Ergotism is a rare condition caused by ingestion of alkaloids produced by Claviceps purpurea fungi, most commonly through the use of drugs for migraine headaches (methylergometrine, ergotamine or ergotoxine) and concomitant administration of cytochrome P450 3A4 inhibitors, including antiretrovirals and macrolide antibiotics. Marked vasoconstriction and arterial insufficiency are the principal causes of symptoms.
Symptoms stem from profound vasoconstrictive effects through blockade of alpha-adrenergic receptors, smooth muscle stimulation, and central sympatholytic activity, causing arterial insufficiency and development of both vascular and central nervous system complaints  . Vasospasm can affect virtually any vessel in the body, but most commonly involves the femoral artery, which is why lower extremities are the principal site of symptom occurrence . Initial reports showed that manifestations of ergotism may be seen as early as one hour after introduction of the harmful substance into the body , while other studies show that several days usually pass before the onset of symptoms . Limb ischemia, burning pain, impaired sensation followed by numbness, appearance of cold and pale skin of the affected extremities, eventually leading to claudication and gangrene is the typical clinical course if the condition is not recognized on time, and loss of the affected extremity has been reported     . In addition, central nervous systems symptoms are encountered as well, having in mind the fact that ergot alkaloids are derivatives of lysergic acid (LSD), one of the most potent psychoactive substances . Headaches, vertigo, hallucinations, mania, psychosis, convulsions (ranging from simple seizures to painful muscular contractions and tetanus-like cramps) and coma are constitutive features of ergotism  . Gastrointestinal irritation can also occur. It presents as nausea, vomiting, diarrhea and cramping abdominal pain .
The diagnosis of ergotism may be difficult to make, as approximately 0.001-0.002% of patients receiving ergot derivatives actually develop ergotism . The workup, however, should be thorough and consist of several steps. Firstly, a thorough patient history to confirm the use of ergot-containing drugs and other agents that interfere with the cytochrome P450 3A4 system should be obtained, as ergot derivatives are metabolized through this cytochrome pathway in the liver . Antiretrovirals, antidepressants, macrolide antibiotics (erythromycin, azithromycin), azole antifungals, but also grapefruit juice use the same pathway for metabolic degradation and virtually all patients who suffer from ergotism used some of the above-mentioned drugs . Angiography is the cornerstone of evaluation of the vascular system in the setting of ergotism, and a generalized intense arterial spasm, the formation of collateral vessels (more commonly seen in prolonged toxicity) and thrombosis may be encountered . Isolated spasms, multifocal stenoses, often described as "threadlike narrowing" of the vessel, is mentioned in various reports  , and a combination of medication history, clinical findings and results from angiography should be sufficient to make the diagnosis.