36 砷具有化學致癌性，其在皮膚的表現，下列敘述何者錯誤？

皮膚色素不均，有色素沈著或脫失的斑

掌蹠有角化

多發性原位癌易發生於陽光暴露部位

基底細胞癌與鱗狀上皮細胞癌，可單發、多發或同時出現

answer C

arsenic poisoning!!!!!!

Trivalent inorganic arsenic inhibits pyruvate dehydrogenase by binding to the sulfhydryl groups of dihydrolipoamide. Consequently, conversion of pyruvate to acetyl coenzyme A (CoA) is decreased, citric acid cycle activity is decreased, and production of cellular ATP is decreased. Trivalent arsenic inhibits numerous other cellular enzymes through sulfhydryl group binding. Trivalent arsenic inhibits cellular glucose uptake, gluconeogenesis, fatty acid oxidation, and further production of acetyl CoA; it also blocks the production of glutathione, which prevents cellular oxidative damage.

Effects of pentavalent inorganic arsenic occur partially because of its transformation to trivalent arsenic; toxicity proceeds as outlined above. More importantly, pentavalent arsenic resembles inorganic phosphate and substitutes for phosphate in glycolytic and cellular respiration pathways. Consequently, high-energy phosphate bonds are not made, and uncoupling of oxidative phosphorylation occurs. For example, in the presence of pentavalent arsenic, adenosine diphosphate (ADP) forms ADP-arsenate instead of ATP; the high-energy phosphate bonds of ATP are lost.

Physical

• Acute severe arsenic poisoning
  • Vital signs - Tachycardia and hypotension, even shock
  • CNS - Altered mental status, delirium, coma, and seizures (acute encephalopathy)
• Frequently, patients exposed to arsenic have a garlic smell to their breath and tissue fluids.
• In trivalent arsenic poisoning, clinical effects depend on the chronicity of exposure.
  • Acute exposures generally manifest with the cholera-like gastrointestinal symptoms of vomiting (often times bloody) and severe diarrhea (which may be rice-watery in character and often bloody); these patients will experience acute distress, dehydration (often), and hypovolemic shock.
  • Chronic toxicity is more insidious and may manifest as a classical dermatitis (hyperkeratosis with a classical "dew drops on a dusty road" appearance) or peripheral neuropathy (usually a painful paresthesia that is symmetrical and stocking-glove in distribution).
  • Also, whitish lines (Mees lines) that look much like traumatic injuries are found on the fingernails.
  • Multiple reports of cardiac arrhythmias exist in the literature. Reports of prolongation of the QT and ventricular fibrillation after acute arsenic intoxication make careful attention to cardiac status imperative.
  • Chronic hepatic and renal damage is common with chronic exposure.
• Arsine gas exposure manifests with an acute hemolytic anemia and striking chills. Hemoglobinuria causes the urine to appear black (see the image below), and the patient becomes rapidly obtunded and shocky. Shaking chills are often described in these patients.