JDM Flashcards
Which HLA allele was found to be a major immunogenetic risk factor?
HLA DRB1*0301 allele
Pathogenesis of JDM
PDCS circulate in the blood and upon activation by viral infection, upregulate CCR7 —> migrate to lymphoid tissues
- Cells recognize viruses through TLR9–> induce maturation of DCs—> activation of T cells
- pDCs also produce Type I IFN
- Can also see overexpression of MHC class I molecules
- Increased expression of CXCL9, CXCL10 and CXCL11
- Type I IFN also enhances auto antibody formation and B cell proliferation
- ENdothelial cells produce IL-1, VCAM-1 and other adhesion molecules
Bohan and Peter criteria
Presence of pathognomonic rash (heliotrope and Gottron papule) and 3 of the following 4 features
- Proximal muscle weakness
- elevated inflammatory markers
- EMG changes of chronic inflammatory myositis
- Histo patty changes of inflammatory myositis
Anti-p155/140
TIF-1 gamma
- Severe cutaneous disease
- Greater muscle weakness
- Lipodystrophy, skin ulceration, edema
- In adults, strong association with malignancy
Anti-MJ
NXP2
- Younger onset at disease onset
- Calcinosis
- Greater degree of muscle weakness
Predicts poor prognosis; frequent muscle cramps, atrophy, joint contractors, and dysphonia, GI ulcerations and bleeding
Anti-MDA5
Rapidly progressive ILD
Higher IL 18, 1L-6 and ferritin;
Fever and milder muscle disease (low CK levels)
Amyopathic
Anti-SAE
Initially Amyopathic disease in adult DM
Anti-Jo1 (Anti-ARS)
Antisynthetase syndrome;
Fever, ILD, RP, mechanics hands, non erosive arthritis,
- Better prognosis compared to anti Jo negative
Anti-SRP
Severe symmetrical muscle weakness, RP, very high CK levels, cardiac disease, dysphagia, ILD
- Older age, insidious onset
- Found more in JPM
Anti Mi
Cutaneous features, better prognosis
- Milder muscle, decreased risk of ILD, malignancy, responds well to standard therapies
EMG findings associated with JDM
- Increased spontaneous and insertional activity
- Low amp, short duration, polyphasic motor unit action potentials and early recruitment
Muscle biopsy
Perifascicular atrophy Muscle fiber size variation Muscle degeneration and regeneration centralization of the nuclei Vasculopathy swelling of the capillary endothelium and perivascular infiltration of pdcs, B and T cells and macrophages
Staining of MXA may correlate with disease activity
Amyopathic Dermatomyositis
Patients with characteristic rash without evidence of muscle involvement
- Milder disease
- Less frequent myalgia, arthritis, contractors, calcinosis, dysphagia, abdominal pain and fatigue
Juvenile Polymyositis
- Older age
- More severe muscle weakness
- higher CK level
- Frequent falls, RP, dyspnea, cardiac abnormalities
- Histo path shows mixed area of necrosis and regenerative muscle fibers, CD8T cells and macrophages
- Scattered as opposed to focal (JDM) as well as absence of vasculopathy
Most common malignancies associated with IIM
leukemia
lymphoma
CNS tumors
