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Most scorpion venoms contain little or no cytotoxic enzymes, so that a sting produces little local tissue damage. An exception to this is the cytotoxic venom of Hemiscorpius lepturus, a scorpion from Iran. There are four factors which play a role in defining eventual symptoms: the quantity of venom introduced and its toxicity as well as the size and medical condition of the victim. Many scorpions without medical interest have venom that can kill a mouse, but when introduced into human beings only produces symptoms analogous to those of a bee sting. If there is an allergy to this venom, however, anaphylaxis can follow and death can result from a sting of even a "harmless" scorpion.
Rapidly developing pain at the site of the sting is characteristic. Swelling and local redness are often limited but can be quite serious, primarily with Hadrurus hirsutus (southwest USA), Buthus occitanus (northern Africa) and Isometres maculatus (Australia). Local necrosis is exceptional. Local paraesthesias can occur. Several South African scorpions can squirt venom up to one metre away. If this comes into contact with the cornea, a chemical keratitis with burning pain develops.
These can either develop quickly, within ten minutes, or - more rarely - slowly, after only 24 hours. More and more, doctors use a clinical gradation:
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Evolution from degree 1 to degree 4 can occur very quickly (sometimes within a half hour). Generalised fatigue with muscle stiffness and weakness, anxiety and restlessness are frequent. The tendon reflexes are hyperactive. Sometimes fasciculations, tremors and/or clonus develop. Convulsions are not unusual after Leiurus, Androctonus and Mesobuthus stings. The relaxation phase of the Achilles tendon reflex can be slowed. If the patient is able to stand, his of her gait will often be atactic. Tityus serrulatus often causes muscle weakness which can persist for a very long time. Tachypnoea and dyspnoea can be followed by respiratory arrest. There is a high risk of this complication following Centruroides stings. Centruroides sculpturatus (southern USA) is predominantly neurotoxic, and cardiovascular complications are generally absent. The effects of the venom on the central nervous system have not been adequately described. More often than not, they are minimal. Symptoms of orthosympathetic and parasympathetic stimulation can develop with agitation, hypersalivation, sweating, hyperthermia, nausea, vomiting and diarrhoea, and sometimes priapism. Miosis, mydriasis and anisocoria can occur. Sometimes mydriasis and bradycardia or extreme tachycardia develop. The patient can experience hypertension, cardiac arrhythmia (with or without heart failure) and pulmonary oedema. These symptoms are the result of a massive release of endogenous catecholamines from the sympathetic nervous system and the adrenal glands. Cardiovascular toxicity is pronounced in Leiurus quinquestriatus and Buthotus tamulus stings. Acute oedematous and/or haemorrhagic pancreatitis, rhabdomyolysis and diffuse intravascular coagulation can occur. Children are generally very restless, with crying and shouting, agitation, shaking, twisting and swinging of their limbs. The child cannot still sit. Mortality depends largely on age. Children, the elderly and people with a serious pre-existing medical condition have a substantially higher risk of death than adults.
