Shwartzman phenomenon, also known as Shwartzman reaction, is a rare reaction of a body to particular types of toxins, called endotoxins, which cause thrombosis

Thrombosis

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

 in the affected tissue

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

. A clearing of the thrombosis results in a reticuloendothelial blockade, which prevents re-clearing of the thrombosis caused by a repeat introduction of the toxin. That will cause tissue necrosis

Necrosis

Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...

. Shwartzman phenomenon is usually observed during delivery or abortion, when foreign bodies are introduced into the tissues of the female reproductive system

Reproductive system

The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes...

.

The Shwartzman phenomenon is named for Gregory Shwartzman, the doctor at Mount Sinai Hospital

Mount Sinai Hospital, New York

Mount Sinai Hospital, founded in 1852, is one of the oldest and largest teaching hospitals in the United States. In 2011-2012, Mount Sinai Hospital was ranked as one of America's best hospitals by U.S...

 in New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 who was the first to develop the concept of immune system

Immune system

An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

hypersensitivity in the 1920s.
This reaction was experimented using Neisseria meningitidis endotoxin.