Differential Diagnosis for a Child with Inadequate Weight Gain, Urticaria, and Biochemical Evidence of Egg Allergy

• Single most likely diagnosis:
  • Egg allergy with cross-reactivity or other food allergies: The child has biochemical evidence of an egg allergy, which could be causing the urticaria. The persistence of urticaria despite avoiding eggs might suggest cross-reactivity with other foods or the presence of another food allergy, contributing to inadequate weight gain due to malabsorption or increased metabolic demand from chronic inflammation.
• Other Likely diagnoses:
  • Atopic dermatitis with food allergy: Children with atopic dermatitis often have food allergies, including to eggs, which can cause skin symptoms like urticaria. The condition can lead to discomfort, affecting feeding and thus weight gain.
  • Gastroesophageal reflux disease (GERD): GERD can cause discomfort during feeding, leading to inadequate intake and weight gain issues. It might also trigger or worsen urticaria in susceptible individuals.
  • Food protein-induced enterocolitis syndrome (FPIES): This condition involves an immune reaction to food proteins, leading to gastrointestinal symptoms that could affect weight gain. While it typically presents with vomiting and diarrhea after ingestion of the culprit food, it could potentially cause urticaria in some cases.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Celiac disease: An autoimmune reaction to gluten can lead to malabsorption, causing inadequate weight gain. While it primarily causes gastrointestinal symptoms, some patients might present with skin manifestations like urticaria.
  • Hereditary angioedema: A genetic disorder that causes recurrent episodes of severe swelling, which could be mistaken for urticaria. It's crucial to differentiate this condition due to its potential for life-threatening airway obstruction.
  • Mastocytosis: A condition characterized by an accumulation of mast cells in one or more organs, which can cause a variety of symptoms including urticaria, gastrointestinal issues, and potentially failure to thrive.
• Rare diagnoses:
  • Eosinophilic gastrointestinal disorders (EGIDs): Conditions like eosinophilic esophagitis or gastroenteritis can cause feeding difficulties, failure to thrive, and might be associated with urticaria in some cases.
  • Autoimmune enteropathy: A rare condition characterized by autoimmune destruction of the intestinal lining, leading to malabsorption and potentially severe gastrointestinal and skin symptoms.