What is the best treatment approach for an elderly patient with Polymyalgia Rheumatica (PMR) and osteomyelitis who is not an ideal candidate for high-dose steroids due to potential underlying health conditions?

Treatment of PMR in a Patient with Osteomyelitis

Start with low-dose oral prednisone (12.5 mg/day) combined with early methotrexate (7.5-10 mg/week) to minimize steroid exposure while adequately treating the PMR, given the infection risk from osteomyelitis. 1

Rationale for Lower-End Steroid Dosing

The 2015 EULAR/ACR guidelines recommend an initial prednisone dose range of 12.5-25 mg/day, with the lower end specifically intended for patients with relevant comorbidities and risk factors for glucocorticoid-related side effects 1. In patients with active infection like osteomyelitis, you should use the minimum effective dose (12.5 mg/day) rather than higher doses within the recommended range 1. Doses >30 mg/day are strongly contraindicated due to incontrovertible evidence of harm without additional benefit 1.

Early Methotrexate as Steroid-Sparing Strategy

Add methotrexate 7.5-10 mg/week orally from the outset rather than waiting for treatment failure 1. The guidelines specifically recommend early introduction of methotrexate in patients with:

• Risk factors or comorbidities where glucocorticoid-related adverse events are more likely 1
• High risk for prolonged therapy 1

The evidence supporting this approach is robust:

• Methotrexate plus prednisone resulted in 28/32 patients (88%) successfully discontinuing prednisone by 76 weeks versus only 16/30 (53%) on prednisone alone (p=0.003) 2
• The median cumulative prednisone dose was significantly lower with methotrexate (2.1 g vs 2.97 g, p=0.03) 2
• Fewer flare-ups occurred in the methotrexate group (15/32 vs 22/30, p=0.04) 2
• An earlier study showed methotrexate allowed use of 1.84 g versus 3.2 g prednisone over one year (p<0.0001) 3

Alternative: Intramuscular Methylprednisolone

Consider intramuscular methylprednisolone 120 mg every 3 weeks as an alternative if oral steroids pose unacceptable infection risk 1. This regimen may provide lower cumulative glucocorticoid exposure, though the evidence is limited and comes from a single trial 1. The dosing schedule is:

• 120 mg IM every 3 weeks until week 9 1
• 100 mg at week 12 1
• Monthly injections thereafter, reducing by 20 mg every 12 weeks until week 48 1
• Then reduce by 20 mg every 16 weeks until discontinuation 1

However, this approach failed to demonstrate significantly fewer side effects except for weight gain, and long-term benefits remain unknown 1.

Critical Monitoring and Tapering

Assess clinical response at 2-4 weeks; if inadequate improvement occurs, the PMR diagnosis should be questioned rather than escalating to high-dose steroids 1. For patients responding appropriately:

• Taper to 10 mg/day within 4-8 weeks 1
• Once remission is achieved, reduce by 1 mg every 4 weeks 1, 4
• Continue methotrexate throughout the taper to prevent relapse 1

Management of the Osteomyelitis Concurrently

While treating PMR, ensure the osteomyelitis receives appropriate antimicrobial therapy. The modest immunosuppression from low-dose prednisone (12.5 mg/day) plus methotrexate is generally manageable with adequate antibiotic coverage, but close monitoring for infection progression is essential. Doses >15 mg/day significantly increase infection risk and should be avoided 5.

Common Pitfalls to Avoid

• Do not use initial doses ≤7.5 mg/day as they are discouraged due to insufficient anti-inflammatory effect 1
• Never use doses >30 mg/day due to clear evidence of harm without benefit 1, 5
• Do not delay methotrexate initiation waiting for steroid failure—early introduction is key for steroid sparing in high-risk patients 1
• Do not rely on NSAIDs as primary therapy; a small case series suggesting ibuprofen efficacy 6 contradicts established guidelines and should not guide practice in this clinical scenario
• Ensure bone protection with calcium 800-1000 mg daily and vitamin D 400-800 units daily for all patients on chronic glucocorticoids 5