A middle aged man presents with parasthesia of hands and feet. Examination reveals presence of 'Mees' lines in the nails and rain drop pigmentation in the hands. The most likely causative toxin for the above mentioned symptoms is -

Arsenic Mechanism of Action * Arsenic reversibly combines with sulphydrl enzymes. It blocks Krebs cycle and interrupts oxidative phosphorylation causing depletion of ATP and death of cell. * It also inhibits transformation of thiamine into acetyl CoA and Succinyl -CoA resulting in thiamine deficiency. * It replaces the phosphorus in the bones * Arsenic is incorporated into hair, nails and skin. * It causes increased permeability of small blood vessels with inflammation and necrosis of intestinal mucosa thus causing manifestation of hemorrhagic gastroenteritis. Clinical Features Acute poisoning A patient with acute arsenic consumption may present in 1. Fulminant type: collapse and circulatory failure 2. Gastroenteritis type-constriction of throat,difficulty in swallowing,rice water stools,hepatic fatty infiltration,headache,veigo,hypehermia 3. Narcotic form * Metallic taste * Garlicky odour * Nausea and vomiting * Colicky abdominal pain * Profuse diarrhea resembling rice water stool of cholera. * Circulatory failure * Intense thirst * Oliguria * Uremia * Ventricular tachycardia * Headache * Veigo * Tremors * Convulsions * Formication * Delirium * Tenderness in muscle * Paralysis * Hyperpyrexia * QT prolongation, tachyarrhythmia including torsades de pointes may develop within first 24 hours after ingestion. Chronic Arsenic Poisoning Skin - generalized or localized fine mottled pigmentation of skin (Rain drop pigmentation) Nails - become brittle and show Mees' line. Mees' line are white transverse lines over nails Hairs - dry and may fall off; patchy or diffuse alopecia Arsenic dust - flexor eczema, painless perforationof nasal septum. Liver enlarged (hepatomegaly) and cirrhotic Weakness of muscle and atrophy - extensor muscles more commonly affected resulting in wrist drop and foot drop CNS-polyneuritis,optic neuritis Eyes-congestion,watering of eyes,photophobia GIT-cirrhosis of liver,nausea,vomiting,abd cramp,diarrhoea,salivation CVS-cardiac failure,dependent edema Hematologic-* Leukopenia * Thrombocytopenia * Mild eosinophilia * Karyorrhexis - manifested by bizarre nuclear forms * Megaloblastic anemia * Basophilic stippling RS-cough,hemoptysis REF;THE SYNOPSIS OF FORENSIC MEDICINE:KS NARAYANA REDDY;28th EDITION;PAGE NO 305