Diphtheria

Clinical presentation and organ involvement

The infection manifests with local and general symptoms. At the portal of entry (mucous membranes of the oropharynx, respiratory tract, nose, less commonly skin or genitalia), fibrinous-necrotic inflammation develops. A characteristic dirty-gray deposit forms, which is tightly adhered to the underlying tissues.

General manifestations are caused by a powerful intoxication syndrome. In severe cases, the toxin affects target organs:

• Heart: acute myocarditis, muffled heart sounds, arrhythmias, atrioventricular block.
• Kidneys: development of acute nephrosis and renal failure.
• Nervous system: polyneuritis, early cranial nerve neuritis (IX-X pairs).
• Adrenal glands.

Involvement of the lymphatic system is also characteristic: regional lymphadenitis and serous-hemorrhagic periadenitis occur. When formulating a detailed diagnosis, the physician must indicate the localization, etiological confirmation, and severity grade (assessed by the prevalence of the process, signs of toxicosis, and presence of complications).

Dangerous complications

The severity of the disease directly determines the risk of early and late complications. The most formidable conditions require emergency treatment in an intensive care unit (ICU):

• True croup (laryngeal stenosis): edema of the epiglottic mucosa and vocal cords combined with deposits leads to narrowing of the glottis. This causes acute respiratory failure. If there is a threat of immediate complete airway obstruction by a sloughing deposit, emergency tracheotomy is indicated.
• Infectious-toxic shock (ITS) and hemorrhagic syndrome.
• Multiple organ dysfunction syndrome (MODS) and encephalopathy (presumably of metabolic genesis).

Diagnostics and differential search

The diagnosis is established based on a combination of clinical and epidemiological data and confirmed by laboratory tests.

1. Specific diagnostics: bacteriological examination of nasopharyngeal and oropharyngeal swabs (if necessary, from a wound surface or genitalia) for the presence of Corynebacterium diphtheriae.
2. Instrumental methods: laryngoscopy (reveals edema of the epiglottis and cords, presence of deposits), chest radiography, and potentially bronchoscopy.
3. Laboratory monitoring: monitoring of blood gas composition, acid-base balance (ABB), electrolytes, creatinine, urea, and hemogram.

Thorough differential diagnosis is mandatory. Prior to laryngoscopy, laryngeal diphtheria is differentiated from parainfluenza, exacerbation of chronic laryngitis, and oncological processes of the larynx and mediastinum. Tonsillar involvement with necrosis and pronounced asymmetric lymph node enlargement requires the exclusion of tularemia. The latter would be supported by a negative diphtheria swab, formation of a bubo without skin hyperemia, and an epidemiological history (contact with farm animals, consumption of raw milk).

Principles of treatment

The basis of successful treatment in the initial period and at the height of the disease (prior to the rejection of deposits) is emergency specific therapy.

• Specific detoxification: intramuscular administration of equine antitoxic diphtheria serum (ADS). The dose (from 15,000 to 150,000 IU and higher) and frequency of administration strictly depend on the localization, prevalence, and severity of the process. Fresh frozen donor plasma and immune gamma globulin are also used.
• Antibacterial therapy: broad-spectrum drugs (semisynthetic penicillins, cephalosporins, fluoroquinolones).
• Pathogenetic therapy: nonspecific detoxification to correct metabolic disorders, anti-shock measures. To improve airway patency and relieve edema, the use of corticosteroids and antihistamines is advisable.
• Regimen: strict bed rest and a special diet. Following the alleviation of acute conditions, convalescent rehabilitation is carried out.

Class and exam questions

What else to study on this topic

• Criteria for assessing the severity grade of toxic oropharyngeal diphtheria.
• Stages of development of localized croup in respiratory diphtheria.
• Early and late complications: onset timing and pathogenesis.
• Differential diagnosis of oropharyngeal diphtheria and the tonsillar-bubo form of tularemia.
• Rules and strict indications for the administration of equine antitoxic serum.

Other topics in the "Respiratory Infections" section

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