|
cutaneous manifestations:
| • | the primary, classic skin lesion is violaceous macular erythema distributed symmetrically |
| • | photosensitivity --> shawl sign |
| • | periungual telangiectasia |
| • | two distinct cutaneous lesions: |
| • | heliotrope = a type of plant with purplish colored flowers rash – violaceous slightly edematous periorbital patches that primarily involve the eyelids (eyelid edema may be an early and dramatic sign and may mimic angioedema or contact dermatitis) |
| • | Gottron’s papules – over the bony prominences |
muscular signs:
| • | muscle pain common in acute form |
| • | no correlation between extent of skin disease and myositis activity |
muscle enzymes:
| • | check CK, SGOT, ALT, AST, LDH, aldolase |
| • | MM subtype specific to skeletal muscle |
| • | not specific to myositis (exercise, trauma) |
| • | may be elevated in healthy african american males |
| • | used to follow clinical course in DM/PM; fluctuations correlate with clinical disease status (but may precede or follow change in clinical course by months) |
|
serology:
| • | myositis specific antibodies (MSA): |
| • | directed against cytoplasmic proteins and RNA |
| • | correlate with disease activity |
| • | Jo-1 – associated with pulmonary fibrosis |
diagnosis and ddx:
| • | biopsy proximal muscle (MRI can decrease sampling error) |
| • | EMG – distinguish neurogenic from myogenic process |
| • | vs. SLE – increase ANA, and less pruritis in SLE; malar eminences rather than periorbital area; between joints rather than Gottron’s papules; rash more red or pink (vs. violaceous) |
| • | biopsy of DM rash shows C5-9 membrane attack complexes, SLE not |
cancer – bronchial, colonic, and breast CA (25% of adult dermatomyositis cases???)
| • | PO steroids (issue: steroid myopathy (with long term PO) vs. worsening DM) |
| • | steroid myopathy – selective atrophy of type II muscle fibers |
| • | worsening DM – reduction of neck flexor strength is usually seen in natural progression of disease |
| • | trial increase of prednisone may be diagnostic |
| • | methotrexate – can use 1 to 3mg of daily folic acid to minimize side effects without sacrificing efficacy |
| • | azathioprine – screen patients for thiopurine methyltransferase deficiency |
| • | hydroxychloroquine – treats rash only (200mg BID) |
| • | IVIg – probably works secondary to decrease complement deposition secondary to blockade of Fc receptor in vascular walls (and decreased regulation of immunoglobulin production) |
|
juvenile dermatomyositis:
| • | similar skin lesions except increased calcinosis cutis (associated with disease duration and activity) |
| • | symmetric arthritis in large and small joints |
| • | no associated malignancy |
amyopathic dermatomyositis:
| • | 5 to 10% of patients with dermatomyositis |
| • | skin changes can precede systemic symptoms by years (1/3 present with only skin; usually <2 years before weakness develops) |
| • | defined as confirmed amyopathic DM with negative tests and persistent rash X 2 years |
| • | (6 months to 2 years = “provisional DM”) |
|
