Differential Diagnosis

The patient's presentation of extreme sensitivity to the top of the right foot with sharp shooting pains, along with the appearance of small bumps that can be scratched off, suggests a multifactorial etiology. The history of lumbar degeneration is also a crucial factor to consider. Here's a categorized differential diagnosis:

• Single most likely diagnosis
  • Peripheral Neuropathy: Given the patient's history of lumbar degeneration, peripheral neuropathy is a plausible diagnosis. The sharp shooting pains could be indicative of nerve damage or irritation, possibly stemming from the lumbar spine issues. The sensitivity on the top of the foot could be related to neuropathic changes affecting the nerves supplying that area.
• Other Likely diagnoses
  • Morton's Neuroma: This condition involves a thickening of the tissue around the nerves leading to the toes, which can cause sharp, shooting pain in the foot. It's possible that the patient's symptoms are related to a neuroma, especially if the pain is localized between the toes.
  • Dysesthetic Pain: This is a type of chronic pain that can occur in patients with nerve damage or neuropathy. The patient's description of sharp shooting pains could be consistent with dysesthetic pain, particularly if it's related to the lumbar degeneration.
  • Contact Dermatitis or Irritant Dermatitis: The small bumps on the top of the foot that can be scratched off might suggest a skin reaction. If these bumps are indeed related to the patient's symptoms, a dermatological condition such as contact dermatitis could be a contributing factor.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Deep Vein Thrombosis (DVT): Although less likely, DVT should be considered, especially if the patient has risk factors such as recent immobilization or surgery. The pain and sensitivity could potentially be symptoms of a DVT, which is a medical emergency.
  • Infection (e.g., Cellulitis or Abscess): An infectious process could cause pain, sensitivity, and skin lesions. It's crucial to rule out an infection, as it would require prompt antibiotic treatment.
• Rare diagnoses
  • Erythromelalgia: A rare disorder characterized by burning pain, heat, and redness in the hands and feet. While less common, it could be considered if other diagnoses are ruled out.
  • Complex Regional Pain Syndrome (CRPS): A chronic pain condition that can cause severe, burning pain in the affected limb. It's a rare but possible diagnosis to consider if the patient's symptoms are severe and not explained by other conditions.