Type III Hypersensitivity Reaction in Patient with Recurrent Respiratory Symptoms
The patient's presentation of cough, joint pain, and breathlessness that resolved and then recurred after 6 months is most consistent with a Type III hypersensitivity reaction (answer C). 1
Characteristics of Type III Hypersensitivity
Type III hypersensitivity reactions are characterized by:
- Formation of immune complexes between antigens and antibodies
- Deposition of these complexes in tissues
- Activation of the complement cascade
- Recruitment of inflammatory cells
- Tissue damage from inflammatory mediators 1
The temporal pattern of symptoms resolving and then recurring after 6 months suggests repeated exposure to an antigen with subsequent immune complex formation, which is characteristic of Type III hypersensitivity reactions 1.
Clinical Correlation
This presentation is consistent with hypersensitivity pneumonitis, a classic Type III reaction that can present with:
- Respiratory symptoms (cough and breathlessness)
- Systemic symptoms (joint pain)
- Pattern of resolution and recurrence with re-exposure to the triggering antigen 1, 2
A specific example from the literature is tropical pulmonary eosinophilia, which presents with fever, dry cough, wheeze and breathlessness. Patients are often initially misdiagnosed as having asthma. Notably, relapses occur in 20% of cases necessitating re-treatment 3.
Why Not Other Types of Hypersensitivity?
Type I (IgE-mediated): These reactions typically cause immediate symptoms (minutes to hours) like anaphylaxis or acute asthma attacks. They don't typically resolve and recur with the 6-month pattern described 1, 4
Type II (cytotoxic): These reactions usually cause conditions like hemolytic anemia or thrombocytopenia through antibodies targeting cell surface antigens. The combination of respiratory symptoms with joint pain is not typical 1, 4
Type IV (delayed-type): While these can affect the lungs, they typically take 48-72 hours to develop and are seen in conditions like contact dermatitis. The joint involvement and specific recurrence pattern after 6 months are more consistent with Type III 1, 4
Clinical Implications
The recognition of this as a Type III hypersensitivity reaction guides management:
- Identify and remove the triggering antigen (which could be environmental or occupational)
- Consider corticosteroids for acute symptom management
- Monitor for potential progression to pulmonary fibrosis in cases of hypersensitivity pneumonitis
- Evaluate for multi-system involvement 1, 2
The recurrence after 6 months strongly suggests re-exposure to an antigen that triggered the initial immune complex formation, which is the hallmark of Type III hypersensitivity reactions.