A 58-year-old woman presents to your clinic with complaints of muscle weakness and fatigue over the past three months. She mentions having difficulty rising from a chair and combing her hair. She also notices a rash around her eyes that is purplish in color, and she has developed scaly lesions over the knuckles. Her creatine kinase (CK) levels are significantly elevated. On further evaluation, you suspect dermatomyositis.
Which of the following is most commonly associated with dermatomyositis?
A. Rheumatoid arthritis
B. SLE
C. Systemic sclerosis
D. Underlying malignancy
E. Polymyalgia rheumatica
Correct Answer: D. Underlying malignancy
Detailed Explanation:
Dermatomyositis is an inflammatory muscle disease that is often accompanied by skin manifestations, such as the heliotrope rash (a purplish rash around the eyes) and Gottron’s papules (raised, scaly lesions over the knuckles). One of the most important associations of dermatomyositis, especially in adults over 50, is its link to underlying malignancy. Around 10-30% of dermatomyositis cases are associated with cancers, including cancers of the ovary, lung, breast, and gastrointestinal tract. This association is known as the paraneoplastic syndrome, where dermatomyositis is considered an indicator of malignancy.
Key Features of Dermatomyositis:
- Proximal Muscle Weakness: Patients experience weakness in proximal muscles, especially in the shoulders and hips, leading to difficulty with activities like rising from a chair or combing their hair.
- Skin Findings:
- Heliotrope rash: A purplish rash around the eyelids.
- Gottron’s papules: Red or purple scaly lesions over the knuckles and elbows.
- Elevated Muscle Enzymes: Creatine kinase (CK) levels are typically elevated in dermatomyositis, reflecting muscle damage.
- Associated Malignancies: The presence of dermatomyositis in an older patient often prompts an investigation for underlying cancers, as the malignancy may predate or be diagnosed concurrently with dermatomyositis.
Why Other Options Are Incorrect:
A. Rheumatoid arthritis
While both rheumatoid arthritis and dermatomyositis are autoimmune diseases, they have different clinical presentations. Rheumatoid arthritis affects primarily the joints, whereas dermatomyositis affects muscles and skin. Rheumatoid arthritis is not commonly associated with dermatomyositis or malignancy.
B. SLE (Systemic Lupus Erythematosus)
SLE can involve the skin and cause systemic symptoms like dermatomyositis but is not as strongly linked to malignancy. In SLE, the most common skin manifestation is the malar rash (butterfly-shaped rash across the cheeks and nose), which is different from the heliotrope rash seen in dermatomyositis.
C. Systemic sclerosis (Scleroderma)
Systemic sclerosis primarily causes skin thickening and fibrosis and is associated with internal organ involvement such as lung and kidney disease. It does not have the same muscle weakness or rash profile seen in dermatomyositis. While both diseases may overlap in some patients, systemic sclerosis is not associated with malignancy in the same manner.
E. Polymyalgia rheumatica
Polymyalgia rheumatica presents with muscle pain and stiffness, particularly in the shoulders and hips, but it does not cause the characteristic skin changes or muscle weakness of dermatomyositis. Polymyalgia rheumatica is also not associated with underlying malignancy.
Treatment:
- Corticosteroids (e.g., prednisone) are typically the first-line treatment to reduce inflammation and improve muscle strength.
- Immunosuppressive medications like methotrexate, azathioprine, or mycophenolate mofetil may be used for patients with more severe disease or those resistant to steroids.
- Cancer screening: For patients over 50, or those with suspected paraneoplastic dermatomyositis, screening for underlying malignancy (e.g., breast, ovarian, lung cancers) is essential.