Differential Diagnosis

The patient's symptoms of progressive nausea, vomiting, diplopia, xerostomia, dysphagia, and diffuse weakness, along with the recent history of a salmon fishing trip in the Pacific Northwest, guide the differential diagnosis.

• Single Most Likely Diagnosis

  • Botulinum toxin: The patient's symptoms, such as diplopia (double vision), dysphagia (difficulty swallowing), xerostomia (dry mouth), and diffuse weakness, are classic for botulism. The recent salmon fishing trip is a significant clue, as improperly handled or preserved fish can be contaminated with Clostridium botulinum, the bacteria that produce botulinum toxin.

• Other Likely Diagnoses

  • Cholera toxin: While less likely given the symptom profile, cholera toxin from Vibrio cholerae could cause severe gastrointestinal symptoms. However, the primary symptom of cholera is profuse, watery diarrhea, which is not mentioned.
  • Staphylococcal enterotoxin: This toxin, produced by Staphylococcus aureus, can cause food poisoning with symptoms like vomiting and diarrhea. However, the neurological symptoms described are not typical for staphylococcal food poisoning.
  • Clostridium (Clostridioides) difficile toxin: C. difficile infection can cause severe diarrhea and abdominal symptoms, especially after antibiotic use, which is not mentioned in the patient's history. The neurological symptoms do not align well with C. difficile infection.

• Do Not Miss Diagnoses

  • Shiga toxin: Produced by certain strains of E. coli (e.g., E. coli O157:H7), Shiga toxin can cause severe foodborne illness, including hemolytic uremic syndrome (HUS), which is a medical emergency. Although the primary symptoms described do not perfectly align with those typically seen in Shiga toxin-producing E. coli infections (like severe diarrhea, potentially bloody), the potential severity of HUS makes it crucial not to miss.

• Rare Diagnoses

  • Other rare toxins or infectious agents could potentially cause similar symptom profiles, but given the information provided, they are less likely and would be considered only if more common causes are ruled out. Examples might include other bacterial or viral causes of foodborne illness with neurological manifestations.