Case Presentation: The patient is a 20-year-old male without past medical history. He began to feel depressed about 3 weeks prior to admission, and his dietary intake decreased. Concomitantly, he experienced diarrhea once to twice per day. He noticed pain in both the thighs when waking up the day before the admission. The pain persisted and gradually spread throughout the lower limbs. Because of difficulty in standing up, he presented to our emergency department.On admission, he was alert and his vital signs were normal. Blood tests revealed a potassium level of 1.9 mEq/l. The results of venous blood gas analysis were as follows: pH, 7.314, HCO3, 15 mmol/l, pCO2, 30.2 mmHg, anion gap, 17 mmol/l, and corrected HCO3, 20 mmol/l. These data suggested both high anion gap metabolic acidosis and normal anion gap metabolic acidosis. The urine pH was 5.5. The patient was admitted to our department with a diagnosis of hypokalemia due to type 1 renal tubular acidosis. Because diarrhea was mild, it was not sufficient to cause normal anion gap metabolic acidosis. The urinary hippuric acid concentration measured after going out on the 4th day of hospitalization was as high as 1.53 g/l. He had admitted to inhaling paint thinner in the past, but denied recent use; nevertheless, we diagnosed him with toluene intoxication because of these findings. After hospitalization, serum potassium concentration rapidly increased with the administration of a potassium supplement, and his symptoms also improved. He was discharged home on Day 6 of hospitalization.
Discussion: Toluene is the most widely abused inhalation volatile drug; in Japan, the number of arrests has decreased dramatically; there were 385 arrests in 2009, decreasing to seven arrests in 2018. We rarely see patients with toluene intoxication. Furthermore, toluene intoxication may exhibit various nonspecific symptoms such as central nervous system symptoms, respiratory symptoms, digestive tract symptoms, and kidney damage including renal tubular acidosis. Accordingly, toluene intoxication is difficult to diagnose. In such situations, blood gas analysis and evaluation of urine anion gap are important for proper diagnosis. Toluene intoxication gives rise to type 1 renal tubular acidosis and this can be the key to diagnosis. Whereas the anion gap does not normally increase in type 1 renal tubular acidosis, it may increase in toluene intoxication because of hippuric acid accumulation, and the blood gas findings in this case were consistent with toluene intoxication. Benzoic acid is found in soft drinks as a preservative and causes high urinary hippuric acid levels. However, as in this situation, urinary hippuric acid levels disappear over several hours. In the present case, the patient did not drink soft drinks during hospitalization; therefore, we believed his high urinary hippuric acid levels were caused by toluene intoxication.
Conclusions: We present a rare case of toluene intoxication that was diagnosed based on blood gas analysis and urinary hippuric acid levels. When you see type 1 renal tubular acidosis, you should consider the possibility of toluene intoxication and check urinary hippuric acid levels.