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Common Skin Infections

Measles 

Prodromal symptoms are respiratory and usually consist of fever, malaise, rhinitis, conjunctivitis and cough. The patient is highly infectious at this stage. Koplik’s spots may appear on the buccal mucosa inside the cheek and mouth; these tend to fade as the rash begins. The main illness consists of fever and a dusky red maculopapular rash which starts on the forehead and behind the ears and spreads to the rest of the body. It fades to a brownish colour and resolves with fine desquamation. It is not itchy. Generally, the fever, conjunctivitis and respiratory symptoms subside when the rash is at its peak.

The incubation period is approximately 10 days, the prodrome lasts 2-4 days and the rash appears approximately 2 weeks post exposure. Spread is via the respiratory route. Patients are infectious from the beginning of the prodrome until four days after the appearance of the rash. The incidence increases in winter and early spring.

 Kopliks spots in buccal mucosa

Complications of measles

  • Opportunistic infections can occur, particularly bronchopneumonia, croup and otitis media.
  • Giant cell pneumonia: rare, usually only in immunodeficient or with chronic debilitating disease. It is caused directly by measles virus and is very severe.
  • Measles inclusion body encephalitis: only in immunosuppressed, presents with convulsions, myoclonic jerks, coma and stupor. Death occurs within weeks or months; the course is more rapid than subacute sclerosing panencephalitis (SSPE).
  • Acute measles postinfectious encephalitis: occurs in 1 in 1000-5000 cases of acute measles and 20-40% have lasting neurological sequelae such as fits, hemiplegia and mental retardation. It develops with fever, headache, seizures, cerebellar ataxia and coma. The mortality rate is 15%.
  • Subacute sclerosing panencephalitis (SSPE): usually occurs in children and young adults 6-8 years after acute measles and has an incidence 1 per million cases. It is commonest in children who had measles before the age of 2 years. The illness lasts 1­3 years and leads to death. It is characterised by generalised intellectual and psychological deterioration, fits, aphasia, myoclonic jerks and chorioretinitis. There are characteristic EEG changes. It is due to persistent measles infection and patients have high titres of anti-measles IgG and IgM in serum and CSF.
  • Other complications include hepatitis, myocarditis, pericarditis and mesenteric lymphadenitis. 
  • Case fatality rates for measles are age related- high under the age of 1year, lowest for the age group 1-9 years, then increasing with age.

A saliva sample should be sent for specific measles IgM, ideally 3 days after the onset of the rash. A blood sample may be sent at the time of diagnosis, for the detection of measles specific IgM, followed by a further sample 7-10 days later to detect a rise in antibody titre.

Contact with measles poses a risk for children under the age of 1 year, the immunocompromised, and those with chronic debilitating disease. Parents who do not remember either having measles or being vaccinated are also at risk. It is therefore of importance that these individuals be immunised. Susceptible individuals at risk may be protected after exposure by the administration of human normal immunoglobulin, given within 3 days of exposure. Effectiveness disappears if given greater than 6 days after exposure.

The illness is normally self-limiting, but complications such as bacterial infection will need to be treated with antibiotics. More severe complications will obviously necessitate referral to hospital.

 

Roseola infantum

Caused by Human Herpes Virus 6 (HHV6)

Primary HHV6 infection usually manifests in children as an acute febrile illness lasting 3-4 days; 10% will also have a macular or papular rash on the face and trunk similar to measles or rubella (it is commonly misdiagnosed). Transmission is via salivary secretions. Complications include febrile seizures, hepatitis, bone marrow suppression, encephalitis, gastrointestinal symptoms and respiratory symptoms (pneumonitis in 10%). HHV6 infection accounts for a third of febrile seizures under the age of 3 years.

The diagnosis is generally clinical, but in some circumstances (e.g. child with neurological complications) indirect immunofluoresence and PCR can be used to identify the virus. These investigations are generally done by a reference lab and need to be discussed in advance.