PMR/Statin induced myopathy

Question 1

A 63 year old woman complains of aching shoulders and hips for the past month. She has not noticed any weakness but the pain is affecting her activities. Apart from the pain she feels tired but her appetite is good and her weight is stable. Her past health is unremarkable except for hypercholesterolemia which was diagnosed three months ago and is being treated with simvastatin. How would you assess and manage her?

Imp/DDx/Goals

Answer 1

Impression
Given presentation and medications history, provisionally suspect a statin-induced myopathy which affects 10% of statin users (simvastatin carries greatest risk for myopathy).

DDx:
Aching shoulder and hip girdle is classically a presentation of polymyalgia rheumatica (PMR). Would want to consider other systemic rheumatological conditions including polymyositis, dermatomyositis, and inflammatory arthropathy. Rule out rhabdomyolysis.
Also consider osteoarthritis as a potential differential (if more joint-pain).

Goals:

• identify underlying cause of myopathy with comprehensive assessment
• initiate appropriate management

Question 2

Statin induced myopathy - History

Answer 2

History:

• sx: pain, nature, time-course, characterise whether muscle or joint pain/tenderness, weakness, morning stiffness? (PMR). Ask about any GCA symptoms, what muscles are affected
• RED flags: muscle pain, weakness, dark urine (rhabdo triad)
• Statin: when started, temporal relationship?
• PMHx: autoimmune disease, previous episodes. medical conditions which increase risk of statin myopathy (CKD, hypothyroidism, Vit D deficiency)
• Assess degree of function that is impaired (ADLs)
• Medications: statins and other, temporality to muscle sx
• SNAP

Question 3

Statin induced myopathy - Examination

Answer 3

Examination:

• General obs: signs of autoimmune disease (rash, other skin changes, joint deformity, etc)
• MSK exam to assess affected muscles/joints, screen for arthropathy, including tone, power ROM, functional status
• Neurological exam: assess power, screen for deficits indicative of alternative diagnosis

Question 4

Statin induced myopathy - Investigations

Answer 4

Investigations:
This would largely be a clinical diagnosis of exclusion, based on temporal relationship between statin use and symptoms, but would need to rule out other rheumatological conditions
- Bedside: Vitals, anthropogenic measurements
- Bloods: ESR/CRP, ANA/ENA, FBC, RF, anti-CCP, UEC, urinary myoglobin (rhabdo), lipid panel, HMG-CoA reductase antibody level (specific), creatinine-kinase given weakness, anti-HMGCR (high sensitivity for risk of statin induced myopathy)
- Imaging: X-Ray, CT if concerned
- Other: muscle biopsy, electromyography (EMG) (consideration for rheumatological inflammatory muscular conditions)

Question 5

Stating induced myopathy - Management

Answer 5

Management:
Mainstay of treatment would be to initiate a medications review with the intention of ceasing the statin, but concomitantly managing cardiovascular disease risk appropriately, both non-pharm and pharmacologically.

Pharmacological:

• cease statin, convert to other lipid-lowering medication
• correct reversible causes:
• rheum consult to consider starting immunosuppressive therapy, particularly if persistent sx despite ceasing statin
• consider starting alternative lipid-lowering medication (altho evidence demonstrates not effective at lowering mortality risk)
• PMR: 15mg Pred for 4 weeks then slow wean

Non-pharm

• diet -> weight loss
• exercise
• physiotherapy
• OT
• ongoing review