Common Skin Infections

Other main causative agents of a maculopapular rash

Both Epstein-Barr virus (EBV) and Cytomegalovirus (CMV) can cause infectious mononucleosis. The seropositivity of EBV increases with age, with greater than 90% of adults worldwide being seropositive: conversely, primary EBV is unusual in the middle aged and elderly. There are two age groups in whom infection peaks; 1-6 years and 14-20 years.

EBV infection 

It may be subclinical in healthy adults (50% infections) or present abruptly with a painful throat, fever, malaise, headaches, neck stiffness, anorexia and vague abdominal discomfort. Palatal petechiae occur in the first week of illness, and they may be associated with a greyish membrane and exudative tonsillitis. Two types of rashes are seen; a generalised, faint, non-itchy morbilliform rash lasting under 2 days, and a florid maculopapular rash seen in patients given penicillin. Generalised lymphadenopathy occurs, the nodes being palpable for several weeks. Splenic enlargement occurs in 50% patients and hepatomegaly, mild jaundice and derangement of liver function also occurs in a significant proportion of cases.

Close contact: the virus is present in salivary secretions. The incubation period is 30-50 days.

  Complications

• Pharyngeal oedema and tonsillar enlargement can result in obstruction of the pharynx or trachea.
• Splenic rupture is very rare. 
• Neurological complications such as meningitis, encephalitis or Guillain-Barre syndrome may precede, accompany or post-date Infectious mononucleosis by weeks.
• Hepatic complications: jaundice occurs in 5-10%.
• Chronic cases can occur where symptoms persist for greater than 1 year (approx 1 in 2000) cases. The average duration of symptoms is 2-3 weeks.
• Immunological complications include haemolytic or aplastic anaemia, thrombocytopaenia, agranulocytosis and hypogammaglobulinaemia.

Clinical Tip: Affected individuals should be warned to avoid contact sports for at least 6 months following infection if their LFTS are abnormal due to the risk of splenic rupture if kicked etc.

Diagnosis is made by full history and in the interpretation of any investigations

• Blood film: the presence of atypical lymphocytes is highly suggestive, although they are also seen in CMV infection, hepatitis B, influenza B and rubella.
• Monospot: detects IgM heterophile antibodies which cause haemagglutination of erythrocytes from species other than humans (sheep are usually used).
• EBV VCA IgM (viral capsid antigen): demonstration of IgM antibodies is diagnostic of recent infection. Demonstration of IgG antibodies is not usually helpful as they are usually present in the first serum sample taken after diagnosis.

Treatment is supportive; analgesia for the painful throat and paracetamol for fevers. Obviously penicillin should be avoided.

Pityriasis Rosea and HHV6/HHV7

There is increasing evidence that Pityriasis Rosea is associated with HHV6 and 7 infection. It most commonly affects ages 15-30 and starts with the typical 'herald patch' usually the trunk. The hallmark is the erythematous macule with peripheral collarette scale which follows on the trunk, often following the lines of the ribs (the so-called Christmas Tree distribution). This is best seen if you stand a little way back from the patient and observe the back of the chest from a slight distance. Rash may be a little itchy but usually asymptomatic. My old boss used to tell me it lasted Forty days and Forty nights!! 

It doesn't usually need treatment although a mid strength topical steroid may relieve lesions and very rarely I prescribe narrow band UVB for protracted cases. Occasionally an inverse pattern can occur.

Clinical Tip: Look for Christmas Tree pattern and be aware that secondary syphilis may mimic Pityriasis rosea.

Pityriasis rosea- note typical Herald Patch and Christmas tree distribution following ribs

Cytomegalovirus (CMV)

Clinical presentation is similar to above but the majority of cases in otherwise healthy adults are asymptomatic.

Incubation is 4-8 weeks for a primary infection. Transmission can occur via saliva, sexually (particularly homosexual men) and more rarely from blood transfusion or organ transplantation. It is also transmitted perinatally via swallowed genital secretions and breast milk, and can occur as a congenital infection.

Primary CMV infection in the first 28 weeks of pregnancy causes a risk of cytomegalic inclusion disease in the foetus of about 4%. However, the presence of intrauterine infection does not necessarily cause clinically evident disease in the infant, the majority of these infants developing normally. These cases are difficult and should be discussed with the virologist and obstetrician. Ultrasound scanning and amniotic fluid testing for CMV may help identify potentially damaged cases. In the case of pregnant healthcare workers exposed to infectious CMV cases there is little evidence that they have an increased risk of developing infection, but good hygienic measures should be advised.

Symptomatic infants are described as having the syndrome of ‘cytomegalic inclusion disease’ which includes intrauterine growth retardation, jaundice, hepatosplenomegaly, thrombocytopenia, encephalitis, microcephaly, pneumonitis, myocarditis, hepatitis and congenital abnormalities of the 1^st branchial arch and anophthalmia. Of those infected, 7% will be symptomatic at birth and 1% will die in infancy. Those which survive suffer fits, spastic diplegia, perceptual organ damage such as optic atrophy and deafness, and mental retardation. Of those infants which are asymptomatic at birth 15% will have hearing defects and/or mental retardation. Congenitally infected infants excrete CMV in urine, saliva and nasal secretions and so care should be taken to avoid close contact with pregnant women.

Diagnosis

The virus can be isolated from urine samples and saliva soaked into a cotton tipped swab sent in viral transport medium. Virus can be more rapidly detected in urine using the DEAFF test. The presence of CMV IGM in an acute blood sample is diagnostic of recent infection. PCR of plasma, whole blood and lymphocytes can be used to diagnose systemic viraemia. This is useful in monitoring immunosuppressed patients on therapy.

Again, management is supportive. Antiviral therapy is only indicated for serious or life-threatening CMV infection in the immunocompromised.

• Coxsackie A and echovirus can cause a fine rubella-like rash. It may be associated with fever, malaise and cervical lymphadenopathy and recovery is usually uneventful.
• Dengue virus often causes a diffuse, discrete maculopapular rash, heralding the recovery phase of dengue fever.