Differential Diagnosis for Immediate Swollen Tender Bilateral Submandibular Lymph Nodes after Taking Lactase Supplements

• Single Most Likely Diagnosis
  • Allergic reaction to lactase supplements: This is the most likely diagnosis because the symptoms occurred immediately after taking the supplements, suggesting an immune-mediated response. Lactase is an enzyme derived from yeast or bacteria, and some individuals may be allergic to these sources.
• Other Likely Diagnoses
  • Infection (viral or bacterial): Although less likely given the temporal relationship with lactase supplement intake, infections can cause lymphadenopathy. However, the bilateral and immediate onset makes this less probable.
  • Angioedema: This condition can cause swelling but typically involves the face, lips, and tongue. However, it could be considered if the swelling is part of a more generalized reaction.
• Do Not Miss Diagnoses
  • Anaphylaxis: Although the symptoms described do not fully meet the criteria for anaphylaxis (which typically includes respiratory distress, cardiovascular instability, and/or gastrointestinal symptoms in addition to cutaneous or mucosal symptoms), any allergic reaction has the potential to progress to anaphylaxis, which is life-threatening and requires immediate intervention.
  • Serum sickness: This is a systemic immune complex-mediated hypersensitivity reaction that can occur after the administration of foreign proteins (including enzymes like lactase). It typically presents a week or more after exposure but can be considered in the differential for severe reactions.
• Rare Diagnoses
  • Sarcoidosis: This is a systemic granulomatous disease that can cause lymphadenopathy but is less likely given the acute onset and specific temporal relationship with lactase supplement intake.
  • Lymphoma: Although lymphoma can cause lymphadenopathy, it is rare and typically presents with more systemic symptoms and a slower progression.

Treatment

The treatment will depend on the underlying cause. For an allergic reaction, discontinuation of the lactase supplements and administration of antihistamines or corticosteroids may be necessary. In cases of anaphylaxis or serum sickness, immediate medical attention is required, with treatment including epinephrine, antihistamines, corticosteroids, and supportive care. For infections, appropriate antimicrobial therapy would be indicated. Rare diagnoses like sarcoidosis or lymphoma would require specific treatments tailored to the condition.