Infectious mononucleosis (glandular fever) – skin and mucosal signs

Definition

Infectious mononucleosis is an infection usually caused by Epstein-Barr virus (EBV, human herpesvirus 4), with fever, pharyngitis, lymphadenopathy and fatigue. Cytomegalovirus can also cause a similar picture.

Occurrence & epidemiology

It typically affects young adults aged 15–25 years, both sexes equally. Over 95% of adults are EBV-seropositive; in young children, primary infection is usually asymptomatic. Transmission is mainly via saliva, for example by kissing.

Clinical features

• Incubation period usually 6–7 weeks; fever, pharyngitis, cervical lymphadenopathy, splenomegaly (in about 50%), periorbital oedema.
• Enanthem: petechiae on the hard and soft palate in about 50% of young adults during the first days of illness.
• Exanthem: generalised maculopapular, usually faint and non-itchy, starting on the trunk and upper arms and spreading to the face and forearms; also morbilliform, scarlatiniform, vesicular or purpuric; resolves after about a week. Frequency without antibacterial drugs 4.2–13%, according to more recent data up to about 20%.
• After starting antibacterial drugs, a more intense, itchy maculopapular drug eruption may appear (including extensor surfaces, trunk, palms and soles); the previously reported frequency of up to 90% is now considered far too high.
• Less common: itchy jaundice with excoriations, immune thrombocytopenia, cold urticaria, erythema nodosum.

Diagnosis

• Heterophile antibodies (Monospot): positive in 85–90% of adolescents and adults, but only in about 50% of children aged 2–5 years; often still negative in the first week of illness.
• Blood count: lymphocytosis with atypical lymphocytes (up to 30% of white cells); transaminases often raised.
• EBV-specific serology: VCA IgM indicates primary infection; VCA IgG appears early and persists for life; EBNA IgG appears only after 2–4 months.

Differential diagnoses

• Measles
• Rubella (German measles)
• Urticaria
• Secondary syphilis (lues II)
• Scarlet fever
• Acanthosis nigricans maligna

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References (selection)

1. DermNet: Infectious mononucleosis
2. MSD Manual Professional: Infectious mononucleosis

Cross-references