Diphtheria overview

# Overview
Diphtheria (Greek  (diphthera)  pair of leather scrolls) is an upper respiratory tract illness characterized by sore throat, low-grade fever, and an adherent membrane (a pseudomembrane) on the tonsils, pharynx, and/or nasal cavity. A milder form of diphtheria can be restricted to the skin. It is caused by Corynebacterium diphtheriae, a facultatively anaerobic gram-positive bacterium.
Diphtheria is a highly contagious disease that is spread via direct physical contact or breathing the aerosolized secretions of infected individuals. Once quite common, diphtheria has largely been eradicated in developed nations through widespread vaccination. In the United States, for instance, there were only 57 reported cases of diphtheria between 1980 and 2004 (and only five cases since 2000), as the DPT(DiphtheriaPertussisTetanus) vaccine is given to all schoolchildren. Boosters of the vaccine are recommended for adults, since the benefits of vaccination decrease with age; they are particularly highly recommended for those traveling to areas where the disease has not yet been eradicated.

# Historical perspective
Before 1826, diphtheria was known by different names across the world. In 1826, the term "diphtheria" was introduced by French physician Pierre Bretonneau. The name alludes to the leathery, sheath-like membrane that grows on the tonsils, throat, and in the nose in patients with the disease.

# Classification
Diphtheria can be classified according to the type of Corynebacterium that causes a specific case. It can also be classified according to the resulting clinical presentation into respiratory, systemic, or cutaneous diphtheria.

# Causes
C. diphtheriae is a facultatively anaerobic, gram positive organism that is characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods with a length of 1 to 8 m and width of 0.3 to 0.8 m. These rods form ramified aggregations in culture that have been described as looking like "Chinese characters." The bacterium may contain polymetaphosphate aggregates called Volutin granules. It is only pathogenic in humans.

# Differential diagnosis
Respiratory diphtheria must be differentiated from respiratory tract or other infections that present with fever, neck swelling, cough, and/or pharyngeal exudates. Cutaneous diphtheria must be differentiated from other bacterial and fungal causes of skin ulceration.

# Epidemiology and Demographics
Diphtheria is observed worldwide, though it is rare in the United States due to widespread vaccination. Diphtheria is a significant cause of illness and death in developing countries, where vaccination coverage tends to be lower.

# Risk factors
Common risk factors in the development of diphtheria include lack of immunization, history of travel to areas endemic for diphtheria, exposure to overcrowding and/or poor sanitary conditions, and immunocompromised status.

# Screening
There are no screening recommendations for diphtheria.

# Natural History, Complications, and Prognosis
Diphtheria is a vaccine-preventable disease that can lead to such severe complications as respiratory failure, myocarditis, polyneuropathies, and death. The overall case-fatality rate for diphtheria is 510%, with higher death rates (up to 20%) among patients younger than 5 or older than 40 years of age.

# Diagnosis

## History and Symptoms
Respiratory diphtheria presents with a wide range of systemic and respiratory symptoms. Cutaneous diphtheria usually presents with ulcers or pustular lesions, which can involve various different parts of the body. Lesions may be covered by a grayish-white pseudomembrane, similar to tonsillar exudates of respiratory diphtheria.

## Physical Examination
A patient with diptheria usually looks ill; systemic signs such as fever, tachypnea, and tachycardia are common. Pharyngeal, respiratory, neurologic, cardiac, and other physical examination findings depend upon the extent and severity of the infection.

## Laboratory Findings
A presumptive diagnosis of diphtheria is usually based on clinical features. A definitive diagnosis is made by growing the specific Corynebacterium species on special cultures from the respiratory tract secretions or cutaneous lesions.
Culture of the lesion is performed to confirm the diagnosis. It is critical to take a swab of the pharyngeal area, especially any discolored areas, ulcerations, and tonsillar crypts. Culture medium containing tellurite is preferred.
PCR assays can also be performed on isolates, swabs, or membrane specimens to rapidly confirm the presence of the tox gene responsible for the production of diphtheria toxin.

## X ray
Diphtheric myocarditis may result in systolic ventricular heart failure, which is evident by cardiomegaly on chest x-ray (CXR). Diphtheric patients may also present with bronchopneumonia. In this case, CXR may be normal, or it may show increased pulmonary vascular markings and/or inflammatory infiltrates. 

## CT
In cases of respiratory diphtheria, a CT scan may reveal swelling of the soft tissue of the nasopharynx, oropharynx, larynx uvula, and soft palate.

## MRI
An MRI may be performed to document diphtheric neuropathy.

## Electrocardiogram
An ECG in patients with diphtheria may be normal. However, in patients with diphtheria myocarditis, a wide range of abnormalities related to conduction and rhythm may be observed.

## Echocardiography
Echocardiography may be performed to document ejection fraction (EF) and any signs of ventricular systolic dysfunction if diphtheria infection has been complicated by systemic involvement of the myocardium.

## Other Imaging Findings
There are no other imaging findings in cases of diphtheria.

## Other Diagnostic Studies
There are no other diagnostic studies for diphtheria.

# Treatment

## Medical Therapy
The treatment of diphtheria consists of administering the diphtheria antitoxin (if the disease is identified early), administering the proper antibiotic therapy, and identifying individuals in close contact with the patient so as to provide them with the appropriate prophylaxis.

## Surgical Therapy
There is no role for surgery in the management of diphtheria.

## Primary prevention
The best way to prevent diphtheria is to get vaccinated. In the United States, there are four vaccines used to prevent diphtheria: DTaP, Tdap, DT, and Td. Each of these vaccines prevents diphtheria and tetanus.
The current childhood immunization schedule for diphtheria includes five doses of DTaP for children younger than seven years old. Preteens get a booster dose of Tdap at 11 or 12 years old, and teens who did not get Tdap when they were 11 or 12 years old should get a dose the next time they see their doctor. Adults should get a dose of Td every 10 years, according to the adult immunization schedule.

## Secondary prevention
There are no established guidelines for the secondary prevention of diphtheria. However, early diagnosis and prompt and adequate treatment with the appropriate antibiotic therapy and diphtheria antitoxin, good nursing care, and adequate airway management may help reduce the progression of the disease and prevent complications in affected individuals.