forms). It presents with moderate intoxication (fever up to 38°C) and slight enlargement of submandibular lymph nodes.
- Disseminated: the plaque spreads to the palatine arches and uvula. This is an intermediate variant between mild and moderate severity.
Moderately severe and severe (toxic) forms
The main sign of transition to a toxic form is the appearance of oropharyngeal edema and cervical tissue edema.
- Subtoxic: pastosity of the subcutaneous tissue does not reach the middle of the neck.
- Toxic grade I: edema reaches the middle of the neck.
- Toxic grade II: edema descends to the base of the neck. Tonsils are enlarged to grade 2–3, plaques may become "corrugated".
- Toxic grade III: massive edema descends below the clavicles, the pharyngeal lumen is not visible, voice is muffled ("hot potato" voice). Intoxication is extremely severe.
Specific complications
Complications in diphtheria are caused by the action of the exotoxin and depend on the form of the disease.
- Infectious-toxic shock (ITS): develops in the first 24 hours in the hypertoxic form.
- Myocarditis: the most frequent complication. Early onset (from day 4) is severe; late-onset develops in the 3rd–4th week. Pre-clinical detection is performed using enzymes (CK, AST, LDH) and ultrasound.
- Polyradiculoneuropathies: begin with cranial nerve involvement (n. ciliaris, n. abducens, IX and X pairs), causing nasal speech, choking, accommodation paralysis, and strabismus. In severe cases, paresis acquires an ascending character, up to paralysis of the respiratory muscles.
- Toxic nephrosis: moderate proteinuria and cylindruria without changes in urine specific gravity and without hypertension.
Briefly: answers to topical questions
What microorganism is the causative agent of diphtheria, and what are its morphological properties?
The causative agent of diphtheria is Corynebacterium diphtheriae. It is a rod with rounded, thickened ends (due to volutin granules), resembling a club. It has the following properties:
- In culture, it exhibits marked polymorphism (coccoid, club-shaped, segmented, filamentous forms).
- Capable of forming L-forms and filterable forms.
- Does not form spores or true capsules.
- Non-motile.
- Fimbriae are present on the surface.
- Toxigenic strains have a microcapsule containing cord factor.
What is the clinical difference between the insular form of localized diphtheria and the membranous form?
The difference lies in the pattern of distribution of the fibrinous plaque on the tonsils.
| Form of localized diphtheria | Characteristics of the plaque |
|---|---|
| Membranous form | The plaque primarily occupies the surface facing the pharyngeal lumen. |
| Insular form | The plaque appears as separate areas across the entire surface of the tonsils. |
What is the vaccination and revaccination schedule for diphtheria according to the national immunization schedule?
According to the Russian National Immunization Schedule, vaccination and revaccination against diphtheria are carried out at the following intervals:
- 3–4–5 months: DTaP
- 18 months: DTaP
- 6 years: Td
- 11 years: Td
- 16–17 years: Td
- Adults: Td (or Td-M) once every 10 years.
Properties of the diphtheritic film: Dense, Sinks, Cannot be rubbed, Bleeds.
Class and exam questions
What is the main difference between the toxic form of diphtheria and the localized form?
The toxic form is necessarily accompanied by edema of the soft tissues of the oropharynx and subcutaneous fat of the neck, whereas in the localized form, plaques are strictly confined to the tonsils, and there is no neck edema.
What complete blood count changes are characteristic of toxic diphtheria?
Toxic forms are characterized by pronounced neutrophilic leukocytosis and elevated ESR. The more severe the form, the more striking the changes.
How fast does diphtheria antitoxin work?
Clinical signs of fibrinous plaque rejection appear 12–24 hours after the administration of antitoxic serum.
What else to study on this topic
- Features of the localized catarrhal form
- Hypertoxic form and hemorrhagic syndrome
- Respiratory diphtheria (croup): stages and differences from pharyngeal diphtheria
- Detailed analysis of the polyradiculoneuropathy stages in diphtheria
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