# Clinical Cases: Occupational Medicine

## Case 1: Occupational Asbestosis

### Patient Presentation
**Demographics:** 67-year-old male retired shipyard insulation worker

**Chief Complaint:** "I've had a dry cough and shortness of breath that's been getting worse over the past 2 years."

**History of Present Illness:**
Mr. J.P. presents to the occupational medicine clinic referred by his primary care physician for progressive dyspnea on exertion and a persistent dry, non-productive cough. He reports that he first noticed exercise intolerance approximately 3 years ago when he could no longer walk 18 holes of golf without stopping to rest. Over the past year, he has become dyspneic walking one block on flat ground and can only climb one flight of stairs before needing to pause.

He worked as an insulation installer and pipe fitter at a naval shipyard from 1978 to 2003 (25 years). He reports heavy daily exposure to chrysotile and amosite asbestos during ship construction and repair, particularly during the 1980s when asbestos-containing materials were still widely used. Personal protective equipment was inconsistently provided and respiratory protection was limited to simple dust masks when available. He also reports bystander exposure from adjacent asbestos removal operations.

He denies hemoptysis, chest pain, weight loss, or night sweats. He has noted increasing fatigue and has reduced his activities significantly. He was seen by pulmonology 6 months ago and started on an inhaler with minimal improvement.

**Past Medical History:**
- Hypertension (well-controlled)
- Benign prostatic hyperplasia
- Bilateral knee osteoarthritis
- No prior lung disease diagnosis

**Medications:**
- Lisinopril 20 mg daily
- Tamsulosin 0.4 mg daily
- Tiotropium bromide 18 mcg inhaled daily
- Acetaminophen 500 mg PRN

**Social History:**
- Former smoker: 15 pack-year history (quit 1998)
- Married, 3 children
- Retired since 2003; previously active in home woodworking
- No current occupational exposures
- Moderate alcohol use (2-3 beers per week)

**Family History:**
- Father: died of myocardial infarction age 72
- Mother: alive, age 89, with dementia
- No family history of lung disease or malignancy

### Physical Examination
- **Vital Signs:** BP 132/78 mmHg, HR 88 bpm, RR 20, SpO2 92% on room air (89% with ambulation), Temp 36.6°C, BMI 26.8 kg/m²
- **General:** Thin-appearing elderly male, mildly tachypneic at rest
- **Chest/Pulmonary:** Bilateral end-inspiratory fine crackles ("velcro rales") at both lung bases, extending to mid-zones; no wheezing; diminished breath sounds at bases
- **Cardiovascular:** Regular rate and rhythm, prominent P2 (suggesting pulmonary hypertension), no peripheral edema
- **Extremities:** Digital clubbing present in all fingers (grade 3); no cyanosis at rest
- **Skin:** No rashes or lesions; no evidence of pleural plaques palpable on chest wall

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| CBC | WNL | - |
| ESR | 28 mm/hr | 0-22 mm/hr |
| ANA | Negative | Negative |
| RF | Negative | <14 IU/mL |
| BNP | 185 pg/mL | <100 pg/mL |
| LDH | 245 U/L | 140-280 U/L |
| Mesothelin (SMRP) | 1.2 nmol/L | <1.5 nmol/L |

**Imaging/Additional Studies:**
- **Chest X-ray:** Bilateral irregular opacities predominantly in lower zones (ILO classification: profusion 2/2, shape/size s/t); bilateral diaphragmatic calcified pleural plaques; blunting of costophrenic angles bilaterally
- **HRCT Chest:** Bilateral subpleural reticular opacities with honeycombing in lower lobes; traction bronchiectasis; ground-glass opacities at periphery of both lower lobes; bilateral calcified pleural plaques on diaphragmatic and posterolateral parietal pleura; no pleural effusion; no lung masses
- **Pulmonary Function Tests:** FVC 2.18 L (58% predicted), FEV1 1.92 L (68% predicted), FEV1/FVC ratio 0.88 (normal — restrictive pattern), DLCO 42% predicted (severely reduced), TLC 4.1 L (62% predicted)
- **6-Minute Walk Test:** Distance 285 m (predicted ~520 m); SpO2 decreased from 92% to 84% with exertion; Borg dyspnea scale 7/10 at completion
- **Echocardiogram:** Estimated RVSP 48 mmHg (elevated); mild RV dilation; normal LV function, EF 60%

