Differentials
Other vesicant exposure
SIGNS / SYMPTOMS
Sulfur mustard or Lewisite exposure.
Similar clinical presentation to mycotoxin skin contact.
Blistering and pain may typically be delayed with mustard exposure, with intense itching and a brown-yellow pigmentation at the contact site.
INVESTIGATIONS
Skin and clothing for arsenic: positive in Lewisite exposure.
Urine or blood sample: positive for sulfur mustard metabolites.
Botulism
SIGNS / SYMPTOMS
Similar clinical presentation with gastrointestinal distress (nausea, vomiting, diarrhoea), progressive muscle weakness, and paralysis.
INVESTIGATIONS
Mouse bioassay of serum, gastric secretions, stool, or food samples: identifies toxin of Clostridium botulinum.
Culture of food samples, gastric aspirates, or faecal material: identifies toxin of C botulinum.
Food poisoning (other causes)
SIGNS / SYMPTOMS
Similar clinical presentation with gastrointestinal distress (nausea, vomiting, diarrhoea); absence of immunological or haematological signs and symptoms.
INVESTIGATIONS
Stool culture: isolation of specific pathogen.
Stool ova and parasite exam: isolation of specific ova and/or parasite.
Marine toxins
SIGNS / SYMPTOMS
Progressive muscle weakness and paralysis.
History suggestive of contact with marine toxins.
INVESTIGATIONS
Diagnosis should be made clinically as confirmatory tests take too long to be useful in initial management.
High-performance liquid chromatography in flesh of seafood: positive for marine toxin.
Serum/urine toxin analysis (emerging as a potential test for marine toxin exposure): positive for marine toxin.
Organophosphate poisoning
SIGNS / SYMPTOMS
Pinpoint pupils, excessive secretions, distinctive odour of solvent, and fasciculations.
INVESTIGATIONS
Atropine therapeutic trial: lack of anticholinergic effects.
Plasma cholinesterase: decreased cholinesterase activity.
Ricin poisoning
SIGNS / SYMPTOMS
Similar clinical presentation; absence of painful skin symptoms.
INVESTIGATIONS
Diagnosis should be made clinically as confirmatory tests take too long to be useful in initial management.
Testing for ricin in environmental samples will need to be carried out at a designated laboratory.[27]
Toxic shock syndrome
SIGNS / SYMPTOMS
Similar clinical presentation but with earlier onset of fever and hypotension.
INVESTIGATIONS
Microscopy and culture (blood, wound, fluid, tissue): positive for group A streptococcus or Staphylococcus aureus.
Viral gastroenteritis
SIGNS / SYMPTOMS
Similar clinical presentation with gastrointestinal distress (nausea, vomiting, diarrhoea); absence of immunological or haematological signs and symptoms.
INVESTIGATIONS
Viral stool culture: positive for causative organism.
Food allergy/intolerance
SIGNS / SYMPTOMS
History of exposure to certain foods known to cause intolerance or allergies (milk, lactose, gluten) and relapsing symptoms with challenge; angio-oedema of the face and pharynx, bronchospasm, urticaria.
INVESTIGATIONS
Coeliac markers: positive in most patients with gluten intolerance.
Hydrogen breath test: helps in diagnosing lactose intolerance.
Colonoscopy and biopsies: help in diagnosing milk allergies.
Cholera
SIGNS / SYMPTOMS
Watery diarrhoea from acute gastroenteritis may develop and is characterised as 'rice-water diarrhoea'.
INVESTIGATIONS
Stool cultures for Vibrio cholerae (curved gram-negative rods).
Heavy metal poisoning
SIGNS / SYMPTOMS
Gastroenteritis is common with arsenic and thallium; lead may cause cramping.
INVESTIGATIONS
If metal poisoning is suspected, urine arsenic or thallium can be measured.
Whole blood should be measured for lead.
Colchicine poisoning
SIGNS / SYMPTOMS
Colchicum autumnale plant (autumn crocus or meadow saffron) exposure.
Gastroenteritis is common in early colchicine poisoning.
Chemotherapy medications
SIGNS / SYMPTOMS
May produce gastroenteritis.
INVESTIGATIONS
Review the clinical history with the patient.
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