T78.02XA Anaphylactic reaction due to shellfish (crustaceans), initial encounter

Name of the Condition

• Anaphylactic reaction due to shellfish (crustaceans), initial encounter (ICD-10 Code: T78.02XA)

Summary

This code is used to document an anaphylactic reaction specifically triggered by crustaceans (e.g., shrimp, crab, lobster) during the initial encounter. Anaphylaxis is a severe, potentially life-threatening allergic reaction that requires immediate medical attention. The code applies when the reaction is directly linked to shellfish exposure and meets clinical criteria for anaphylaxis.

Causes

Anaphylactic reactions due to shellfish occur when the immune system overreacts to proteins in crustaceans. The reaction is mediated by immunoglobulin E (IgE) antibodies, which release histamine and other chemicals, leading to rapid onset of symptoms. Even trace amounts of shellfish can trigger a reaction in sensitive individuals.

Risk Factors

• Previous history of shellfish allergy or anaphylaxis
• Family history of allergic conditions
• Asthma or other atopic diseases
• Exposure to crustaceans or shellfish-containing products
• Delayed administration of epinephrine during prior reactions

Symptoms

• Rapid onset of hives, itching, or swelling (especially of the lips, tongue, or throat)
• Difficulty breathing, wheezing, or stridor
• Drop in blood pressure (hypotension) or dizziness
• Nausea, vomiting, or abdominal cramps
• Loss of consciousness or confusion

Diagnosis

Diagnosis is based on clinical presentation and patient history. Key criteria include acute onset of symptoms after shellfish exposure, involvement of the skin, respiratory, or cardiovascular systems, and exclusion of other causes. Specific IgE testing or skin prick tests may confirm the allergy, but clinical judgment is primary.

Treatment Options

• Immediate administration of epinephrine (first-line treatment)
• Antihistamines or corticosteroids to manage symptoms
• Oxygen therapy or respiratory support if needed
• Intravenous fluids for hypotension
• Monitoring in a medical facility for recurrence

Prognosis and Follow-Up

With prompt treatment, most patients recover fully. Follow-up includes referral to an allergist for confirmation, education on avoidance, and prescription of an epinephrine auto-injector. Long-term prognosis depends on strict allergen avoidance and preparedness.

Complications

• Respiratory failure or arrest
• Cardiovascular collapse
• Asphyxiation from airway swelling
• Delayed biphasic reactions (recurrence of symptoms hours later)

Lifestyle & Prevention

• Avoid all crustacean-containing foods and cross-contamination risks
• Read food labels carefully for hidden shellfish ingredients
• Inform restaurants and food handlers of the allergy
• Carry an epinephrine auto-injector at all times
• Wear medical identification jewelry

When to Seek Professional Help

Seek emergency care immediately if symptoms of anaphylaxis occur, such as difficulty breathing, swelling, or dizziness. Do not wait for symptoms to worsen. Follow up with a healthcare provider to establish a management plan.

Tips for Medical Coders

Use T78.02XA for the initial encounter of an anaphylactic reaction due to crustaceans. Document the specific shellfish trigger, clinical manifestations, and treatment provided. Ensure the encounter is coded as "initial" (XA) if it is the first presentation of this reaction. Verify that the diagnosis meets anaphylaxis criteria to support code assignment.