### Clinical Image

![HRCT findings in asbestosis](case_01_image.jpg)

*High-resolution CT scan illustration showing characteristic bilateral lower lobe subpleural reticular opacities, honeycombing, and calcified pleural plaques in asbestosis. Source: Educational illustration.*

### Diagnosis
**Asbestosis with Secondary Pulmonary Hypertension**

**Key Diagnostic Criteria:**
- Reliable history of significant asbestos exposure (25 years, heavy occupational exposure with inadequate respiratory protection)
- Appropriate latency period (>15 years from first exposure to symptom onset)
- Radiographic evidence: bilateral lower-lobe predominant interstitial fibrosis with honeycombing on HRCT; calcified pleural plaques (hallmark of asbestos exposure)
- Restrictive physiology on PFT with severely reduced DLCO
- Exclusion of other causes of pulmonary fibrosis (negative autoimmune serologies, no drug-related causes)
- Clinical findings: bilateral basilar crackles and digital clubbing

### Treatment Plan
1. **Supportive care:** Supplemental oxygen therapy — 2-3 L/min via nasal cannula to maintain SpO2 ≥90% at rest and with exertion
2. **Pulmonary rehabilitation:** 8-12 week supervised program with aerobic conditioning and breathing retraining
3. **Antifibrotic therapy consideration:** Referral to ILD specialist for evaluation of nintedanib (FDA-approved for progressive fibrosing ILD; emerging evidence in asbestosis with progressive phenotype)
4. **Pulmonary hypertension management:** Right heart catheterization to confirm; consider pulmonary vasodilator therapy if confirmed pre-capillary PH
5. **Surveillance for malignancy:** Annual low-dose CT chest for lung cancer screening (combined asbestos exposure + smoking history confers multiplicative risk); serial mesothelin levels for mesothelioma surveillance
6. **Vaccinations:** Annual influenza; pneumococcal (PCV20); COVID-19 booster; RSV vaccination
7. **Workers' compensation:** Assist with filing occupational disease claim; comprehensive occupational exposure documentation
8. **Advance care planning:** Discussion of disease trajectory and goals of care given progressive nature

### Key Learning Points
- Asbestosis is a dose-dependent pneumoconiosis with a latency period of 15-40 years; it is characterized by bilateral lower-lobe predominant interstitial fibrosis indistinguishable from UIP pattern except by exposure history and presence of pleural plaques
- Calcified pleural plaques are the most specific radiographic marker of prior asbestos exposure but are distinct from asbestosis (parenchymal disease); plaques alone do not cause functional impairment
- The combination of asbestos exposure and cigarette smoking has a multiplicative (not merely additive) effect on lung cancer risk, increasing risk by approximately 50-90 fold compared to the unexposed non-smoker
- Asbestosis is a progressive disease with no cure; management is supportive, with emerging evidence for antifibrotic agents in progressive fibrosing phenotypes
- Occupational medicine physicians play a critical role in exposure documentation, workers' compensation advocacy, and malignancy surveillance in asbestos-exposed populations

---

## Case 2: Noise-Induced Hearing Loss

### Patient Presentation
**Demographics:** 45-year-old male manufacturing plant press operator

**Chief Complaint:** "My wife says I'm turning the TV up too loud, and I've been having trouble hearing conversations at work — especially when there's background noise."

**History of Present Illness:**
Mr. T.R. is referred to the occupational medicine clinic after his annual workplace audiometric screening revealed a significant bilateral high-frequency hearing loss, with a notable 15 dB threshold shift at 4000 Hz in the right ear compared to his baseline audiogram from 5 years ago. He has worked as a hydraulic press operator at an automotive stamping plant for 22 years. He reports that the noise level in his work area is consistently loud and that he can feel vibrations from the press through the floor.

He describes gradually progressive difficulty hearing conversations, particularly in noisy environments such as the plant floor, restaurants, and family gatherings. He frequently asks people to repeat themselves and has difficulty hearing his telephone unless the volume is at maximum. He also reports bilateral tinnitus — a constant high-pitched ringing that is worse in the right ear and more noticeable in quiet environments. The tinnitus has been present for approximately 5 years but has worsened over the past year.

