WBR0067

Author	[[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Will Gibson and Yazan Daaboul)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biochemistry
Sub Category	SubCategory::General Principles
Prompt	[[Prompt::A 49-year-old male factory worker presents to the emergency department with complaints of weakness, abdominal cramps, vomiting and passage of loose "rice-water" stools. Physical examination reveals an abnormal cardiac rhythm, and peripheral motor and sensory neuropathy. Skin examination reveals hyperkeratosis of the palms and soles. The physician notes the patient's breath has a strong “garlic” odor. Which of the following is most likely responsible for this patient’s condition?]]
Answer A	AnswerA::Lead
Answer A Explanation	[[AnswerAExp::Lead poisoning usually occurs in children ingesting lead-based chipped paint from old houses. Clinical manifestations are cerebral edema, petechial hemorrhages, lead encephalopathy and peripheral neuropathy (such as wrist drop) with segmental demyelination and/or axonal degeneration. Lead lines are seen in bones on X-ray. In addition, anemia, and renal and GI symptoms could be manifested.]]
Answer B	AnswerB::Arsenic
Answer B Explanation	[[AnswerBExp::Arsenic poisoning usually occurs among factory workers who work with pesticides, wood preservatives, and ceramics. They become poisoned through either ingestion or inhalation. The typical symptoms are nausea and vomiting, abdominal pain, “rice water stools” and garlic breath.]]
Answer C	AnswerC::Mercury
Answer C Explanation	[[AnswerCExp::Sources of mercury include dental amalgam, batteries, wood preservatives and contaminated food. Mercury may be inhaled causing tremors, gingivitis, chest pain, pneumonitis, and confusion. Chronic exposure can lead to renal failure, acrodynia, and CNS manifestations.]]
Answer D	AnswerD::Cobalt
Answer D Explanation	[[AnswerDExp::Cobalt poisoning results from industrial use, medication, radioactive tracer, and cancer therapy. Toxicities include nausea, vomiting, paralysis, and hypotension.]]
Answer E	AnswerE::Organophosphate
Answer E Explanation	[[AnswerEExp::Organophosphate toxicity causes Diarrhea, Urination, Miosis, Bradycardia, Bronchoconstriction, CNS and muscle Excitation and Lacrimation, Salivation and Sweating (commonly used mnemonic: DUMBBBELSS).]]
Right Answer	RightAnswer::B
Explanation	[[Explanation::The patient most likely has arsenic poisoning, which is common among factory workers who work with pesticides, wood preservatives, and ceramics. Poisoning occurs either through ingestion or inhalation. Typical symptoms include gastrointestinal disturbances (nausea and vomiting, abdominal pain, and “rice water stools”), and sensory neuropathy/weakness. Because arsenic is a metabolic poison, highly metabolic tissues, such as the CNS, are typically impacted. In particular, patients may manifest signs suggestive of peripheral neuropathy. This neural pathology is thought to arise from segmental demyelination and axonal degeneration. One late complication of chronic arsenic exposure is angiosarcoma. Arsenic's toxic metabolite arsenite binds to the sulfhydryl (thiol) groups found in nearly all proteins with high affinity, thereby inhibiting their activity. While its mechanism of toxicity is highly pleiotropic, arsenic is considered a glycolytic poison that causes glycolysis to produce zero net ATP. Acute ingestion damages capillaries and small vessels, increasing permeability, and leading to hypoxia, transudation of fluid, inflammation, necrosis, and hypovolemia. Treatment should involve gastric lavage, IV hydration, and pharmacologic chelation with either dimercaprol or succimer. Penicillamine is no longer recommended for arsenic poisoning. Educational Objective: Arsenic is a potentially fatal metabolic poison that causes vomiting, rice-water stools, garlic breath, and hyperkeratosis of the palms and soles. References: Tournel G, Houssaye C, Humbert L, et al. Acute arsenic poisoning: Clinical, toxicological, histopathological, and forensic features. J Forensic Sci. 2011;56(s1):S275-9 First Aid 2014 page 101]]
Approved	Approved::Yes
Keyword	WBRKeyword::Poison, WBRKeyword::Arsenic poisoning, WBRKeyword::Toxin, WBRKeyword::Toxins, WBRKeyword::Arsenic, WBRKeyword::Biochemistry
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::