What is the most likely diagnosis for a patient presenting with multiple eurythmic ulcerations, excoriation-related lesions, formication, significant hypertension, pupillary dilation, tachycardia, mild psychomotor agitation, and tremor?

Stimulant Use Disorder

This patient's presentation is most consistent with stimulant use disorder, specifically methamphetamine or cocaine use, characterized by the classic triad of formication ("invisible spider bites"), sympathomimetic toxidrome (hypertension, tachycardia, pupillary dilation, psychomotor agitation), and chronic use stigmata (poor dentition, emaciation, excoriation lesions). 1, 2

Clinical Presentation Analysis

Sympathomimetic Toxidrome Features

• Cardiovascular manifestations include significant hypertension and tachycardia, which are hallmark features of stimulant intoxication 3, 1
• Pupillary dilation (mydriasis) is a specific finding consistent with sympathomimetic drug exposure, distinguishing this from other toxidromes 3
• Psychomotor agitation and tremor reflect the acute psychostimulatory effects of methamphetamine or cocaine on monoaminergic systems 2

Pathognomonic Dermatologic Findings

• Formication ("invisible spiders") represents tactile hallucinations characteristic of stimulant-induced psychosis, where patients experience crawling sensations under the skin 1, 2
• Multiple excoriation-related lesions (2-3 cm superficial) result from compulsive scratching in response to formication, creating self-inflicted wounds at various healing stages 2
• Eurythmic ulcerations on bilateral extremities reflect chronic picking behavior and poor wound healing associated with stimulant use 1

Chronic Stimulant Use Stigmata

• Poor dentition ("meth mouth") results from xerostomia, bruxism, poor oral hygiene, and direct toxic effects of stimulants on dental structures 2
• Emaciation reflects the anorexigenic effects of chronic stimulant use, with significant weight loss and nutritional deficiency 1, 2

Differential Diagnosis Exclusion

Why Not Opioid Use Disorder

• Opioid intoxication produces miosis (pinpoint pupils), not mydriasis 3
• Opioids cause hypotension and bradycardia, not hypertension and tachycardia 3
• Opioid users do not typically present with formication or excoriation lesions 2

Why Not Scabies Infection

• Scabies produces visible burrows in web spaces, wrists, and genitalia, not the described ulcerations 3
• Scabies does not cause hypertension, tachycardia, pupillary dilation, or psychomotor agitation 3
• The patient's description of "invisible" organisms and chronic, recurrent nature contradicts scabies pathophysiology 3

Why Not Actual Spider Bites

• True spider bites are isolated events, not chronic recurrent lesions "happening all the time" 2
• Spider bites do not cause systemic sympathomimetic symptoms (hypertension, tachycardia, mydriasis) 3
• The bilateral distribution and various healing stages are inconsistent with arachnid envenomation 2

Diagnostic Workup

Immediate Laboratory Evaluation

• Urine drug screen for amphetamines, methamphetamine, and cocaine metabolites to confirm stimulant exposure 3
• Complete blood count to assess for anemia and thrombocytopenia 4
• Basic metabolic panel including creatinine, sodium, and potassium to evaluate for acute kidney injury and electrolyte disturbances 4
• Cardiac troponin to assess for myocardial injury, as stimulants cause significant cardiovascular toxicity 2

Physical Examination Priorities

• Fundoscopic examination to evaluate for hypertensive retinopathy (flame hemorrhages, cotton wool spots, papilledema) 4
• Cardiovascular assessment for arrhythmias and signs of acute coronary syndrome 2
• Neurological examination to exclude hypertensive encephalopathy or stroke 4

Management Algorithm

Acute Stabilization

• Blood pressure control with short-acting agents (labetalol or esmolol) if hypertensive emergency criteria are met (BP >180/120 mmHg with end-organ damage) 5
• Benzodiazepines (e.g., lorazepam 2-4 mg IV) for agitation, tremor, and potential seizure prophylaxis 3
• Avoid beta-blockers alone as they may cause unopposed alpha-adrenergic stimulation and paradoxical hypertension 5

Psychiatric and Addiction Medicine Consultation

• Cognitive behavioral therapy shows modest effectiveness for stimulant use disorder 1, 2
• Contingency management (behavioral reinforcement strategies) demonstrates the strongest evidence for treatment 2
• No FDA-approved pharmacotherapy currently exists for stimulant use disorder, though research into novel biological targets is ongoing 1, 2

Critical Clinical Pitfalls

Avoid Rapid Blood Pressure Reduction

• Excessive BP lowering can cause cerebral, myocardial, or renal underperfusion 4
• Target 25% reduction in first hour, then gradual normalization over 24-48 hours 5

Do Not Dismiss Cardiovascular Risk

• Stimulant use causes acute coronary syndrome, myocardial infarction, and cerebrovascular events even in young patients 2
• Early cardiovascular warning signs must be recognized to mitigate mortality 2

Recognize Serotonin Syndrome Risk

• Concurrent use of multiple serotonergic drugs (SSRIs, cocaine, amphetamines) can precipitate serotonin syndrome 3
• Classic triad includes clonus, hyperreflexia, and diaphoresis with autonomic instability 3