# Thallium Poisoning: Case Report and Scoping Review on Diagnostic Delay and Therapeutic Outcome
## 3 Detailed Case Description
The patient added that the partition valve was always operated by her husband and that he had been away on business for a week. She did not know how to position the valve correctly. The information gathered prompted the doctors to request a water analysis from the relevant Regional Agency (ARPA), which, due to the urgency of the case, provided the report within a few days. Toxicological analyses were carried out by the national reference laboratory, situated in another Region. Plasma and urinary samples for barium and thallium were obtained on the second day after admission, but the results naturally arrived a few days later when the patient had already been discharged. However, based on the patient's clinical history, the doctors decided to start treatment with Prussian Blue (Radiogardase, 3 g \(\times\) 3/die) before receiving the results of the tests. Prussian Blue can attach to other oral medications (specifically, it may prevent tetracycline absorption) and vital nutrients while being taken orally. The gastrointestinal tract's electrolytes, such as potassium, can be bound by Prussian Blue, lowering serum potassium levels and causing asymptomatic hypokalaemia. As a result, throughout treatment, the serum electrolyte levels should be frequently checked. Patients with pre-existing cardiac arrhythmias and electrolyte abnormalities should exercise extra caution. Prussian Blue consumption may result in constipation. Fiber-based laxatives or a high-fiber diet may be used to treat this. Since Prussian Blue is essentially not absorbed, does not cross the placental barrier, and does not enter breast milk, there are no issues with using it during pregnancy or lactation. There are currently no known consequences to one's capacity to operate machinery and drive. The low toxicity of Prussian Blue made the clinically guided \"ex juveniles\" treatment advisable. The Prussian Blue treatment, that was started on the first day of hospitalization, immediately resulted in pain relief and a general improvement in symptoms. Twelve hours after the start of Prussian Blue therapy, the pain was noticeably reduced. In the following days, there was a significant improvement in the patient's clinical conditions: paresthesia, myalgias, and joint pains disappeared, and tenderness in her knee joints diminished. Table 1 reports the results of toxicological analyses conducted on the patient during hospitalization and over a period of several months after discharge. On the fifth day, the patient was discharged with instructions to remain in telematic contact with the Poison Control Center of the Gemelli General Hospital and to repeat the urine and plasma tests on the dates indicated by the center. The water quality was analyzed using inductively coupled plasma mass spectrometry (ICP-MS), according to the ISO 7294-2:2023 method [39]. When the water analyses became available, they indicated evident thallium contamination in the well water, with values off the scale. The laboratory provided the highest measurable value, 150 \(\upmu\)g/L, which is 75 times higher than the maximum United States Environmental Protection Agency (US EPA) safety value of 2 \(\upmu\)g/L for drinkable water. The levels of other elements (barium, chromium, copper, vanadium, aluminum, cadmium, arsenic, lead, mercury, boron, nickel, selenium, manganese, and antimony) in the well water were within the safety levels. Blood and urine were analyzed by dynamic cell reaction inductively coupled plasma mass spectrometry (DRC-ICP-MS). Toxicology tests indicated elevated urinary thallium levels from the second day of hospitalization, with increased urinary excretion during therapy (between the tenth and thirtieth day) and a subsequent reduction, which, nevertheless, reached normality only after 120 days. The plasma thallium levels were very high on admission (267 times the upper reference limit) and showed a gradual reduction but failed to return to normal after 30 days of treatment.