How are polymyalgia rheumatica (PMR) and interstitial lung disease (ILD) managed in patients with both conditions?

Management of Polymyalgia Rheumatica with Interstitial Lung Disease

Patients with both polymyalgia rheumatica (PMR) and interstitial lung disease (ILD) should be treated with glucocorticoids as first-line therapy, with consideration for steroid-sparing agents such as methotrexate for PMR and rituximab, mycophenolate, or cyclophosphamide for ILD management.

Relationship Between PMR and ILD

The association between PMR and ILD is not extensively documented in clinical guidelines, but several important connections exist:

• ILD can occur concurrently with PMR, though it is less common than in other systemic autoimmune rheumatic diseases (SARDs) 1
• In some cases, PMR may precede the development of ILD 2, 3
• When PMR and ILD co-exist, it's crucial to re-evaluate the diagnosis thoroughly to rule out other conditions such as seronegative rheumatoid arthritis or clinically amyopathic myositis 1

Assessment and Diagnosis

Initial Evaluation

• Pulmonary function tests (PFTs) at baseline for all PMR patients
• High-resolution CT (HRCT) scan for:
  • Patients with respiratory symptoms
  • High-risk patients
  • Those with abnormal PFTs 4

Risk Factors for ILD Development

• Male sex
• Older age at disease onset
• Longer disease duration
• Higher disease activity 4

Treatment Approach

First-Line Therapy for PMR-ILD

1. Glucocorticoids:
   • Initial dose: 10-20 mg/day prednisone for PMR component 4
   • For ILD component: 1 mg/kg/day prednisolone (or equivalent) for grade 2 ILD
   • For grade 3 ILD: 1-2 mg/kg/day methylprednisolone IV 4
   • Taper schedule:
     • Grade 2 ILD: Over 4-6 weeks after improvement to grade <1
     • Grade 3 ILD: Over 6-8 weeks after improvement to grade <1 4

Second-Line/Steroid-Sparing Therapy

For patients with inadequate response to glucocorticoids within 72 hours, consider:

1. Rituximab:

   • Preferred for ILD component, especially in progressive cases 4
   • 8 mg/kg, one dose and every 2 weeks if needed

2. Mycophenolate mofetil:

   • 1 g twice daily 4
   • Effective for ILD stabilization

3. Cyclophosphamide:

   • For severe or rapidly progressive ILD
   • IV administration preferred over oral 4

4. Tocilizumab:

   • 8 mg/kg, one dose and every 2 weeks if needed 4

5. IVIG:

   • 2 g/kg over 2-5 days
   • Particularly useful when rapid onset of action is desired 4

Management of Rapidly Progressive ILD

For rapidly progressive ILD in PMR patients:

1. Pulse IV methylprednisolone:

   • 500-1000 mg IV daily for 3 days
   • Follow with high-dose oral prednisone 5, 4

2. Combination therapy:

   • Add rituximab, cyclophosphamide, or mycophenolate after stabilization 5

Monitoring and Follow-up

1. Regular PFTs:

   • Yearly for stable patients
   • Every 3-6 months for high-risk patients 4

2. HRCT:

   • Repeat based on clinical deterioration or PFT decline

3. Disease activity assessment:

   • Monitor both PMR symptoms and respiratory status

Special Considerations

1. Referral for transplantation:

   • Consider early referral for lung transplantation if ILD progresses despite treatment 4, 5

2. Differential diagnosis:

   • When PMR and ILD coexist, thoroughly evaluate for other autoimmune conditions, particularly if:
     • Asthenia is poorly responsive to low-dose steroids
     • Respiratory symptoms precede or coincide with muscular symptoms 1

Treatment Algorithm

1. Mild PMR with stable ILD:

   • Prednisone 10-20 mg/day with slow taper
   • Monitor PFTs yearly

2. PMR with progressive ILD:

   • Higher-dose glucocorticoids (1 mg/kg/day)
   • Consider early addition of steroid-sparing agents
   • More frequent monitoring (PFTs every 3-6 months)

3. PMR with rapidly progressive ILD:

   • Pulse IV methylprednisolone
   • Add rituximab, cyclophosphamide, or mycophenolate
   • Consider IVIG for rapid response
   • Early referral for lung transplantation evaluation

The management of PMR-ILD requires close collaboration between rheumatologists and pulmonologists, with treatment decisions guided by the severity of both conditions and the patient's overall clinical status 4.