Differential Diagnosis for Feeling of Things Crawling with Anxiety

• Single most likely diagnosis:
  • Formication: This is a tactile hallucination that creates a sensation of ants or insects crawling on or under the skin, often associated with anxiety, substance abuse, or withdrawal. The feeling of things crawling is a hallmark symptom, making it the most likely diagnosis.
• Other Likely diagnoses:
  • Anxiety Disorder: Generalized anxiety, panic disorder, or social anxiety can cause significant distress and may include somatic symptoms like formication. The anxiety mentioned in the question could be a primary symptom of an underlying anxiety disorder.
  • Substance Withdrawal: Withdrawal from substances such as alcohol, benzodiazepines, or opioids can lead to formication and significant anxiety.
  • Delusional Parasitosis: A psychiatric condition where the person has a fixed, false belief that they are infested with parasites, which can cause significant anxiety and a sensation of things crawling on the skin.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Neurosyphilis: A late manifestation of syphilis infection that can cause a variety of neurological symptoms, including formication. Missing this diagnosis could lead to severe neurological damage or death if not treated promptly.
  • Vitamin B12 Deficiency: Severe deficiency can lead to neurological symptoms, including formication, and if left untreated, can result in permanent neurological damage.
  • Thyroid Disorders: Both hyperthyroidism and hypothyroidism can cause skin sensations and anxiety. Although less common, missing a thyroid disorder could lead to significant morbidity.
• Rare diagnoses:
  • Ekbom Syndrome: A rare condition also known as delusional parasitosis, where the patient has a delusional belief of being infested with parasites.
  • Pellagra: Caused by niacin deficiency, it can lead to dermatitis, diarrhea, dementia, and potentially death if not treated. Formication can be a symptom in the early stages.
  • Heavy Metal Poisoning: Exposure to heavy metals like mercury or arsenic can cause formication among other neurological and systemic symptoms.