A 70-year-old woman is seen by her physician for evaluation of severe headaches. She noted these several weeks ago, and they have been getting worse. Although she has not had any visual aura but she has been intermittently losing vision in her left eye for the last few days. She denies new weakness or numbness, but she does repo jaw pain with eating. Her past medical history includes coronary aery disease requiring a bypass grafting 10 years prior, diabetes mellitus, hyperlipidaemia, and mild depression. Full review of symptoms is notable for night sweats and mild low back pain paicularly prominent in the morning. Which of the following is the next most appropriate step?

**Core Concept**
The patient's presentation of severe headaches, intermittent vision loss, jaw pain with eating, night sweats, and low back pain is suggestive of Giant Cell Arteritis (GCA), an inflammatory vasculitis affecting medium and large arteries.

**Why the Correct Answer is Right**
GCA typically affects older adults and can cause headaches, visual disturbances, jaw claudication (pain with eating), and systemic symptoms like night sweats and low back pain. The patient's risk factors, including age and a history of coronary artery disease, also support this diagnosis. A temporal artery biopsy is the gold standard for diagnosis but is often impractical due to its invasive nature. Therefore, imaging studies like MRI or CT angiography of the temporal arteries are used as a substitute.

**Why Each Wrong Option is Incorrect**
**Option A:** Ordering a lumbar puncture (LP) would not be the next step in this case, as it would be more appropriate for diagnosing conditions like meningitis, which is not suggested by this patient's presentation.
**Option B:** Performing an electrocardiogram (ECG) or echocardiogram would be more relevant for assessing cardiac function in the context of her coronary artery disease, but would not address the current symptoms.
**Option C:** Ordering a complete blood count (CBC) with differential may be useful in assessing inflammation, but would not be the next most appropriate step in diagnosing GCA.

**Clinical Pearl / High-Yield Fact**
GCA is often referred to as "temporal arteritis" due to its predilection for the temporal arteries, but it can affect other large and medium arteries as well. A high index of suspicion is crucial, especially in older adults with systemic symptoms.

**Correct Answer:** C.

✓ Correct Answer: C. Immediate initiation of glucocoicoid