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​Symptoms and Signs – Differential Diagnosis of Acute Watery and Bloody Diarrhea 
ACUTE WATERY DIARRHEA
• Gastrointestinal infections
• Protozoal (e.g., Giardia)
• Bacterial (e.g., enterotoxigenic Escherichia coli, cholera)
• Viral (e.g., rotavirus, Norwalk virus)
• Drugs
• Toxins
• Dietary constituents (e.g., lactose intolerance)
• Onset of chronic diarrheal illness
ACUTE BLOODY DIARRHEA
• Infectious colitis
• Confluent proctocolitis (e.g., Shigella, Campylobacter, Salmonella, Entamoeba histolytica)
• Segmental colitis (e.g., Campylobacter, Salmonella, enteroinvasive
E. coli, Aeromonas, E. histolytica)
• Drug-induced colitis (e.g., nonsteroidal anti-inflammatory drugs [NSAIDs])
• Inflammatory bowel disease
• Ischemic colitis (usually elderly patient with underlying heart disease or arrhythmias)
• Antibiotic-associated colitis
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​Symptoms and Signs – Differential Diagnosis of Diarrhea in  Tube-Fed Patient
(causal association with diarrhea not documented)
• Antibiotic-induced sterile gut
• Bacterial contamination of enteral products and delivery systems
• Elixir medications containing sorbitol
• Formula hyperosmolality (proven not to be the cause of diarrhea)
• High fat content of formula (in the presence of fat malabsorption syndrome)
• Inadequate fiber to form stool bulk
• Lactose (absent from nearly all enteral feeding formulas)
• Magnesium-containing antacids
• Pseudomembranous colitis
• Rapid advancement in rate (after the GI tract is unused for  prolonged periods) 
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​Symptoms and Signs – Differential Diagnosis of Depression
• Bipolar patients will frequently present with depression, but routine treatment with antidepressant medications may be detrimental in this group.
• Elderly patients: frequently coexists with dementia
• Hypothyroidism
• Major organ system disease (e.g., cardiovascular, liver, renal, neuronal diseases) with depressive symptoms
• Neurosyphilis
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Symptoms and Signs – Differential Diagnosis of de Quervain’s Tenosynovitis
• Carpal tunnel syndrome
• Compression neuropathy (e.g., superficial branch of the radial nerve “bracelet syndrome”)
• Gout
• Infection (e.g., TB, bacterial)
• Infiltrative tenosynovitis
• Ostearthritis

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​Symptoms and Signs – Differential Diagnosis of Atopic Dermatitis 
• Candidiasis
• Contact dermatitis
• Dermatitis herpetiformis
• Lichen simplex chronicus
• Other: Wiskott-Aldrich syndrome, phenylketonuria (PKU), mycosis fungoides, ichthyosis, HIV dermatitis, non-nummular eczema, histiocytosis X
• Photosensitivity
• Psoriasis
• Scabies
• Seborrheic dermatitis
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​Sympotms and Signs – Differential Diagnosis of Dermatographism
• Aquagenic urticaria
• Cholinergic urticaria
• Cold urticaria
• Exercise-induced urticaria
• Heat urticaria
• Lupus
• Polymorphous light eruption
• Solar urticaria
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