A20 year old female has an erythematous rash over her face on both cheeks and across the bridge of her nose.This rash is made worse by sunlight exposure when she is outdoors. Along with the rash, she has had muscle and joint pain for several month. However, radiographs of the joints does not show any abnormalities, and she has normal joint mobility without deformity. Which of the following laboratory test findings is most characteristic of the disease-
A20 year old female has an erythematous rash over her face on both cheeks and across the bridge of her nose.This rash is made worse by sunlight exposure when she is outdoors. Along with the rash, she has had muscle and joint pain for several month. However, radiographs of the joints does not show any abnormalities, and she has normal joint mobility without deformity. Which of the following laboratory test findings is most characteristic of the disease-
💡 Explanation
**Core Concept**
The patient's symptoms, including an erythematous rash and joint pain, suggest a condition known as dermatomyositis, a type of inflammatory myopathy characterized by skin inflammation and muscle weakness. Dermatomyositis is an autoimmune disorder, where the immune system mistakenly attacks the body's own tissues.
**Why the Correct Answer is Right**
The characteristic laboratory finding in dermatomyositis is the presence of elevated creatine kinase (CK) levels, indicating muscle damage. This is because dermatomyositis involves the degeneration of muscle fibers, leading to the release of CK into the bloodstream. CK is an enzyme found in muscle tissue, and elevated levels are a hallmark of muscle damage. In dermatomyositis, the immune system attacks the muscle fibers, causing inflammation and damage, which leads to the release of CK.
**Why Each Wrong Option is Incorrect**
**Option A:** Elevated erythrocyte sedimentation rate (ESR) is a nonspecific finding that can be seen in many inflammatory conditions, including infections, autoimmune disorders, and malignancies. While ESR may be elevated in dermatomyositis, it is not a specific or characteristic finding.
**Option B:** Normal joint radiographs and mobility without deformity make rheumatoid arthritis (RA) less likely. RA typically involves joint damage and deformity, which is not present in this patient.
**Option C:** Elevated ANA (antinuclear antibody) levels are seen in various autoimmune disorders, including lupus and scleroderma. While ANA may be elevated in dermatomyositis, it is not a specific or characteristic finding.
**Option D:** Elevated liver enzymes are seen in various conditions, including liver disease and medications. While liver enzymes may be elevated in dermatomyositis, it is not a specific or characteristic finding.
**Clinical Pearl / High-Yield Fact**
Dermatomyositis is often associated with malignancies, particularly ovarian and lung cancer. A thorough cancer screening should be performed in patients with dermatomyositis.