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Cutaneous diphtheria

Author: Dr Jenny Caesar, Dermatology Registrar, Glamorgan House, University Hospital of Wales, Cardiff, Wales, UK. DermNet NZ Editor in Chief: Adjunct A/Prof. Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. June 2020.


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What is cutaneous diphtheria?

Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae, a gram-positive bacillus. It generally affects the respiratory system and can also affect the skin. It can be prevented by vaccination and is very rare in countries with an immunisation programme.

Cutaneous diphtheria presents as a slow-healing ulcer.

Corynebacterium diphtheriae

Who gets cutaneous diphtheria?

Cutaneous diphtheria typically occurs in tropical areas where C. diphtheria is endemic, including in:

  • Asia
  • Africa
  • The South Pacific
  • The Middle East
  • The Caribbean.

In developed countries, cutaneous diphtheria most commonly presents after travel to an endemic area in a pre-existing skin condition or wound. It usually affects unvaccinated individuals.

Outbreaks of cutaneous diphtheria have also been reported in disadvantaged communities living in overcrowded conditions with poor access to sanitary facilities and healthcare.

Transmission of cutaneous diphtheria is thought to occur via direct person-to-person contact with the infected skin and contaminated dressings.

Cutaneous diphtheria has also been reported after traditional tattooing [1].

What causes cutaneous diphtheria?

Cutaneous diphtheria is caused by bacterial infection with Corynebacterium diphtheriae and less commonly, Corynebacterium ulcerans.

C. diphtheriae is a gram positive, non-encapsulated bacillus [2]. Both toxigenic and non-toxigenic strains have been implicated in cutaneous infection.

What are the clinical features of diphtheria?

Toxigenic strains of C. diphtheriae cause systemic toxicity.

Respiratory disease due to diphtheria characteristically presents as a thick, grey coloured membrane within the pharynx. Diphtheria can cause a sore throat, cervical lymphadenopathy, and progressive respiratory distress. Concurrent respiratory and skin infection are rare.

Cutaneous diphtheria

Cutaneous diphtheria is classically described as a well-circumscribed, non-healing ulcer with a ‘punched out’ appearance and covered by a grey membrane [1].

Lesions may start as a collection of vesicles which rapidly coalesce to form a clearly defined ulcer. They can be itchy, painful, and leak blood-stained exudate [2].

Localised injury to the skin often precedes infection, for example, a graze or insect bite [2]. Cutaneous diphtheria has also been identified after colonisation and infection of an existing skin condition [3,4].

Cutaneous diphtheria can be non-specific, and may be challenging to distinguish from skin infection caused by another pathogen [1,4].

What are the complications of cutaneous diphtheria?

Unlike respiratory diphtheria, in which there is a slow immune response that may not lead to subsequent immunity, cutaneous diphtheria typically results in a rapid antibody response. This means that individuals with skin infection are unlikely to develop concurrent pharyngeal diphtheria.

Systemic toxicity from cutaneous diphtheria due to toxigenic strains of the bacteria is rare, only occurring in 1–2% of cases.

Possible systemic complications linked to toxigenic diphtheria include:

  • Myocarditis
  • Neurological toxicity
  • Osteomyelitis
  • Septic arthritis.

Infected skin can be a reservoir for passing the infection onto others, particularly in areas where herd immunity is low due to suboptimal immunisation.

How is cutaneous diphtheria diagnosed?

The diagnosis of cutaneous diphtheria should be considered in a non-immunised individual with a non-healing ulcer and recent travel to an endemic area.

C. diphtheriae may be cultured from a bacterial wound swab.

As laboratory processing for diphtheria may not be routine, it is vital that complete clinical information is provided to alert the laboratory to consider culture for atypical organisms [1].

What is the differential diagnosis for cutaneous diphtheria?

The differential diagnosis for cutaneous diphtheria includes:

  • Pyoderma gangrenosum — a rapidly enlarging, painful ulcer with an undermined edge
  • Cutaneous leishmaniasis — a parasitic infection transmitted by sandflies infected with the protozoa Leishmania
  • Tropical ulcer — a rapidly enlarging painful ulcer with purple edges and a necrotic centre
  • Yaws — a chronic tropical skin infection caused by Treponema pallidum pertenue
  • Chancroid — one or more painful ulcers caused by Haemophilus ducreyi.

What is the treatment for cutaneous diphtheria?

Cutaneous diphtheria infection needs to be identified and treated to prevent spread of disease [4]. Treatment includes:

  • Antibiotics, such as erythromycin (40 mg/kg/day; maximum, 2 g/day) for 14 days
  • An antitoxin to neutralise toxigenic systemic effects may be considered for membranous ulcers greater than 2 cm2 and in patients with systemic toxigenic symptoms [6]
  • Isolation to reduce the spread of disease.

Cases are no longer thought to be contagious after 48 hours treatment with antibiotics.

Diphtheria is a notifiable disease in New Zealand and public health advice should be sought. Contact tracing is advised for all close contacts. Nasal, pharyngeal, and skin swabs should be obtained from any wound sites. Contacts may require prophylaxis with erythromycin 500 mg QDS for 7–10 days.

Vaccination is essential to promote herd immunity and to reduce the risk of transmission of diphtheria. In New Zealand, vaccination against diphtheria is part of the National Immunisation Schedule and is given concurrently with tetanus and pertussis and sometimes also with polio, hepatitis B, and Haemophilus influenzae type b.

What is the outcome for cutaneous diphtheria?

The prognosis for uncomplicated cutaneous diphtheria is good, with most cases responding to oral antibiotics and simple wound care measures.

Mortality is reported at 5–10% in systemic toxigenic diphtheria [7].

To prevent re-infection, individuals and close contacts should ensure their vaccination status is up to date.

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References

  1. Sears A, McLean M, Hingston D, Eddie B, Short P, Jones M. Cases of cutaneous diphtheria in New Zealand: implications for surveillance and management. NZMJ 2012; 125: 64–71. Journal
  2. Anzar S, Watkis V, Saleh H, Sharma P, Bandi S. PO-0176 A Case of Cutaneous Diphtheria. Archive of Disease in Childhood 2014; 99: A304–5. Journal
  3. Höffler W. Cutaneous Diphtheria. Int J Dermatol 1991; 301: 845–7. doi: 10.1111/j.1365-4362.1991.tb04348.x. PubMed
  4. Barroso L, Pegram P. Diphtheria. UptoDate 2018. Available at: www.uptodate.com/home (accessed on 24 February 2020)
  5. Abuhammour W, Alhamdani S, Yousef N. Diphtheria. BMJ Best Practice 2019. Journal
  6. Public Health England. Diphtheria: the green book. 2013. Available at: www.gov.uk/government/publications/diphtheria-the-green-book-chapter-15 (accessed on 23 February 2020)
  7. World Health Organisation. Diphtheria. Updated 2018. Available at: www.who.int/immunization/diseases/diphtheria/en/ (accessed on 23 February 2020)

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