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Scarlet Fever and Childhood Infections

Scarlatina

For medical students2 min readUpdated 2026-10-10

While classical scarlet fever is driven by erythrogenic toxin-producing Streptococcus pyogenes, understanding its morphology alongside other pediatric exanthems and infectious diseases (measles, mumps, infectious mononucleosis, and poliomyelitis) is essential for differential diagnosis in pathology.

Specific MarkerWarthin-Finkeldey giant cells in lymph nodes are a pathognomonic sign of measles infection
Pneumonia TypeMeasles pneumonia is interstitial, involving the interalveolar septa
Mononucleosis CellsAppearance of a high number of activated atypical T lymphocytes in the peripheral blood
Mumps ComplicationSevere orchitis can lead to testicular infarction and subsequent male infertility

Morphological Changes in Measles

Although the primary topic focuses on scarlet fever, studying viral infections like measles is critical for mastering pediatric pathology. Measles changes span multiple organ systems, creating a characteristic post-mortem and histological picture.

Skin lesions at the site of specific rashes show marked hyperemia of the microvasculature. Lymphocytic and histiocytic infiltrates form around blood vessels. Diapedetic hemorrhages occur, later leaving behind hemosiderin deposits. In the epidermis itself, cellular vacuolization and specific multinucleated giant epithelial cells are observed.

Lymphatic system reaction manifests as follicular hyperplasia in lymph nodes. The most critical diagnostic (pathognomonic) criterion is the presence of Warthin-Finkeldey multinucleated giant cells within the lymphoid tissue.

Respiratory tract changes begin with serous-catarrhal pharyngitis and tracheitis. As the process progresses, inflammation extends downward into the bronchial tree and alveoli. Specific measles pneumonia is interstitial: the inflammatory process localizes to the interalveolar septa and peribronchial tissue. The bronchial mucosal epithelium undergoes squamous cell metaplasia. Microscopically, the alveoli contain macrophage-lymphocytic infiltrates, hyaline membranes, and giant cells. If secondary bacterial flora supervenes, severe purulent-necrotic bronchitis develops.

Complications and Outcomes of Measles

Complications may be triggered directly by the measles virus itself or by secondary bacterial infection. Inflammatory processes affect various systems:

In severely debilitated children, a life-threatening specific complication may develop — noma (progressive moist gangrene of the soft tissues of the maxillofacial region). With timely therapy, the prognosis is favorable, but emaciated patients retain a risk of mortality.

Pathologic Anatomy of Mumps

Mumps (epidemic parotitis) is caused by an RNA-containing paramyxovirus transmitted via droplets. The virus exhibits tropism for glandular tissues (parotid and pancreas glands, testes) and the nervous system. Primary replication occurs in the respiratory epithelium and lymph nodes.

Morphological picture:

  1. Parotid glands: the process is usually bilateral. The glands are sharply enlarged with a doughy consistency. Microscopically, marked edema and diffuse interstitial infiltration by plasma cells and lymphocytes are visible. The excretory ducts are compressed, accumulating cellular debris and neutrophils.
  2. Testes (orchitis): the tissue becomes edematous, infiltrated by mononuclear cells, with petechial hemorrhages. Due to severe swelling in a confined space, blood flow is compromised, leading to testicular infarctions. Outcome: sclerosis, atrophy, and male infertility.
  3. Pancreas: foci of necrosis surrounded by leukocyte clusters appear.
  4. Brain: viral encephalitis produces foci of demyelination and perivascular lymphoglial cuffs.

Infectious Mononucleosis and Poliomyelitis

Infectious mononucleosis is an anthroponotic disease caused by Epstein-Barr virus (EBV), predominantly affecting adolescents and young adults. The virus transmits via saliva, invades the oropharyngeal epithelium, and subsequently infects B lymphocytes, causing their polyclonal activation.

Pathomorphology of mononucleosis:

Poliomyelitis is an anthroponotic infection caused by an enterovirus (RNA-containing). It transmits via the fecal-oral route and specifically targets motor neurons of the central nervous system, leading to severe neurological deficits.

Mnemonic

To remember the pathognomonic sign of measles, use the association: "Measles involves UV rays" (Warthin-Finkeldey cells). For mononucleosis: "Mono means one, but lymph nodes, spleen, and liver are widely involved" (generalized lymphadenopathy, splenomegaly, hepatomegaly).

Frequently asked questions

What are the pathomorphological changes in the fauces and tonsils in scarlet fever?

Pathomorphological changes in the fauces and tonsils in scarlet fever present as a primary affect in the form of tonsillitis (angina), which sequentially passes through several stages.

  • Initial stage — catarrhal inflammation of the pharyngeal mucosa and tonsils with sharply demarcated hyperemia ("fiery throat") and palatal enanthema.
  • End of the first day — transition to catarrhal-purulent and purulent-necrotic inflammation (follicular, lacunar, or necrotic tonsillitis).
  • Outcome — sloughing of necrotic tissues forms an ulcerative-necrotic angina.
Which specific central nervous system structures are damaged in poliomyelitis?

Poliomyelitis specifically targets motor neurons (lower motor neurons) of the central nervous system.

  • Anterior horns of the spinal cord — selective, rapid, and irreversible cell death occurs.
  • Cervical and lumbar enlargements — the most frequent localization of motor neuron damage (predominantly in the lumbar region).

Destruction of these structures leads to flaccid paresis and paralysis with marked atrophy of the innervated muscles.

What is the nature and pathogenesis of the skin rash in scarlet fever?

The exanthem in scarlet fever is monomorphic, punctate, maculopapular, and set against a hyperemic background. The pathogenesis is driven by toxemia causing a generalized microvascular vasculitis.

  • Dermis — marked hyperemia, erythrocyte stasis, sludging, moderate perivascular edema, and lymphomacrophage infiltrates.
  • Epidermis — infiltrated by exudate; cells undergo keratinization and necrosis.

During resolution, desquamation occurs, presenting as large sheets on the palms and soles due to the thick epidermal layer.

What late infectious-allergic complications develop in the second to third week of scarlet fever?

During the second to third week of scarlet fever, sensitization and molecular mimicry lead to late allergic and autoimmune complications.

  • Acute glomerulonephritis — post-streptococcal renal injury with immune complex deposition on the glomerular basement membrane.
  • Myocarditis and/or endocarditis — rheumatic (allergic) heart involvement.
  • Arthritis (synovitis) — joint involvement mechanistically similar to rheumatic fever.
  • Rheumatic fever — a delayed consequence of streptococcal sensitization.

These complications are based on type IV hypersensitivity and cross-reactivity of antigens.

Which cells serve as the pathognomonic morphological sign of measles?

Warthin-Finkeldey multinucleated giant cells found within hyperplastic lymph node follicles.

What is the mechanism of infertility in mumps?

The virus causes pronounced edema and mononuclear infiltration of the testicular tissue. This leads to vascular compression, compromised blood supply, and parenchymal infarctions followed by sclerosis and atrophy.

What is noma and in which infection does it occur?

Noma is moist gangrene of the facial soft tissues, which can develop as a severe specific complication of measles in severely debilitated children.

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