A crush injury is injury by an object that causes compression of the body. This form of injury is rare in normal civilian practice, but common following a natural disaster. Other causes include industrial accidents, road traffic collisions, building collapse, accidents involving heavy plant, disaster relief or terrorist incidents. Presentation
Complications
Hypovolaemic Shock. Loss of plasma volume across damaged cell membranes and capillary walls can lead directly to severe hypovolaemia. Furthermore, shock can develop from myocardial depression following release of intracellular electrolytes. In addition, as a result of the mechanism of injury, blood loss from pelvic or long bone fractures may also co-exist. Hyperkalaemia and electrolyte imbalance. Disruption of cell membranes can result in a significant release of potassium, which is a largely intracellular cation that can precipitate cardiac arrest. Sequestration of plasma calcium into injured tissue can lead to a relative hypocalcaemia, which may worsen disruption of clotting abilities and shock. Metabolic acidosis may result from reperfusion injury and hypoperfusion related to shock. Compartment syndrome. Compartment syndrome is a common complication of crush injury as a consequence of oedematous tissue injury, redistribution of fluid into the intracellular compartment and bleeding. Established compartment syndrome may result in worsened systemic crush syndrome and irreversible muscle cell death. Acute Kidney Injury. Release of myoglobin by injured muscle leads to rhabdomyolysis coupled with shock leads to a significant rate of acute kidney injury, estimated as up to 15%. Acute kidney injury leads to a significantly higher mortality.
Beckers nevus (also known as "Beckers melanosis", "Beckers pigmentary hamartoma", "nevoid melanosis", and "pigmented hairy epidermal nevus") is a benign skin disorder predominantly affecting males. : 687  The nevus can be present at birth, but more often shows up around puberty. It generally first appears as an irregular pigmentation (melanosis or hyperpigmentation) on the torso or upper arm (though other areas of the  body can be affected), and gradually enlarges irregularly, becoming thickened and often hairy (hypertrichosis). The nevus is due to an overgrowth of the epidermis, pigment cells (melanocytes), and hair follicles. This form of nevus was first documented in 1948 by American dermatologist Samuel William Becker (1894–1964). Clinical information
Medical knowledge and documentation of this disorder is poor, likely due to a combination of factors including recent discovery, low prevalence, and the more or less aesthetic nature of the effects of the skin disorder. Thus the pathophysiology of Beckers nevus remains unclear. While it is generally considered an acquired rather than congenital disorder, there exists at least one case report documenting what researchers claim is a congenital Beckers nevus with genetic association: a 16-month-old boy with a hyperpigmented lesion on his right shoulder whose father has a similar lesion on his right shoulder. Prevalence
The most extensive study to date, a 1981 survey of nearly 20,000 French males aged 17 to 26, served to disprove many commonly held beliefs about the disorder. In the French study, 100 subjects were found to have Beckers nevi, revealing a prevalence of 0.52%.