What are the potential causes and necessary investigations for a 35-year-old female (G3P3) with a month of numbness in her feet and groin area, without pain or swelling, and a glucose level of 5.3 mmol/L, who works in janitorial services?

Causes and Investigations for Peripheral Neuropathy in a 35-Year-Old Female

A comprehensive evaluation for peripheral neuropathy with numbness in the feet and groin area in a young female without diabetes should focus on metabolic, toxic, inflammatory, and nutritional causes, with diabetes still requiring exclusion despite normal glucose levels. 1

Clinical Presentation Assessment

Key Features in This Case

• 35-year-old female (G3P3)
• Numbness in feet and groin area for one month
• No swelling or pain
• Janitorial work (potential exposure to cleaning chemicals/toxins)
• Normal glucose level (5.3 mmol/L)
• No trauma, family history, smoking, or alcohol use

Anatomical Pattern Considerations

• Distribution suggests possible distal symmetric polyneuropathy (feet) with additional involvement of the groin area
• Groin area numbness raises concern for:
  • Possible lumbosacral radiculopathy
  • Meralgia paresthetica (lateral femoral cutaneous nerve entrapment)
  • Early presentation of a more widespread neuropathic process

Potential Causes of Peripheral Neuropathy

Metabolic/Endocrine Causes

• Prediabetes: Despite normal fasting glucose (5.3 mmol/L), consider glucose tolerance testing 2
• Hypothyroidism: Common treatable cause 3
• Vitamin B12 deficiency: Essential to exclude 1

Toxic/Environmental Causes

• Occupational exposure: Cleaning agents/solvents (relevant given janitorial work) 1
• Medication-induced neuropathy: Review all medications 3

Inflammatory/Immune Causes

• Chronic inflammatory demyelinating polyneuropathy (CIDP) 1
• Guillain-Barré syndrome: Less likely given one-month duration without progression 4
• Vasculitis 5

Other Causes

• Nutritional deficiencies: B-vitamins, vitamin E, copper 3
• Compression neuropathies: Particularly for groin symptoms 4
• Hereditary neuropathies: Despite no family history, some may present in adulthood 4

Recommended Investigations

Initial Laboratory Tests

1. Complete blood count: To assess for anemia, infection, inflammation 1
2. Comprehensive metabolic profile: Liver, kidney function 1
3. Fasting blood glucose and HbA1c: To confirm absence of diabetes 1
4. Oral glucose tolerance test: To evaluate for prediabetes despite normal fasting glucose 2
5. Thyroid function tests: TSH, free T4 1
6. Vitamin B12 level: Essential for all neuropathy evaluations 1
7. Serum protein electrophoresis with immunofixation: To evaluate for paraproteinemias 1
8. Erythrocyte sedimentation rate: To screen for inflammatory conditions 3

Additional Tests Based on Initial Results

• Autoimmune panel: ANA, RF, anti-SSA/SSB if inflammatory markers elevated
• Heavy metal screening: Particularly if occupational exposure suspected
• Vitamin E and copper levels: If nutritional deficiency suspected

Neurophysiological Testing

• Nerve conduction studies and electromyography: To differentiate between axonal and demyelinating neuropathy and assess severity 5
• Quantitative sensory testing: To evaluate small fiber function 5

Advanced Investigations if Initial Workup Inconclusive

• Lumbar puncture: If CIDP or other inflammatory neuropathy suspected 1
• MRI of lumbosacral spine: To evaluate for radiculopathy if groin symptoms predominate 6
• Skin biopsy for intraepidermal nerve fiber density: To assess for small fiber neuropathy 5
• Nerve biopsy: Reserved for cases that remain undiagnosed after extensive testing 1

Clinical Examination Focus

• Small-fiber function assessment: Pinprick and temperature sensation 5
• Large-fiber function assessment: Vibration sensation using 128-Hz tuning fork, lower-extremity reflexes 5
• Protective sensation: 10-g monofilament testing 5
• Vascular assessment: Pulses in legs and feet, capillary refill time 5
• Specific testing for groin numbness: Sensory mapping of affected area, evaluation for trigger points

Management Approach

Management will depend on the identified cause, but may include:

1. Correction of underlying cause: Nutritional supplementation, thyroid hormone replacement, removal of toxic exposure 3
2. Symptomatic treatment if needed:
   • First-line: Gabapentinoids, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants 5
   • Avoid opioids for neuropathic pain 5

Key Pitfalls to Avoid

• Assuming diabetes is ruled out based solely on a normal fasting glucose
• Missing occupational toxic exposures in janitorial work
• Overlooking compression neuropathies that might explain groin symptoms
• Failing to consider prediabetes as a potential cause of neuropathy despite normal fasting glucose

The unusual distribution of symptoms (feet and groin) warrants thorough investigation as it may represent either multiple pathologies or an atypical presentation of a single process.