What is the likely diagnosis and appropriate work‑up for a 35‑year‑old lumber‑yard worker with a one‑month history of bilateral hand and foot numbness, painful tingling, and a single white horizontal line (leukonychia striata) on each fingernail?

Arsenic Poisoning: Likely Diagnosis and Work-Up

This 35-year-old lumber yard worker presenting with bilateral hand and foot numbness, painful tingling, and single white horizontal lines on all fingernails (Mees' lines) most likely has arsenic poisoning from occupational exposure to arsenic-treated lumber.

Clinical Reasoning

The combination of peripheral neuropathy in a stocking-glove distribution plus Mees' lines (single white horizontal bands across all nails) is pathognomonic for heavy metal toxicity, particularly arsenic. The occupational context of lumber yard work is critical—arsenic-containing compounds (chromated copper arsenate) were historically used as wood preservatives and remain present in older treated lumber.

Key Diagnostic Features Present:

• Bilateral sensory neuropathy with painful tingling and numbness affecting hands and feet simultaneously
• Mees' lines (leukonychia striata)—single white horizontal nail bands appearing on ALL fingernails, which develop 4-6 weeks after acute arsenic exposure
• Occupational exposure to arsenic-treated lumber products

Why This Is NOT Chemotherapy-Induced Neuropathy:

While the provided guidelines extensively discuss chemotherapy-induced peripheral neuropathy 1, 2, 1, these are irrelevant to this patient who has no cancer history. The nail findings also differ—taxane-induced onycholysis presents as nail separation and lifting 3, not horizontal white bands.

Why This Is NOT Vibration-Related:

Although lumber workers may use vibratory tools 4, 5, vibration-induced neuropathy typically presents asymmetrically with predominant vascular symptoms (white finger phenomenon) rather than symmetric sensory neuropathy with nail changes.

Immediate Work-Up Required

Laboratory Testing (Priority Order):

1. 24-hour urine arsenic level (most sensitive for recent exposure)
2. Blood arsenic level (useful for acute poisoning)
3. Hair and nail arsenic analysis (documents chronic exposure)
4. Complete blood count with peripheral smear (look for basophilic stippling, anemia)
5. Comprehensive metabolic panel (assess liver and kidney function)
6. Nerve conduction studies if diagnosis unclear (will show axonal sensory neuropathy)

Clinical Assessment:

• Document exact sensory distribution using pinprick and light touch
• Test vibration sense with 128-Hz tuning fork
• Assess for motor weakness (less common but possible)
• Examine for other arsenic toxicity signs: hyperpigmentation, hyperkeratosis of palms/soles, gastrointestinal symptoms
• Photograph nail findings for documentation

Occupational History Details Needed:

• Duration and intensity of exposure to pressure-treated lumber
• Use of personal protective equipment
• Handling of sawdust from treated wood
• Burning of treated wood (releases arsenic vapor)
• Coworkers with similar symptoms

Management Approach

Immediate Actions:

1. Remove from exposure immediately—critical to prevent progression
2. Chelation therapy with DMSA (dimercaptosuccinic acid) or DMPS (dimercaptopropane sulfonate) if arsenic levels confirm poisoning and exposure was recent (within weeks)
3. Supportive care for neuropathic symptoms
4. Report to occupational health authorities—this is a reportable occupational disease

Symptomatic Treatment:

For neuropathic pain, duloxetine can be offered based on evidence for peripheral neuropathy management 1, 6, though the primary treatment is removing the toxic exposure.

Critical Pitfalls to Avoid

• Do NOT delay testing while waiting for symptom progression—arsenic neuropathy can become irreversible
• Do NOT assume this is carpal tunnel syndrome despite the occupation—bilateral symptoms with nail changes indicate systemic toxicity
• Do NOT order only blood arsenic—urine arsenic is more sensitive for subacute exposure
• Do NOT forget to assess other workers—this may represent a workplace hazard affecting multiple employees

Prognosis

With prompt diagnosis and removal from exposure, sensory symptoms may partially improve over months, though complete recovery is variable. The Mees' lines will grow out with the nail (approximately 6 months for complete resolution). Continued exposure will lead to progressive, potentially irreversible neuropathy with motor involvement and systemic toxicity affecting multiple organ systems.

The priority is confirming arsenic poisoning through urine testing and immediately removing the patient from further occupational exposure to prevent permanent neurological damage.