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Tuesday, January 06, 2009

A middle aged man from West Bengal presents with paraesthesia of hands and feet, hyperkeratosis, lines in the nails and rain drop pigmentation in the hands.

Question 72
59. A middle aged man from West Bengal presents with paraesthesia of hands and feet, hyperkeratosis, lines in the nails and rain drop pigmentation in the hands. The most likely causative toxin for the above mentioned symptoms is:
1. Lead.
2. Arsenic
3. Thallium.
4. Mercury.
Answer
2. Arsenic
Reference
The Essentials of Forensic Medicine and Toxicology 21st Edition : K.S.Narayana Reddy Page 462
P.C.Dikshit 1st Edition Page 477
Quality
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QTDF
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Discussion
Ä     Arsenic is termed a metalloid as it has properties of both metals and non-metals.
Ä     Forms
o       Trivalent (e.g. arsenic trioxide, arsenious acid, and arsenites) and
o       Pentavalent (e.g. arsenic pentoxide, arsenic acid, and arsenates) derivatives.
o       Inorganic arsenical compounds may generate arsine gas when in contact with acids and reducing metals (e.g. iron and zinc) or with sodium hydroxide and aluminium.
Ä     Use
o       Electronics industry,
o       Production of special types of crystal and optical glass,
o       Hardening lead and copper alloys,
o       Manufacture of fireworks,
o       Wood preservative and
o       Pesticide. It is a byproduct of copper smelting.
Ä     In exposed individuals high concentrations of arsenic are present in
o       Bone,
o       Hair, and
o       Nails. The half-life is in the range of 1 to 3 days.
Ä     Excretion is predominantly in the
o       urine as mono- and dimethyl-derivatives.
CLINICAL FEATURES
Ä     Acute poisoning
o       This can follow accidental, suicidal, or deliberate ingestion,
o       Toxicity being largely dependent on the water solubility of the ingested compound.
§        Within 2 h of substantial ingestion of a soluble arsenical compound, severe haemorrhagic gastritis or gastroenteritis may ensue with collapse and death usually within 4 days.
§        A metallic taste, salivation, muscular cramps, facial oedema, difficulty in swallowing, hepatorenal dysfunction, convulsions, and encephalopthy are reported.
§        A peripheral neuropathy (predominantly sensory), striate leukonychia (Mees' lines) and hyperkeratotic, hyperpigmentated skin lesions are common in those surviving a near fatal ingestion.
§        In moderate or severe arsenic poisoning investigations may show anaemia, leucopenia, thrombocytopenia, and disseminated intravascular coagulation. ECG abnormalities have been reported and include QT prolongation and ventricular arrhythmias.
o       Exposure to arsenic trioxide and trichloride dust causes irritation of the eyes, nose, throat, and lower respiratory tract. Corrosive skin damage may follow skin contact with arsenical compounds such as arsenious acid and arsenic trichloride.
Ä     Chronic poisoning
o       Source
§        Contaminated drinking water or
§        “Tonics” containing inorganic trivalent arsenical compounds
o       Features
§        Progressive weakness,
§        Anorexia, Nausea, Vomiting, Stomatitis, Colitis,
§        Increased salivation, Epistaxis, Bleeding gums, Conjunctivitis,
§        Weight loss, and Low grade fever.
§        Hyperkeratosis (palms and soles of the feet)
§        “Raindrop” (skin),
§        “Mees” (nails).
§        Skin cancer (usually squamous cell epithelioma)
§        A symmetrical peripheral neuropathy is typical.
§        Sensory symptoms predominate but motor involvement is also
§        Central nervous system effects
·        hearing loss,
·        psychological impairment and
·        EEG changes.
§        disturbances of liver function
§        Ulceration and perforation of the nasal septum.
Ä     Chronic exposure to trivalent and pentavalent forms of arsenic has been linked to excess lung cancer and lung cancer occurring in lead, tin, and copper smelter workers has been attributed to arsenic.
Explanation
1. Lead poisoning presents with a whole lot of features like Aneamia, Colic, Neuropathy, facial pallor, lead line or Burtonian line, lead encephalopathy , optic atrophy etc.
2. Acute Arsenic Resembles Diarrhoea where as Chronic Arsenic resembles “fading Measles
3. Thallium poisoning resembles Guillain Barre Syndrome.
4. Minamita disease, hatter’s shakes and mercurial erethesm are a few of the prominent features of Mercury Poisoning.
Comments
TREATMENT :
Ä     Dimercaprol (British Anti-Lewisite, BAL) given by deep intramuscular injection (2.5-5 mg/kg four hourly for 2 days followed by 2.5 mg/kg intramuscularly twice daily for 1 to 2 weeks).
Ä     DMSA (succimer) and DMPS (unithiol) are more effective in reducing the arsenic content of tissues and, unlike dimercaprol they do not cause accumulation of arsenic in the brain DMSA and DMPS may be given orally (in a dose of 30 mg/kg body weight daily).
Tips
The fact that Arsenic is tasteless and odorless was known even eras ago. It is alleged that the governor of St.Helena “slow poisoned” the “petit corporal” while he was in the jail as a prisoner of Britain. But they didn’t perhaps know that Arsenic is a BAD homicidal poison as it can be detected even centuries after in Bone and Hair (as was detected from Napolean’s mortal remains).

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