Question

50-year-old woman has symmetrical, proximal muscle weakness for 6 months. On exam she has 4/5 motor strength in all extremities. A deltoid biopsy shows a lymphocytic infiltrate with focal necrosis of the muscle fibers. Her antinuclear antibody test is negative. Which of the following additional findings would be most likely to be present in the patient?

a) Elevated serum creatine kinase levels
b) Positive anti-Jo-1 antibody
c) Positive anti-centromere antibody
d) Positive anti-SSA/Ro antibody

Answer 1

a) Elevated serum creatine kinase levels

In a patient with symmetrical, proximal muscle weakness and biopsy showing muscle fiber necrosis, the most likely additional finding would be elevated serum creatine kinase levels, indicating muscle damage.

Step-by-step explanation:

A 50-year-old woman with symmetrical, proximal muscle weakness and a deltoid biopsy showing lymphocytic infiltrate with focal necrosis likely has an inflammatory myopathy.

With her antinuclear antibody (ANA) test being negative, a common additional finding would be elevated serum creatine kinase levels, which is a diagnostic indicator of muscle damage and is typically elevated in conditions like polymyositis and dermatomyositis.

Autoantibodies such as anti-Jo-1 are also associated with these conditions, especially in the presence of interstitial lung disease. However, since only one choice is appropriate and considering the provided options, elevated serum creatine kinase levels would be the most likely additional finding in this patient.