Presenting Complaints

The patient presents with a chief complaint of recurrent hives for the past 3 months.

History of Presenting Complaint

The patient, a 37-year-old female from New Zealand, reports developing red, itchy welts on her skin that come and go over the past 3 months. The hives typically appear on her trunk, arms, and legs, and can last anywhere from a few hours to a couple of days before resolving on their own. She notes that the hives seem to be worse in the evenings and sometimes after she eats certain foods, but she has not been able to identify any consistent triggers. The hives are accompanied by moderate itching, but she denies any swelling of the face, lips, or throat. She has tried over-the-counter antihistamines with partial relief of her symptoms.

Significant Positives & Negatives For Differentials

Chronic Urticaria

Positives:

• Recurrent, transient, pruritic hives lasting >6 weeks
• Lack of identifiable trigger
• No associated angioedema
• Partial response to antihistamines

Negatives:

• Sudden onset of hives
• Presence of angioedema
• Systemic symptoms (fever, joint pain, etc.)
• Poor response to antihistamines

Acute Urticaria

Positives:

• Sudden onset of hives
• Identifiable trigger (e.g., food, medication, infection)
• Rapid resolution of symptoms with antihistamine treatment

Negatives:

• Recurrent, persistent nature of symptoms
• Lack of clear precipitating factor
• Incomplete response to antihistamines

Angioedema

Positives:

• Presence of swelling of the face, lips, tongue, or throat
• Rapid onset and resolution of symptoms
• Family history of angioedema

Negatives:

• Isolated hives without associated swelling
• Lack of airway involvement
• No family history of angioedema

Mastocytosis

Positives:

• Recurrent hives and flushing
• Presence of extracutaneous symptoms (gastrointestinal, cardiovascular, neurological)
• Elevated serum tryptase levels

Negatives:

• Lack of systemic symptoms
• Normal tryptase levels
• No evidence of underlying mast cell disorder

Autoimmune Conditions (e.g., Thyroid Disease, Lupus)

Positives:

• Presence of other autoimmune or systemic symptoms
• Positive autoantibody tests
• Poor response to antihistamines alone

Negatives:

• Isolated hives without other autoimmune manifestations
• Normal autoantibody panel
• Adequate response to antihistamine therapy

Case Presentation

Based on the patient's history and the significant positives and negatives for the differential diagnoses, the most likely diagnosis is chronic urticaria. The recurrent, transient nature of the hives, lack of identifiable trigger, and partial response to antihistamines are all consistent with this diagnosis. Further workup, including laboratory tests and a detailed symptom diary, would be helpful to confirm the diagnosis and rule out other potential causes.