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 fact that pain is not limited to joints but also involves thighs and shoulders support this diagnosis. The normal neuro exam and clean imaging studies also point towards a diagnosis that doesn't involve structural neurological damage.
• 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 and its potential for causing neuropathic pain should be considered.
  • 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 spasms, and fatigue. The rash mentioned could be related to lupus or another autoimmune condition.
  • Vitamin D Deficiency: Although the initial low level of Vitamin D was noted, its current status is not provided. Vitamin D deficiency can cause muscle pain, weakness, and fatigue, which are present in this patient.
• Do Not Miss Diagnoses
  • Multiple Sclerosis (MS): Despite clean brain and spine MRIs, MS can sometimes present with subtle or non-specific findings on imaging, especially in early stages. The visual processing issues, numbness, and muscle spasms could be indicative of MS. The brisk but symmetrical knee reflexes might also suggest a neurological condition.
  • Lyme Disease: Although testing was negative, the presence of a rash and the sudden onset of symptoms could still suggest Lyme disease, particularly if the patient has been exposed to ticks. Lyme disease can cause a wide range of neurological and musculoskeletal symptoms.
• Rare Diagnoses
  • Adrenoleukodystrophy (ALD): The elevated level of hexacosanoic acid (C26:0) is a marker for ALD, a rare genetic disorder that affects the brain and spinal cord, leading to progressive damage of the myelin sheath. It can present with a variety of symptoms including muscle spasms, visual disturbances, and fatigue. However, ALD typically presents in childhood, making this a less likely diagnosis unless the patient is a female carrier with a milder form of the disease.
  • Mitochondrial Myopathies: These are a group of disorders caused by mutations in the mitochondria, affecting muscle and nerve cells. They can present with muscle pain, weakness, and fatigue, among other symptoms. The slow visual processing could be related to a mitochondrial disorder affecting the brain and muscles.