Differential Diagnosis
The patient presents with a 6-week history of generalized muscle pain, lack of appetite, significant weight loss, diffuse tenderness in the scalp and neck, and painless loss of vision in one eye. Considering these symptoms, the differential diagnosis can be organized into the following categories:
Single most likely diagnosis
- Giant Cell Arteritis (GCA): This condition is the most likely diagnosis given the patient's age, symptoms of scalp and neck tenderness, and painless loss of vision in one eye, which are classic presentations of GCA. The disease can lead to blindness in the other eye if not promptly treated.
Other Likely diagnoses
- Polymyalgia Rheumatica (PMR): This condition often co-exists with GCA and presents with muscle pain and stiffness, particularly in the shoulders and hips, which could explain the patient's generalized muscle pain.
- Temporal Arteritis: This is closely related to GCA and could explain the scalp tenderness and visual disturbances.
- Cancer: The significant weight loss and lack of appetite could suggest an underlying malignancy, although this would not directly explain the visual loss or scalp tenderness.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Stroke or Transient Ischemic Attack (TIA): Given the patient's scheduled ultrasonography of the carotid arteries, there is a concern for cerebrovascular disease, which could lead to stroke or TIA, potentially causing the visual loss and other symptoms.
- Vasculitis (other forms): Other types of vasculitis, such as ANCA-associated vasculitis, could present with similar symptoms and would require prompt diagnosis and treatment to prevent serious complications.
Rare diagnoses
- Amyloidosis: This condition can cause weight loss, muscle pain, and visual disturbances due to amyloid deposits in various tissues, including the eyes.
- Sarcoidosis: Although less likely, sarcoidosis can cause a wide range of symptoms including muscle pain, weight loss, and visual disturbances due to granulomatous inflammation in various parts of the body.
Given the patient's presentation, the greatest immediate risk appears to be related to the potential for further visual loss or other complications from Giant Cell Arteritis, making A) Blindness in the left eye a significant concern if the condition is not promptly diagnosed and treated.