Dermatomyositis/Polymyositis Flashcards
Dermatomyositis/Polymyositis - P (3)
- Most important = Pruritis: often debilitating, major impact on QOL → impact on sleep***
- Muscle pain (myositis), weakness (often proximal) → impacts on mobility, falls risk***
- Rash: pink, violaceous
- Gottron’s papules: papules over knuckles (MCP, PIP, DIPs)
- Gottron’s sign: macular rash + erythema over elbows/knees
- Heliotrope rash: erythema -periorbital
- Pink-violaceous Rash over sun-exposed areas: V of the neck, shoulder, ULs, scalp
Dermatomyositis/Polymyositis investigations?
T:
- Elevated CK + aldolase** (disease activity)
- Auto-antibodies (Jo1, Mi2, Ku, PM-Scl, SRP)
- EMG: to exclude neuropathy. low amplitude MUP (motor unit potential) + spontaneous fibrillations
- Biopsy (nearly all needs it) + sometimes need MRI to guide biopsy area.
E:
- 10-15% will have associated cancer
- Is this paraneoplastic? do a paraneoplastic, anti-neuronal Abs
- Exclude cancer: e.g. CT CAP
- If no evidence, close surveillance (often present within 2 years)
What is your approach to the Management of dermatomyositis/polymyositis?
Confirm Dx:
- Muscle biopsy (cellular infiltrates), CK, CK-MB, Aldolase, auto-Ab titre (e.g. Jo1)
Associations:
- Screen for depression, social isolation (given debilitating pruritus, appearance problems)
Screen complications:
- ILD - PFT, 6MWT, HRCT
- Oesophageal: Speech path assessment, Oesophageal manometry (dysphagia)
- Cardiac: ECG (conduction, arrhythmia, ischaemia), troponin, TTE
- Malignancy: cancer screening, CTCAP if indicated
Goals:
- Screen/treat complications
- Improve QOL
Principles:
- Exclude + monitor for cancer
- Aggressive photoprotection
- Anti-pruritic
- Topical steroids + topical CNIs
- Systemic therapy
Non-pharm:
- Cutaneous manifestations
- Avoid sun-exposure**** (even little can be detrimental)
- Sunscreen with SPF ≥30 - every 3-4 hours***
- Vitamin D supplementation due to above
- Camphor oil (anti-pruritic)
- Myopathy
- Exercise - strength + aerobic exercise. If chair-bound still can do passive range of motion exercise to minimize contractures → then progress to isometric/resistive exercise
- Aspiration risk: speech pathology, modified diet
- Osteoporosis, Infection prophylaxis as usual given long-term steroids
Pharm: (most needs systemic treatments)
- Topical
- Steroids - use coverage of the site of cream (e.g. dressings/bandages) → increases penetration + potency.
- Give steroids break to minimize systemic side effects (can still get them!) - e.g. 2 weeks on, 2 weeks off
- Intralesional steroids (often impractical as rash is often extensive)
- Topical CNI as asteroids sparing agent (0.1% tacrolimus)
- Systemic
- Anti-histamines (must be sedating, non-sedating ones are not beneficial) - doxepin, amitriptyline, gabapentine
- Hydroxychloroquine - for mild, MTX - for severe as 1st therapy (or both)
- Systemic steroids
- Resistant or recurrent disease: AZA, MMF, IVIG, Rituximab, Tacrolimus, Cyclophosphamide
How would you assess disease activity in dermatomyositis? (3)
Clinical: CDASI - Cutaneous dermatomyositis disease area and severity index
Biochemical: CK and aldolase
How would you assess disease activity in polymyositis? (2)
- Clinical: regular assessment of muscle strength, especially proximal muscle groups
- Biochemical: CK
What is the value of testing for myositis-specific autoantibodies? Give examples (5-6 level)
Useful in assessing disease
- Prognosis: Jo-1 (anti-synthetase syndrome - ILD) - worse prognosis, influences tx (can’t use MTX), Mi-2 (good prognosis)
- Severity: Mi-2 (florid, fulminant onset, but good prognosis), SRP (fulminant disease)
- Predict disease course in future
The typical duration of systemic glucocorticoid for initial polymyositis?
Initially high-dose 1mg/kg prednisolone or pulse methylpred (1g/d for 3 days)
Remain high dose for few months
Total treatment last 9-12 months
So monitoring for steroids complication is a big topic for the long case.
Non-pharmacological Mx of Polymyositis? (or any inflammatory myopathy in general)
Clinical features of anti-synthetase syndrome? (5)
- Myositis
- ILD
- Mechanic’s hands
- Non-erosive arthritis
- Raynauds
How biopsy findings differ among different types of myositis?
Both DM and PM: muscle fibre necrosis, degeneration, regeneration and inflammatory cell infiltrates.
- DM: cellular infiltrate peri-fascicular & peri-vascular. B-cells and plasma-cytoid dendritic cells.
- PM: infiltrate is within the fascicle. CD8+ T cells.
- Mitochondrial myopathy: “red ragged fibre” diseases. EM shows increased no of enlarged abnormally shaped mitochondria.
- Necrotizing autoimmune myopathy - Links: paraneoplastic or statin-associated. Rare. Sometimes anti-SRP Abs present or anti-HMGCR auto antibodies (in some patients who are on statins)
Scattered necrotic muscle fibres, no inflammatory cells, otherwise morphologically normal. Unlikel DM, there is no perifascicular atrophy.
DDx for myositis? (6)
DM
PM
IBM
Drug-induced (statins, HMG-CoA reductase Ab +ve)
Paraneoplastic
Mitochondrial
What are extra-cutaneous/muscle manifestations of DM/PM? (4)
- Interstitial Lung Disease*** (anti-Jo1 + Anti-synthetase Ab +ve)
- Oesophageal - dysphagia + aspiration risk due to weakness of striated muscles in upper 1/3rd of oesophagus
- Cardiac - myocarditis - conduction, arrhythmia, CCF, MI (chronic inflammation)
- Malignancy
