Drug-induced QT prolongation is often a result of treatment by antiarrhythmic drugs such as amiodarone and sotalol, antibiotics such as erythromycin, or antihistamines such as terfenadine. Other drugs which prolong the QT interval include some antipsychotics such as haloperidol and ziprasidone,  and the antidepressant citalopram. Lists of medications associated with prolongation of the QT interval such as the CredibleMeds database can be found online.Other causes of acquired LQTS include abnormally low levels of potassium (hypokalaemia) or magnesium (hypomagnesaemia) within the blood. This can be exacerbated following a sudden reduction in the blood supply to the heart (myocardial infarction), low levels of thyroid hormone (hypothyroidism), and a slow heart rate (bradycardia).Anorexia nervosa has been associated with sudden death, possibly due to QT prolongation. The malnutrition seen in this condition can sometimes affect the blood concentration of salts such as potassium, potentially leading to acquired long QT syndrome, in turn causing sudden cardiac death. The malnutrition and associated changes in salt balance develop over a prolonged period of time, and rapid refeeding may further disturb the salt imbalances, increasing the risk of arrhythmias. Care must therefore be taken to monitor electrolyte levels to avoid the complications of refeeding syndrome.Factors which prolong the QT interval are additive, meaning that a combination of factors (such as taking a QT-prolonging drug and having low levels of potassium) can cause a greater degree of QT prolongation than each factor alone.
Bowel-associated dermatosis–arthritis syndrome (BADAS), is a complication of jejunoileal bypass surgery consisting of flu-like symptoms (fever, malaise), multiple painful joints (polyarthralgia), muscle aches (myalgia) and skin changes. It has been reported to occur in up to 20% of patients who had jejunoileal bypass surgery, a form of obesity surgery that is rarely performed today.An excessive immune response to gut bacteria is thought to cause BADAS. Antibiotics have been used successfully to treat the condition (including tetracyclines, macrolides, metronidazole and fluoroquinolones). Corticosteroids are an alternative. Surgical repair of the normal bowel transit, where possible, can be effective. BADAS has later been reported in patients with inflammatory bowel disease, diverticulitis and following resection of the stomach (gastrectomy). BADAS has also been reported following biliopancreatic diversion (a form of bariatric surgery, also known as Scopinaro procedure), and in one case, BADAS occurred in a patient with acute appendicitis. Since "bowel bypass syndrome" is not applicable to these cases, the term BADAS was coined by Jorizzo and co-authors in 1984. Symptoms and signs
The most typical skin changes are a red patch (erythematous macula) with a central vesicle or pustule that heals without scarring. This maculopapular rash can recur every 4–6 weeks and predominantly affect the upper chest and arms. Erythema nodosum-like skin lesions can affect the legs. When a skin biopsy is examined under the microscope, there can be signs of a neutrophilic dermatosis. The joint pains in BADAS are typically episodic, migratory and affecting multiple joints. They can affect the small joints (e.g.