Loxoscelism Definition, Symptomns, Causes, Treatment

Loxoscelism is a condition that can be caused by a bite from a recluse spider. The skin surrounding the bite begins to deteriorate, and a shallow open sore develops (necrosis). It is the only form of necrotic arachnidism in humans that has been scientifically demonstrated. Research has been conducted on antibiotics, surgical intervention, hyperbaric oxygen, possible antivenoms, and vaccines; however, there is currently no recognized treatment that is successful for loxoscelism. Because there are so many diseases that can look like loxoscelism, doctors often make the wrong diagnosis.

The common term for spiders of the genus Loxosceles is "brown spiders." In medical science, the brown recluse spiders, also called Loxosceles reclusa, have become well-known. Their bites can result in clinical signs such as cutaneous necrosis and, on rare occasions, serious systemic manifestations like rhabdomyolysis, acute hemolytic anemia, and DIC. In endemic regions of the United States, such as some portions of the South, West, and Central Midwestern states, the brown recluse spider can frequently be found in dwellings. They love quiet places like basements, attics, or closets. In most cases, a recluse will only bite if they are being disturbed or threatened.

There are number of enzymes present in the venom of recluse spiders. However, Phospholipase D is one of these that is specific to Loxosceles and has pharmacological implications. 

Definition

A painful condition caused by the bite of a spider of the genus Loxosceles, particularly the brown recluse spider (L. reclusa), and characterized by localized necrosis of tissue and often systemic signs of poisoning.

Symptoms

Both local and generalized symptoms of loxoscelism can occur:

The reaction of loxoscelism that occurs only on the skin is referred to as necrotizing cutaneous loxoscelism. It is marked by a small, dead spot where the bite happened. The majority of people who are bitten by Loxosceles develop a mild skin irritation that clears up within seven days. Other wounds usually take 6 to 8 weeks to heal and can leave scars that last a long time.

The term "viscerocutaneous loxoscelism" describes a condition in which the skin and various organs are affected simultaneously. This happens rarely after being bitten by a Loxosceles. A lack of energy, along with nausea, vomiting, and a high temperature, are all symptoms. Hemolytic anemia, which results in blood cell destruction, can harm the kidney and necessitate transfusions. 

Children are the most likely to be affected by both the consumption of clotting factors (also known as disseminated intravascular coagulation, or "DIC") and the destruction of platelets (also known as thrombocytopenia). A DIC patient may experience a life-threatening hemorrhage. Rarely, myonecrosis and rhabdomyolysis may cause acute kidney failure, which might cause coma.

Causes

When a person is bitten by a Loxosceles spider, the bite can cause dermonecrosis or, rarely, a systemic condition that can be fatal. Venom activity is complex, and the process is yet not fully understood. The venom directly affects the cellular and basal membranes as well as the extracellular matrix, which causes the distinctive dermonecrotic lesion. 

The initial encounter between venom and tissues results in activation of the complement system, transition of polymorphic neutrophils, production of proteolytic enzymes, secretion of cytokines and chemokines, platelet aggregation, and abnormalities in blood flow that lead to edema, ischemia, and gangrene. There is currently no cure or treatment that is guaranteed to work for loxoscelism. Animal model studies demonstrate that even if specific antivenom is administered later, it may still be useful in reducing lesion size and preventing systemic disease.

Treatment

First aid should be used as the first step in treatment. Raise the limb so that it is above the level of the heart. Necrosis can be stopped by applying a cold compress to the area, as sphingomyelinase D activity is temperature-dependent.  Pain management can be accomplished with NSAIDs, but certain patients may require opioids instead. 

Antivenom, corticosteroids, and dapsone are the primary components of the therapy regimen for loxoscelism. The use of dapsone or antivenom, however, is not supported by any clinical trials, and there is very little research on the subject. Be aware that dapsone can have lethal hypersensitivity reactions and is dangerous to people who have G6PD deficiencies. There is evidence that corticosteroids are useful because of their ability to reduce hemolysis and aid in the prevention of renal failure.