He states he was provided foam earplugs from the beginning of employment but acknowledges inconsistent use during his first 10 years ("they were uncomfortable and I couldn't hear my coworkers"). He has been more compliant with hearing protection over the past 12 years, using both foam plugs and over-ear muffs. Despite this, noise exposure measurements at his workstation (performed by the company industrial hygienist 6 months ago) recorded 95-102 dBA TWA (time-weighted average), exceeding the OSHA Permissible Exposure Limit of 90 dBA.

**Past Medical History:**
- Type 2 diabetes mellitus (diagnosed 3 years ago, HbA1c 7.2%)
- Hyperlipidemia
- No history of ear infections, ear surgery, or head trauma
- No ototoxic medication use

**Medications:**
- Metformin 1000 mg BID
- Atorvastatin 20 mg daily

**Social History:**
- Non-smoker
- Recreational firearms use (deer hunting) for 20 years; inconsistent use of hearing protection while hunting
- Occasional power tool use at home (table saw, circular saw)
- No recreational headphone/earbud use with loud music
- Married, 2 children (ages 14 and 17)

**Family History:**
- Father: hearing aids at age 70 (attributed to aging)
- No family history of early-onset hearing loss

### Physical Examination
- **Vital Signs:** BP 134/82 mmHg, HR 76 bpm, RR 14, SpO2 98%, Temp 36.7°C, BMI 31.2 kg/m²
- **HEENT:** External ears normal bilaterally; otoscopic examination reveals intact tympanic membranes bilaterally with normal landmarks, no effusion, no cerumen impaction
- **Weber test:** Lateralizes to the left ear (better hearing ear)
- **Rinne test:** Air conduction > bone conduction bilaterally (positive Rinne bilaterally, consistent with sensorineural hearing loss)
- **Cranial nerves:** Otherwise intact; no nystagmus; vestibular function grossly normal
- **Neck:** No lymphadenopathy, no masses

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| HbA1c | 7.2% | <5.7% (normal) |
| Fasting glucose | 142 mg/dL | 70-100 mg/dL |
| Creatinine | 0.9 mg/dL | 0.7-1.3 mg/dL |
| TSH | 2.4 mIU/L | 0.4-4.0 mIU/L |

**Imaging/Additional Studies:**
- **Pure-tone audiometry:** Bilateral sensorineural hearing loss (SNHL); characteristic 4-kHz "noise notch" with recovery at 8 kHz bilaterally; Right ear: 15 dB at 500 Hz, 20 dB at 1000 Hz, 25 dB at 2000 Hz, 55 dB at 3000 Hz, 65 dB at 4000 Hz, 50 dB at 6000 Hz, 35 dB at 8000 Hz; Left ear: 10 dB at 500 Hz, 15 dB at 1000 Hz, 20 dB at 2000 Hz, 45 dB at 3000 Hz, 55 dB at 4000 Hz, 45 dB at 6000 Hz, 30 dB at 8000 Hz
- **Speech discrimination scores:** Right ear 72%, Left ear 80% (reduced bilaterally)
- **Tympanometry:** Type A (normal) bilaterally; acoustic reflexes present but elevated bilaterally
- **OSHA Standard Threshold Shift (STS) calculation:** >10 dB average shift at 2000, 3000, and 4000 Hz in right ear compared to baseline — confirmed STS
- **Workplace noise dosimetry (most recent):** 98 dBA TWA at operator station; peak impulse levels 115 dBC during press strikes

### Clinical Image

![Audiogram showing noise-induced hearing loss pattern](case_02_image.jpg)

*Audiogram illustrating the characteristic bilateral high-frequency sensorineural hearing loss with the classic 4-kHz "noise notch" and recovery at 8 kHz seen in noise-induced hearing loss. Source: Educational illustration.*

