Acute pancreatitis is an inflammation of the pancreas (and sometimes surrounding tissues) caused by the release of activated pancreatic enzymes. The main triggers of the disease are biliary tract diseases and chronic alcohol abuse.

Measles is an acute infectious disease of viral etiology, occurring with characteristic fever (38-39°C), catarrhal inflammation of the mucous membrane of the eyes, nasopharynx, pharynx and upper respiratory tract, specific rashes on the mucous membrane of the oral cavity, maculopapular rash on the skin.

Acute otitis media is an acute inflammatory disease characterized by the involvement of the mucous membrane of the middle ear (auditory tube, tympanic cavity, cave and air cells of the mastoid process) in the pathological process.

Acute obstructive bronchitis is acute bronchitis with bronchial obstruction syndrome. Acute obstructive bronchitis is characterized by wheezing. Acute bronchiolitis is a type of acute obstructive bronchitis with damage to small bronchi and bronchioles. Bronchiolitis is characterized by respiratory failure and an abundance of fine-bubble wheezing (children in the first two years of life are more often affected).

Acute myeloid leukemia accounts for one fifth of all acute leukemias in children. The prevalence of acute myeloid leukemia worldwide is approximately the same, at 5.6 cases per 1,000,000 children.

The causative agent of acute lymphocytic choriomeningitis is a filterable virus isolated by Armstrong and Lilly in 1934. The main reservoir of the virus is gray house mice, which excrete the pathogen with nasal mucus, urine and feces. Humans become infected by eating food products infected by mice, as well as by airborne droplets when inhaling dust. Acute lymphocytic choriomeningitis is often sporadic, but epidemic outbreaks are also possible.

Acute lymphoblastic leukemia is a group of clinically heterogeneous clonal malignancies of lymphocyte precursor cells that usually share distinct genetic and immunophenotypic characteristics. Secondary abnormalities in cellular differentiation and/or proliferation result in increased production and accumulation of lymphoblasts in the bone marrow and infiltration of lymph nodes and parenchymatous organs. Untreated acute lymphoblastic leukemia rapidly becomes fatal.

Acute liver failure (ALF) is a rapidly developing disorder of the synthetic function of the liver, characterized by severe coagulopathy and hepatic encephalopathy.

Acute leukemia occurs when a hematopoietic stem cell undergoes malignant transformation into a primitive, undifferentiated cell with an abnormal lifespan. Lymphoblasts (ALL) or myeloblasts (AML) exhibit abnormal proliferative capacity, displacing normal bone marrow and hematopoietic cells, inducing anemia, thrombocytopenia, and granulocytopenia.