DERMATOMYOSITISDermatomyositis and polymyositis = inflammatory myopathies that are often discussed together because they often present as symmetric proximal muscle weakness.
Dermatomyositis, however, is associated with skin findings and is much more likely to be associated with an underlying malignancy.
SKIN FINDINGS - Heliotrope rash (see picture),Gottron's papules, periungual changes, "mechanic's hands", and the shawl sign - which some MDs felt appeared more like a poncho sign in certain patients.
Lung Involvement - ILD, respiratory muscle weakness
GI Involvement - Dysphagia, regurgitation, aspiration
Cardiac Involvement - Myocarditis, pericarditis, arrhythmias
SEROLOGY - ANA+ in 80%. Ongoing research into myositis specific antibodies (currently felt to be present in 30%) to help determine likely clinical progression and treatment response
MALIGNANCY - Incidence of cancer is 5-7x higher than general pop'n. Peak incidence of diagnosis is within 2 years before or after the DM diagnosis. Search guided by complete history and physical. Bloodwork, imaging and tumor markers (CA125, CA 19-9, PSA) and age appropriate cancer screening.
Ongoing cancer surveillance suggested for 3-4 years after diagnosis or recurrence, with the exception of ovarian CA which can occur >5 years after diagnosis (therefore screen for longer).
Publications on malignancy frequency in DM/PM can be found here (don't forget they have a higher baseline incidence of nasopharyngeal CA in China - it isn't the most common DM associated cancer here) and here.
THERAPY- Treat the cancer!! (If you can find it without going overboard looking!)
Involves steroids at relatively high doese for prolonged periods of time. Steroid sparing agents such as azathipone and methotrexate are also used. Guided by clinical exam/weakness rather than CK/other markers.
As steroid course will be prolonged, be sure to consider the associated side effects and posible infections including TB.
Patients with polymyositis/dermatomyositis who have interstitial pulmonary fibrosis may be at increased risk for PCP with glucocorticoids alone compared to other populations.
A review of treatment can be found here.
