Differential Diagnosis for Crawling Sensations on Feet

The patient presents with crawling sensations on feet that started during a small cold, low ferritin levels (27), and a slightly low white blood cell count (WBC) of 3.6, with other blood work being normal. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Iron Deficiency: The low ferritin level is a strong indicator of iron deficiency, which can cause neurological symptoms such as crawling sensations on the skin (formication) due to the role of iron in neurotransmitter synthesis and function.

• Other Likely Diagnoses

  • Vitamin B12 Deficiency: Although not directly indicated by the provided lab results, vitamin B12 deficiency can cause neurological symptoms including formication. It's worth considering, especially if the patient has a diet low in animal products or has conditions affecting B12 absorption.
  • Anxiety or Stress: The onset during a cold could be coincidental, and stress or anxiety from being ill might exacerbate or trigger symptoms of formication.
  • Hypothyroidism: While not directly linked to the provided lab results, hypothyroidism can cause skin sensations and should be considered, especially if other symptoms are present.

• Do Not Miss Diagnoses

  • Diabetic Neuropathy: Although the patient's blood work is mostly normal, diabetes can sometimes present with neuropathic symptoms before blood glucose levels are overtly abnormal. Missing this diagnosis could lead to significant morbidity.
  • Lymphoma or Leukemia: The low WBC count could be indicative of a bone marrow disorder. While less likely, these conditions are critical to diagnose early due to their potential severity and the importance of timely treatment.
  • Neurodegenerative Diseases: Rarely, conditions like Parkinson's disease or multiple sclerosis could present with formication, among other symptoms. These are crucial to identify due to their significant impact on the patient's quality of life and the availability of disease-modifying treatments.

• Rare Diagnoses

  • Pernicious Anemia: An autoimmune condition leading to vitamin B12 deficiency, which could explain formication if the patient has a deficiency in intrinsic factor or has undergone gastric surgery.
  • Erythromelalgia: A disorder characterized by burning pain, heat, and redness in the hands and feet, which could be considered if the crawling sensation is accompanied by these symptoms.
  • Certain Infections: Such as shingles or Lyme disease, which can cause skin sensations and should be considered based on exposure history and other symptoms.

Each of these diagnoses should be considered in the context of the patient's full medical history, physical examination, and potentially additional diagnostic testing to determine the underlying cause of the crawling sensations on their feet.