Measles in children

Clinical presentation and rash features

Measles differs from other childhood infections by its pronounced cyclic course. Each period of the disease is characterized by its own diagnostically significant symptoms.

At the onset of the disease, intoxication and catarrhal syndrome come to the forefront. Fever in measles is always higher and more prolonged than in many other exanthems. Catarrhal manifestations include pronounced rhinitis, conjunctivitis, and dry cough. An absolute pathognomonic sign of the infection is the appearance of specific elements on the mucous membrane — Koplik spots.

Characteristics of measles exanthem:

• The rash is large, maculopapular, and very abundant.
• The elements tend to coalesce with one another.
• The background of the skin remains unchanged.
• There is a strict sequential pattern in both the spread and fading of the rash.
• The process concludes with characteristic skin desquamation and pigmentation.

Differential diagnosis with rubella

The greatest difficulties often arise in differential diagnosis between measles and rubella. Unlike measles, rubella manifests immediately with the appearance of a rash, while catarrhal signs are absent or extremely mild.

The rash in rubella spreads rapidly — within a few hours it covers the trunk and extremities without the strict staging characteristic of measles. Intoxication in the initial period of rubella is moderate, accompanied by enlargement of the occipital and cervical lymph nodes. During the peak period, lymphadenopathy persists and exanthem appears, but the intoxication syndrome does not increase.

A special diagnostic algorithm for suspected rubella requires a thorough collection of epidemiological history (contacts within the incubation period, vaccination status) and the formulation of a detailed diagnosis indicating the form and severity.

Distinctions from infectious mononucleosis and scarlet fever

Differential diagnosis with infectious mononucleosis is performed during the period of maculopapular rash appearance. Specific signs of mononucleosis not characteristic of measles:

• Prolonged irregular fever.
• Tonsillitis (ranging from catarrhal to necrotic).
• Polylymphadenopathy with predominant involvement of the cervical group.
• Hepatosplenomegaly syndrome.
• Hemogram: moderate leukocytosis, lymphocytosis, and the appearance of atypical mononuclear cells.
• Absence of clear cyclicity and staging of the rash.
• Frequent appearance of a rash after administration of semisynthetic penicillins ("ampicillin rash").

When differentiating from scarlet fever, the character of the rash and the presence of tonsillitis are taken into account. It is important to remember that a throat swab for group A beta-hemolytic streptococcus is not absolute confirmation of scarlet fever due to possible asymptomatic carriage. However, taking a swab is strictly necessary to rule out pharyngeal diphtheria, and a hemogram must additionally be performed.

Allergic reactions and other exanthems

Measles must be differentiated from toxic-allergic reactions. Allergic exanthem is characterized by the absence of cyclicity, staging, and Koplik spots. There is a history of contact with an allergen, clinical skin pruritus is pronounced, and the prescription of desensitizing therapy yields a rapid and marked effect.

The differential diagnosis also includes:

• Enteroviral infection: distinguished by pronounced polymorphism of the rash.
• Kawasaki disease: acts as an exanthematous "mask". Prolonged fever in infants and young children is a "red flag" requiring mandatory inclusion of the syndrome in the diagnostic search.
• Roseola infantum (HHV-6): the rash appears only after a critical drop in temperature (3–5 days of fever), which is often mistaken for antibiotic allergy.

Effect of measles on tuberculin skin testing

An important clinical nuance: measles belongs to acute infectious processes that temporarily suppress cellular immunity.

Against the background of a prior infection, secondary anergy may develop in a child — a complete lack of response to tuberculin. This leads to false-negative Mantoux test results, which occur in 7–10% of infected or tuberculosis-sick children. This fact must be taken into account when planning tuberculin testing in convalescents.

Class and exam questions

What else to study on this topic

• Differential diagnosis of rubella and parvovirus B19 infection
• Congenital rubella syndrome (CRS) and teratogenic risks
• Roseola infantum (HHV-6) and common diagnostic errors
• Chickenpox and Herpes zoster: epidemiological connection
• Kawasaki disease as an exanthematous "mask" in early childhood

Other topics in the "Additional Topics" section

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