Differential Diagnosis

The patient's symptoms are complex and multifaceted, involving pain, stiffness, muscle spasms, visual processing issues, and fatigue. Given the information, the differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis

  • Fibromyalgia: This condition is characterized by widespread musculoskeletal pain accompanied by fatigue, sleep, memory, and mood issues. The patient's description of burning/squeezing/achey pain, increased sensitivity to stimuli, and varying intensity of pain aligns with fibromyalgia. The presence of fatigue, muscle spasms, and the pattern of pain distribution also support this diagnosis.

• Other Likely Diagnoses

  • Peripheral Neuropathy: Despite clean EMG/NCV tests, the symptoms of numbness/pins and needles, especially with stimulus, could suggest a form of neuropathy. The very low initial vitamin D level could be a contributing factor, as vitamin D deficiency is known to cause neuropathic pain.
  • Lupus or Other Connective Tissue Disease: The positive ANA at significant titers in the past, although decreasing, suggests an autoimmune component. Lupus can cause a wide range of symptoms including joint pain, muscle pain, and fatigue. The rash mentioned could be related to lupus or another autoimmune condition.
  • Vitamin D Deficiency: Although the initial vitamin D level was very low, and it's not clear if this has been adequately addressed, vitamin D deficiency can cause muscle pain, weakness, and fatigue.

• Do Not Miss Diagnoses

  • Multiple Sclerosis (MS): Despite clean brain and spine MRIs, MS can sometimes present with atypical symptoms and normal initial imaging. The visual processing issues, especially after exercise or heat, could suggest optic neuritis, a common presentation of MS. The presence of muscle spasms and stiffness also warrants consideration of MS.
  • Lyme Disease: Although testing was negative, the presence of a rash and the sudden onset of symptoms could suggest Lyme disease, particularly if the patient has been in an area where Lyme is common. Lyme can cause a wide range of neurological and musculoskeletal symptoms.
  • Mitochondrial Myopathies: The abnormal long-chain fatty acid level (hexacosanoic acid) could suggest a mitochondrial disorder. These conditions can cause muscle pain, weakness, and fatigue, among other symptoms.

• Rare Diagnoses

  • Erythromelalgia: Characterized by burning pain, heat, and redness in the hands and feet, though the patient's symptoms are more focused on the knees, thighs, and shoulders. It's a rare condition but could be considered given the burning pain description.
  • Complex Regional Pain Syndrome (CRPS): Typically presents with intense burning or aching pain in the hands or feet after an injury, but the patient's symptoms are more widespread and not clearly linked to an injury. However, the increased sensitivity to stimuli and the description of the pain could warrant consideration of CRPS in a broader sense.