In a patient over 50 years old with giant cell arteritis presenting with dyspnea, cough, and abnormal chest imaging, what pulmonary manifestations may occur and how should they be treated?

Pulmonary Manifestations of Giant Cell Arteritis

Respiratory involvement occurs in less than 10% of giant cell arteritis (GCA) cases, with chronic dry cough being the most frequent pulmonary symptom, and treatment with high-dose prednisone (40-60 mg daily) typically results in dramatic resolution of respiratory manifestations. 1, 2

Clinical Pulmonary Manifestations

Cough Characteristics

• Chronic dry cough is the predominant respiratory symptom, typically harsh and nonproductive, and may be the sole presenting feature of GCA in elderly patients. 1, 2
• Cough occurs in approximately 13.6% of GCA patients at initial presentation and may precede other classic manifestations of the disease. 3
• The cough is often associated with sore throat, hoarseness, and tenderness of cervical structures. 1
• In patients over 50 years with troublesome cough of "unknown etiology" and headaches, GCA should be strongly suspected. 1

Correlation with Disease Activity

• Dry cough correlates significantly with inflammatory markers: mean CRP is 153.8 mg/L in patients with cough versus 94 mg/L in those without (p = 0.0131). 3
• The presence of cough does not correlate with other clinical manifestations of GCA but is strongly associated with elevated inflammatory biomarkers. 3

Parenchymal and Vascular Lung Disease

• Interstitial lung disease (ILD) may occur, with the most common patterns being probable usual interstitial pneumonia (30%), indeterminate for usual interstitial pneumonia (22%), and combined pulmonary fibrosis and emphysema (13%). 4
• At ILD diagnosis, 52% of patients present with dyspnea, 26% with dry cough, and less commonly with wheezing or chest pain. 4
• Airway abnormalities are present in approximately 43% of GCA patients with respiratory involvement, including bronchial wall thickening (26%) and bronchiectasis (9%). 4
• Other documented pulmonary complications include isolated small airways disease, lung nodules, interstitial infiltrates, pulmonary artery vasculitis, and ill-defined granulomas within bronchial walls and alveolar interstitium. 1, 2
• Rare but serious manifestations include pulmonary artery obstruction due to direct vasculitic involvement. 5, 6

Pathophysiologic Mechanisms

• The mechanism of cough in GCA remains unknown, though it may result from ischemia caused by vasculitis affecting bronchial or pulmonary arteries. 1, 7
• The majority of GCA patients presenting with cough do not exhibit other pulmonary manifestations on imaging or pulmonary function testing. 1
• Respiratory symptoms may reflect lymphocytic airway inflammation or bronchoalveolar lymphocytosis as part of the systemic autoimmune process. 1

Diagnostic Approach in Patients with Respiratory Symptoms

Clinical Suspicion Triggers

• Any patient over 50 years with unexplained chronic dry cough and elevated inflammatory markers (ESR >40 mm/h or CRP ≥2.5 mg/dL) warrants evaluation for GCA. 1, 3
• Look specifically for concurrent headache, jaw claudication (LR+ 4.90), scalp tenderness (LR+ 3.14), temporal artery abnormalities (LR+ 4.70), or visual disturbances. 8

Laboratory Evaluation

• Measure ESR and CRP; ESR >100 mm/h has LR+ 3.11, while ESR <40 mm/h has LR- 0.18 (strongly excludes GCA). 8
• Check platelet count; values >400 × 10³/µL have LR+ 3.75. 8

Imaging Studies

• Obtain chest CT in patients with dyspnea or persistent cough to evaluate for ILD patterns, airway abnormalities, lung nodules, or interstitial infiltrates. 4
• Perform temporal artery ultrasound (sensitivity 88%, specificity 97% for "halo sign") or arrange temporal artery biopsy (≥1 cm specimen) within 2 weeks of starting treatment. 8
• Consider MR/CT angiography of neck, chest, abdomen, and pelvis to assess for large-vessel involvement and pulmonary artery vasculitis. 8

Treatment Algorithm

Immediate Management

1. Initiate high-dose oral prednisone 40-60 mg daily immediately upon clinical suspicion, without awaiting biopsy confirmation. 1, 8

• Do not delay treatment while arranging diagnostic studies; untreated GCA carries 14-50% risk of permanent vision loss. 8
• For patients with visual symptoms, administer IV methylprednisolone 500-1000 mg daily for 3 days before transitioning to oral therapy. 8

2. Add tocilizumab at diagnosis to reduce cumulative glucocorticoid exposure and prevent relapses. 8

• Use methotrexate as steroid-sparing alternative when tocilizumab is unavailable. 8

Response to Treatment

• Prednisone therapy dramatically resolves respiratory manifestations, including harsh cough, typically within days to weeks of initiation. 1
• Three of six patients with cough in one series improved after glucocorticoid initiation. 4
• Maintain initial high dose (40-60 mg daily) for one month, then taper to ≤5 mg/day by 12 months if disease controlled, guided by clinical symptoms and inflammatory markers. 8

Monitoring Respiratory Disease

• ILD may progress in some patients despite immunosuppressive therapy (35% showed progression on follow-up CT in one series). 4
• Repeat chest imaging if respiratory symptoms worsen or fail to improve with standard GCA treatment. 4
• Serial pulmonary function testing may be warranted in patients with documented ILD or airway disease. 4

Critical Pitfalls to Avoid

• Do not dismiss chronic dry cough in elderly patients as "bronchitis" or "post-viral" without checking inflammatory markers and considering GCA. 1, 3
• Do not attribute respiratory symptoms solely to heart failure or COPD in patients over 50 with elevated ESR/CRP; GCA can coexist or be the primary cause. 3
• Do not delay glucocorticoid therapy while pursuing extensive pulmonary workup if GCA is suspected; treatment can be initiated while diagnostic confirmation is pending. 8
• Do not assume absence of headache or visual symptoms excludes GCA; isolated respiratory manifestations can be the sole presenting feature. 3, 7
• Do not stop immunosuppression prematurely in patients with ILD, as some may require prolonged therapy beyond typical GCA treatment duration. 4

Prognosis of Pulmonary Involvement

• Cough typically resolves completely with appropriate glucocorticoid therapy when it is the primary respiratory manifestation. 1
• ILD associated with GCA has a more variable course, with some patients experiencing progression despite treatment. 4
• The duration of prednisone therapy depends on response of respiratory and other systemic symptoms, typically requiring 1-2 years of treatment. 1