Introduction
Name the 4 of the 6 types of idiopathic inflammatory myopathies
Dermatomyositis, polymyositis, immune-mediated necrotizing myopathy, inclusion body myositis, overlap CTDs, and antisynthetase syndrome
What is the best imaging technique to identify muscle inflammation.
MRI
What do the skin biopsies show in patients with DM
Interface dermatitis similar to SLE patients
True or False: All IIMs are treated up front with glucocorticoids
False: IBM is unresponsive to anti-inflammatory and immunosuppressive treatment, though all other forms are and would be started on steroids.
ANA is present in 60 or 80% of DM/PM myositis patients.
Up to 60%
Name 2 clinical manifestations that all IIMs have in common
progressive muscle weakness and histopathologic findings of inflammatory infiltrates
They differ in specific biopsy findings, serologic abnormalities, prognosis, treatment, and weakness distribution
Name all 5 muscle-derived enzymes that can be abnormal in IIMs
CK, LDH, aldolase, AST, and ALT
Perivascular inflammation with predominately B-cells with smaller number of CD4-positive T-cells accumulated around blood vessels. Tend to see perifascicular atrophy and vasculitis.
Dermatomyositis
Along with steroids, what treatment can hasten recovery and in what two clinical scenarios is it used?
IVIG and used in severe disease and dysphagia
Name the two antibodies that are associated with IMNM
anti-SRP and HMGCR
True or False: Normal muscle enzymes rule out myositis
False, there are amyopathic subtypes. In DM this is referred to as having CADM or clinically amyopathic DM
True or False: A muscle biopsy is required to diagnose IIMs
False, if presentation is classic particularly in DM and IMNM; biopsy is not required. Though lack of cutaneous manifestations would require a biopsy to confirm.
Endomysial inflammatory infiltrate with predominately CD8 positive T cells
Polymyositis
How long should initial dose prednisone be continued prior to taper.
Until CK normalizes and weakness starts to improve, usually around 4 weeks.
Name 3 antibodies that if present can suggest overlap syndrome
SSA, SM, RNP, scleroderma specific (PM-Scl & Ku)
Most common IIM in patients over 50 years old
Inclusion body myositis
Name the characteristic EMG finding that can support a diagnosis of IIM
Presence of fibrillation potentials. Can also be seen in infectious, toxic, and metabolic myopathies. SN 85 SP 33
This complex is not normally found in normal muscle but can be isolated from myositis muscle biopsies and is thought to play a role in pathogenesis.
Class I Major Histocompatibility Complex
For pts with DM and skin findings, what two treatments can be considered that are skin specific treatments that will not benefit muscle involvement.
Photoprotection and hydroxychloroquine
Name the antibody that is associated with acute onset of DM, traditional shawl or V-sign, and may respond well to therapy.
anti-Mi-2, the antibody may also correlate with disease severity and normalize with disease remission. Low risk of malignancy.
Name a few diseases that should be included in your differential when assessing for muscle weakness
What instructions are important to include when asking for a muscle biopsy to ensure a good sample. Name at least 3.
Biopsy location - Newest area of weakness or determined by imaging
Do not use the side that underwent EMG
Do not use electrocautery to cut or place in formalin
Sample should be at least 2cm
The muscle should be kept moist in saline gauze and not submerged
Muscle should be taken to pathology within 30 minutes for best results
List pathologic features of IBM on muscle biopsy
Endomysial inflammation due to CD8+ T cells invading nonnecrotic fibers that contain rimmed vacuoles as well as mitochondrial abnormalities including ragged red fibers
At what time would you consider tapering off glucocorticoid-sparing agent and which of the 5 subtypes tend to fail treatment discontinuation.
In TIF-1gamma PM/DM which clinical feature if present further strengthens suspicion for malignancy.
Not thinking of malignancy specific symptoms like weight loss and pain.
Ovoid palatal patch; Other TIF features can include palmar hyperkeratotic papules, psoriasis-like lesions, and hypopigmented and telangiectasia patches