Differential Diagnosis for Vision Changes, Pruritus, and Weakness

The patient's symptoms of vision changes, diffuse pruritus, burning sensation, and weakness with prolonged activity can be attributed to various conditions. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Multiple Sclerosis (MS): MS is a leading consideration due to the combination of vision changes (which could be optic neuritis), sensory symptoms like pruritus and burning sensations, and weakness that worsens with activity (a phenomenon known as Uthoff's phenomenon). MS is known for its unpredictable course and wide range of neurological symptoms.

• Other Likely Diagnoses

  • Vitamin B12 Deficiency: This condition can cause neurological symptoms including weakness, vision changes, and paresthesias (abnormal sensations such as burning). It's a treatable condition that should be considered, especially if the patient has a history of dietary deficiencies or malabsorption.
  • Diabetic Neuropathy: Although typically associated with long-standing diabetes, neuropathy can cause a variety of sensory symptoms including burning sensations and weakness. Vision changes could be related to diabetic retinopathy.
  • Thyroid Disorders: Both hypothyroidism and hyperthyroidism can cause a wide range of symptoms including weakness, skin changes (potentially leading to pruritus), and eye symptoms (such as dryness or vision changes in Graves' disease).

• Do Not Miss Diagnoses

  • Spinal Cord Compression: This is a medical emergency that can cause progressive weakness, sensory changes, and autonomic dysfunction. Prompt diagnosis and treatment are crucial to prevent permanent damage.
  • Cancer (e.g., Lymphoma, Leukemia): Certain cancers can cause a wide range of systemic and neurological symptoms, including pruritus and weakness. A diagnosis of cancer would significantly alter the management and prognosis.
  • Neurosyphilis: This condition can present with a variety of neurological symptoms, including vision changes, and should be considered, especially in patients with risk factors for syphilis.

• Rare Diagnoses

  • Tangier Disease: A rare genetic disorder that affects the nervous system and can cause weakness and sensory changes, among other symptoms.
  • Adrenomyeloneuropathy: A rare genetic disorder that affects the adrenal glands and spinal cord, leading to symptoms like weakness and sensory changes.
  • Mitochondrial Myopathies: A group of rare disorders that affect the mitochondria and can cause a variety of symptoms including weakness, especially with prolonged activity, and neurological symptoms.

Each of these diagnoses has the potential to explain some or all of the patient's symptoms, and a thorough diagnostic workup, including laboratory tests and imaging studies, would be necessary to determine the underlying cause.