Toluene poisoning principally occurs through inhalation, either by intentional abuse or accidentally in the industrial setting, given its widespread use in the synthesis of organic solvents. Symptoms arise due to severe hypokalemia and metabolic acidosis, most prominent being weakness and paralysis, as well as neurological deficits and gastrointestinal irritation. Confirming exposure to toluene during history taking is crucial to make the diagnosis.
Toluene is an aromatic hydrocarbon used in the production of industrial solvents that are present in paints and various chemical substances, including pharmaceutical and sanitation products  . Thus, many occupations carry an increased risk for accidental exposure to higher concentrations of this compound. Toluene poisoning, however, is much more commonly encountered in individuals who intentionally abuse toluene through "glue sniffing", described as the second most common type of teenage substance abuse   . As a result, adolescents are the main patient group . Signs and symptoms appear due to the extensive production of hydrogen ions during its metabolic degradation in the liver, leading to two major pathological mechanisms responsible for symptom appearance - severe metabolic acidosis and hypokalemia   . Furthermore, toluene can deposit in adipose tissues, implying that its metabolism requires a significant amount of time after being introduced into the human body . Consequently, both acute and chronic forms of poisoning might be recognized. In the acute setting, euphoria, disinhibition, and tinnitus are prominent features . Conversely, profound muscle weakness (or even paralysis) is the main symptom of chronic toluene poisoning, accompanied by gastrointestinal complaints (abdominal pain, nausea, vomiting and hematemesis) and central nervous system (CNS) abnormalities - altered mental status, confusion, hallucinations, euphoria, depression, ataxia and visual deficits  . Fatigue, but also cardiac arrhythmias are reported by certain authors  . In severe cases, renal failure (developing on the grounds of rhabdomyolysis and marked acidosis) and acute respiratory distress syndrome (ARDS) may occur .
The diagnosis of toluene poisoning rests on the ability of the physician to recognize signs and symptoms and confirm exposure to this aromatic hydrocarbon. For this reason, a properly obtained patient history (often requiring hetero-anamnestic data) and a detailed physical examination are perhaps essential steps during the diagnostic workup. In the presence of characteristic signs and symptoms, patients should be asked about their occupancy and whether exposure to toluene could have possibly occurred at the workplace, while intentional abuse must also be excluded. Laboratory studies, particularly the acid-base status and urinalysis, is the next step in solidifying clinical suspicion, showing hypokalemia, hypophosphatemia and a normal (or sometimes elevated) anion gap acidosis    . In addition, kidney function tests will reveal elevated creatine kinase (CK) levels in the presence of renal impairment, whereas severely acidic urine is also a common feature  . Some studies have confirmed that chronic toluene poisoning leads to marked structural changes and demyelination in the CNS, and typical findings on magnetic resonance imaging (MRI) include lesions of the white matter that transmit a hyperintense signal on T2-weighted studies and hypointensity of the thalamus . Thus, imaging studies may be beneficial in the presence of neurological deficits.