In a 26-year-old woman with a history of intermittent asthma who works in a research laboratory with rats and has six months of worsening shortness of breath, nasal and conjunctival erythema, mild eosinophilia, expiratory wheezing, hyperinflated lungs on radiography, and airway wall thickening with regional air trapping on CT (computed tomography), what is the most likely diagnosis?

Work-Exacerbated Asthma

This patient has work-exacerbated (work-aggravated) asthma, characterized by worsening of her pre-existing asthma due to occupational exposure to laboratory rats.

Diagnostic Reasoning

The clinical presentation clearly fits the definition of work-aggravated asthma as outlined in the European Respiratory Society guidelines 1. Work-aggravated asthma is defined as worsening of pre-existing asthma due to causes and conditions attributable to a particular occupational environment 1. The key distinguishing feature is that the patient has a concurrent history of asthma that was not induced by workplace exposure 1.

Critical Clinical Features Supporting This Diagnosis:

• Pre-existing asthma history: She has documented asthma requiring albuterol prior to her current symptoms
• Clear temporal relationship: Symptoms worsen during weekdays at work and improve on weekends/holidays
• Occupational exposure: Laboratory rats are well-known sources of allergenic proteins that can aggravate asthma 1
• Allergic features: Conjunctival and nasal erythema with clear secretions suggest IgE-mediated allergic response
• Mild eosinophilia (7%): Consistent with allergic/type 2 inflammation 2, 3
• Reversible airway obstruction: Expiratory wheezing and air trapping on CT indicate ongoing bronchospasm

Why Not the Other Diagnoses?

Hypersensitivity pneumonitis would present with:

• Restrictive rather than obstructive pattern on pulmonary function
• Ground-glass opacities and nodular infiltrates on CT, not just airway wall thickening
• Systemic symptoms (fever, malaise)
• Predominantly lymphocytic rather than eosinophilic inflammation

Bronchiolitis obliterans would show:

• Progressive, irreversible airflow obstruction
• No improvement away from work once established
• Mosaic attenuation pattern on CT
• Typically follows high-level toxic exposure, not chronic low-level allergen exposure

Vocal cord dysfunction would demonstrate:

• Inspiratory stridor rather than expiratory wheezing
• Normal spirometry between episodes
• No eosinophilia or allergic features
• Flattening of inspiratory loop on flow-volume curves

Management Implications

According to ERS guidelines, removing exposure to the causative agent leads to the best health outcome 1. For this patient:

1. Immediate intervention: The patient should be removed from direct rat exposure or reassigned to duties without animal contact
2. If complete removal impossible: Exposure reduction is the second-best option, though respirators have limited value 1
3. Optimize asthma therapy: Her current as-needed albuterol is insufficient; she likely needs controller therapy given the persistent symptoms
4. Early recognition is critical: Delayed intervention can lead to progressive, irreversible airway changes 1

Common Pitfall to Avoid:

Do not dismiss this as simply "stress-related" asthma because of her upcoming work evaluation. The clear temporal pattern with weekends/holidays, combined with allergic features and known rat allergen exposure, points definitively to occupational aggravation 1.

The 6-month duration of symptoms indicates this is not a transient issue and requires definitive workplace intervention to prevent permanent airway remodeling and progression to more severe, irreversible disease 1.