What macroscopic changes occur in regional lymph nodes during yersinial mesenteric lymphadenitis?

In yersinial mesenteric lymphadenitis, regional lymph nodes are infiltrated by leukocytes and matted together into conglomerate packs. Microabscesses may form.

What local intestinal complications can develop in severe yersiniosis?

The abdominal form of yersiniosis can lead to local intestinal complications: intestinal hemorrhage, ulceration, necrosis and perforation of the small and large intestines, peritonitis, diverticulitis, toxic megacolon, and ileocecal intussusception. Dysbiosis and intestinal wall perforation are also noted.

What extraintestinal immunopathological complications are characteristic of yersiniosis?

Extraintestinal non-suppurative complications and secondary-focal clinical variants are described for yersiniosis. These include Reiter syndrome, erythema nodosum, arthritis, arthralgia, exanthem, and post-infectious fatigue syndrome. In the scarlet fever-like variant, cases of acute interstitial nephritis and hemolytic-uremic syndrome have been reported.

What morphological changes develop in the liver in the generalized form of yersiniosis?

In the generalized form of yersiniosis, inflammatory and purulent-destructive processes develop in the liver. Macroscopically, hepatomegaly (enlargement of the liver) is observed. Abscesses form within the organ parenchyma. Yersinial hepatitis also develops, typically presenting in an anicteric form. A more detailed description of microscopic morphological liver changes is absent in the sources.

Which microorganisms cause yersiniosis?

The causative agents are Yersinia enterocolitica and Yersinia pseudotuberculosis, which are intracellular parasites related to the plague bacterium.

What are the primary target organs in yersiniosis?

The main target organs are the terminal ileum, the cecum, and regional lymph nodes.

How do yersinial granulomas differ from tuberculous granulomas?

Unlike tuberculous granulomas, yersinial granulomas invariably undergo suppuration with the formation of abscesses.

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Yersiniosis

For medical students2 min readUpdated 2026-10-10

Yersiniosis is an infectious disease caused by intracellular parasites of the genus Yersinia, transmitted via the fecal-oral route. The disease primarily affects the digestive tract, predominantly the terminal ileum and cecum, involving the lymphatic system.

Causative agentsYersinia enterocolitica and Yersinia pseudotuberculosis

Target organsTerminal ileum, cecum

Clinical formsAbdominal, appendicular, and generalized

Generalized mortalityUp to 50% in the generalized form

Etiology and Pathogenesis

The causative agents of yersiniosis are the bacteria Yersinia enterocolitica and Yersinia pseudotuberculosis, which are genetically related to the plague pathogen and act as intracellular parasites that destroy cells using specific enzymes. The primary natural reservoirs and sources of infection are rodents and cats, with transmission occurring via the fecal-oral route; children are affected most frequently. While certain endemic regions exist, sporadic cases are reported worldwide.

The portal of entry and primary site of infection are frequently the tonsils, which can initially manifest clinically as tonsillitis or pharyngitis. Subsequently, the pathogen spreads through the digestive tract, targeting the terminal ileum and cecum as the primary organs.

Clinical and Morphological Forms

In the pathologic anatomy of yersiniosis, three main clinical and morphological forms are distinguished:

Abdominal form — characterized by catarrhal or catarrhal-ulcerative gastroenteritis, gastroenterocolitis, and terminal ileitis. The intestinal wall is infiltrated by neutrophils, lymphocytes, plasma cells, and a small number of eosinophils. Hyperplasia and ulceration of Peyer's patches are observed in the lymphoid tissue.
Appendicular form — presents as a combination of acute appendicitis, terminal ileitis, and mesenteric lymphadenitis.
Generalized form — develops against the background of immunodeficiencies, anemias (especially iron deficiency anemia), and renal pathology. It is characterized by vasculitis, thrombovasculitis, and rash, with a mortality rate reaching 50%.

Morphology of Lymph Nodes and Granulomas

Regional lymph nodes are involved in the inflammatory process during yersiniosis (mesenteric lymphadenitis): they become infiltrated by leukocytes, matted together into conglomerate packs, and may develop microabscesses, while the spleen undergoes hyperplasia.

Occasionally, specific yersinial granulomas (pseudotuberculosis) form within the intestinal mucosa against a background of catarrhal or catarrhal-erosive inflammation with diffuse eosinophilic infiltration. Structurally, they resemble tuberculous granulomas—containing epithelioid cells, macrophages, and sometimes Langhans giant cells, with a necrotic center exhibiting karyorrhexis. The main difference from tuberculosis is that yersinial granulomas undergo suppuration with abscess formation, resolving via scar formation.

Complications and Prognosis

The pathologic process may be accompanied by various complications, among which are:

Intestinal hemorrhage and bowel wall perforation;
Bacterial infections of the respiratory tract and middle ear;
Dysbiosis.

In most cases, the prognosis for yersiniosis is favorable, ending in recovery, although relapses and progression to a chronic course are possible. The generalized form of the infection carries an unfavorable prognosis.

Mnemonic

Yersiniosis targets the Ileum (terminal ileitis) and Lymph nodes (mesenteric lymphadenitis with matted node packs), and its granulomas are easily distinguished from tuberculosis by their tendency to suppurate.

Frequently asked questions

What macroscopic changes occur in regional lymph nodes during yersinial mesenteric lymphadenitis?: In yersinial mesenteric lymphadenitis, regional lymph nodes are infiltrated by leukocytes and matted together into conglomerate packs. Microabscesses may form.
What local intestinal complications can develop in severe yersiniosis?: The abdominal form of yersiniosis can lead to local intestinal complications: intestinal hemorrhage, ulceration, necrosis and perforation of the small and large intestines, peritonitis, diverticulitis, toxic megacolon, and ileocecal intussusception. Dysbiosis and intestinal wall perforation are also noted.
What extraintestinal immunopathological complications are characteristic of yersiniosis?: Extraintestinal non-suppurative complications and secondary-focal clinical variants are described for yersiniosis. These include Reiter syndrome, erythema nodosum, arthritis, arthralgia, exanthem, and post-infectious fatigue syndrome. In the scarlet fever-like variant, cases of acute interstitial nephritis and hemolytic-uremic syndrome have been reported.
What morphological changes develop in the liver in the generalized form of yersiniosis?: In the generalized form of yersiniosis, inflammatory and purulent-destructive processes develop in the liver. Macroscopically, hepatomegaly (enlargement of the liver) is observed. Abscesses form within the organ parenchyma. Yersinial hepatitis also develops, typically presenting in an anicteric form. A more detailed description of microscopic morphological liver changes is absent in the sources.
Which microorganisms cause yersiniosis?: The causative agents are Yersinia enterocolitica and Yersinia pseudotuberculosis, which are intracellular parasites related to the plague bacterium.
What are the primary target organs in yersiniosis?: The main target organs are the terminal ileum, the cecum, and regional lymph nodes.
How do yersinial granulomas differ from tuberculous granulomas?: Unlike tuberculous granulomas, yersinial granulomas invariably undergo suppuration with the formation of abscesses.

Go deeper

Epidemiology and sources of infection
Features of abdominal ileitis
Morphological picture of mesenteric lymphadenitis
Differences between pseudotuberculous granulomas and tuberculosis
Pathogenesis and causes of the generalized form