Differential Diagnosis for Vomiting, Diarrhea, Blanching Rash, and Fever

Single Most Likely Diagnosis

• Viral Gastroenteritis: This is the most likely diagnosis due to the combination of vomiting, diarrhea, and fever, which are common symptoms of viral gastroenteritis. The blanching rash could be a non-specific symptom associated with the infection.

Other Likely Diagnoses

• Food Poisoning: Similar to viral gastroenteritis, food poisoning can cause vomiting, diarrhea, and fever. A blanching rash might occur in certain types of food poisoning, such as that caused by Staphylococcus aureus.
• Infectious Gastroenteritis (Bacterial): Bacterial infections like Salmonella or E. coli can lead to symptoms of gastroenteritis, including a rash in some cases.

Do Not Miss Diagnoses

• Meningococcal Septicemia: Although less common, this condition is life-threatening and can present with fever, rash (which can be blanching in early stages), and gastrointestinal symptoms like vomiting and diarrhea. Early recognition is crucial.
• Septic Shock: Any severe infection leading to septic shock could present with these symptoms, especially if there's an overwhelming bacterial infection. The rash might not always be the primary focus but could be part of a systemic response.

Rare Diagnoses

• Kawasaki Disease: This rare condition mainly affects children and can cause fever, rash, and gastrointestinal symptoms. It's essential to consider it in pediatric patients with these symptoms.
• Henoch-Schönlein Purpura (HSP): While HSP typically presents with a purpuric (non-blanching) rash, some cases might have an initial blanching phase. It's accompanied by abdominal pain, diarrhea, and sometimes vomiting, making it a rare but possible diagnosis.