Differential Diagnosis

Based on the symptoms described by your friend, including pain in the leg, feet, and right hand and arm, along with severe vomiting, here is a differential diagnosis organized into the requested categories:

• Single Most Likely Diagnosis
  • Peripheral Neuropathy or Radiculopathy: This could be a recurrence or exacerbation of a condition affecting the nerves, given the spread of pain to multiple limbs and the presence of vomiting, which might be related to pain or another underlying condition.
• Other Likely Diagnoses
  • Musculoskeletal Injury or Inflammation: Conditions such as tendinitis, bursitis, or even a systemic condition like rheumatoid arthritis could cause widespread pain, especially if the condition has progressed or if there are multiple sites of injury.
  • Infection: Certain infections, including those affecting the bone (osteomyelitis), joint (septic arthritis), or soft tissues (cellulitis, abscess), could cause localized pain and systemic symptoms like vomiting.
  • Vascular Issues: Conditions affecting blood flow, such as deep vein thrombosis (DVT) or peripheral artery disease, could cause limb pain, though the involvement of an arm and the presence of vomiting might suggest a more complex or systemic issue.
• Do Not Miss Diagnoses
  • Neurological Emergency (e.g., Stroke, Transverse Myelitis): Although less likely given the description, conditions like a stroke (if the vomiting and pain are accompanied by other neurological deficits) or transverse myelitis (inflammation of a segment of the spinal cord) are critical to rule out due to their potential for severe and permanent damage.
  • Sepsis: If the vomiting and pain are part of a systemic response to an infection, sepsis is a potentially life-threatening condition that must be considered and promptly treated.
  • Guillain-Barré Syndrome: An autoimmune disorder that can cause ascending paralysis and could potentially explain widespread pain and vomiting, especially if there's been a recent infection.
• Rare Diagnoses
  • Complex Regional Pain Syndrome (CRPS): A condition characterized by intense burning or aching pain in the hands or feet after an injury or trauma, which could potentially explain the pain but might not fully account for the vomiting.
  • Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues, which could lead to widespread pain and potentially other systemic symptoms.
  • Porphyria: A group of disorders that can cause abdominal pain, neurological symptoms, and psychological disturbances, which might fit some of the symptoms described but would be less common.

Each of these diagnoses requires careful consideration of the patient's full medical history, a thorough physical examination, and potentially, further diagnostic testing to determine the underlying cause of the symptoms.