### Diagnosis
**Bilateral Noise-Induced Hearing Loss (NIHL), Moderate Severity, Occupational**

**Key Diagnostic Criteria:**
- Chronic occupational noise exposure exceeding OSHA PEL (98 dBA TWA vs. 90 dBA PEL)
- Bilateral sensorineural hearing loss with characteristic 4-kHz notch pattern
- OSHA Standard Threshold Shift confirmed (>10 dB average shift at 2000/3000/4000 Hz)
- Progressive decline documented on serial audiometric surveillance
- Consistent clinical history with gradual onset, bilateral involvement, and associated tinnitus
- No alternative etiology identified (no conductive component, no ototoxic medications, no acoustic neuroma suspected)
- Contributing factors: recreational noise exposure (firearms), diabetes mellitus (microvascular cochlear damage)

### Treatment Plan
1. **OSHA recordkeeping:** Record STS on OSHA 300 Log as work-related hearing loss; notify employee in writing within 21 days
2. **Enhanced hearing conservation:**
   - Fit-test for custom-molded earplugs with NRR ≥25 dB
   - Dual protection (plugs + muffs) mandatory given exposures >100 dBA
   - Engineering controls evaluation: press enclosure, vibration dampening, noise barriers
   - Administrative controls: rotation to reduce cumulative daily exposure
3. **Audiological rehabilitation:**
   - Referral to audiologist for hearing aid evaluation (bilateral)
   - Assistive listening devices for workplace communication
   - Aural rehabilitation program for communication strategies
4. **Tinnitus management:**
   - Sound therapy (white noise generators/maskers)
   - Cognitive behavioral therapy for tinnitus distress if significant
   - Avoid silence (use ambient sound machines at night)
5. **Medical optimization:**
   - Improve diabetes control (target HbA1c <7.0%) to reduce microvascular contribution
   - Avoid ototoxic medications (aminoglycosides, high-dose aspirin, loop diuretics)
6. **Recreational noise counseling:** Mandatory hearing protection for firearms use; electronic shooting ear muffs recommended
7. **Workers' compensation:** File claim for occupational hearing loss; schedule impairment rating per AMA Guides (binaural hearing impairment calculation)
8. **Follow-up audiometry:** Every 6 months (increased frequency due to confirmed STS)

### Key Learning Points
- Noise-induced hearing loss is the most common occupational disease in the United States and is entirely preventable; OSHA's Hearing Conservation Program (29 CFR 1910.95) mandates protection for workers exposed to ≥85 dBA TWA
- The characteristic audiometric pattern is a bilateral, roughly symmetric, sensorineural high-frequency loss with maximal deficit at 4000 Hz (the "4-kHz notch") and partial recovery at 8000 Hz, distinguishing it from presbycusis (age-related loss without notch)
- Standard Threshold Shift (STS) is defined as a ≥10 dB average change at 2000, 3000, and 4000 Hz in either ear compared to baseline; age correction is optional and controversial
- Diabetes mellitus is an independent risk factor for hearing loss via microvascular damage to the cochlear stria vascularis and is synergistic with noise exposure
- NIHL is irreversible because it results from permanent destruction of outer hair cells in the organ of Corti; the only treatment is hearing amplification and prevention of further damage

---

## Case 3: Work-Related Carpal Tunnel Syndrome

### Patient Presentation
**Demographics:** 38-year-old female poultry processing plant worker

**Chief Complaint:** "My hands go numb at night and I keep dropping things at work — it's been getting worse for about 8 months."

**History of Present Illness:**
Ms. A.C. presents to the occupational health clinic with progressive bilateral hand numbness, tingling, and weakness, worse on the right (dominant) side. She works on a poultry processing line where she performs repetitive cutting, deboning, and trimming motions with a knife for 8-10 hours per shift, 5-6 days per week. Her job requires sustained grip force, repetitive wrist flexion and extension, and exposure to cold temperatures (processing area maintained at 4°C / 40°F).

She reports nocturnal paresthesias in the thumb, index, and middle fingers bilaterally that wake her from sleep 3-4 times per night. She shakes her hands to relieve symptoms ("flick sign" positive). During the day, she experiences numbness while performing cutting motions at work, and has noticed progressive difficulty with fine motor tasks such as buttoning shirts and picking up small objects. She dropped a knife at work twice last month and is concerned about injury risk.

Symptoms began insidiously approximately 14 months ago but have accelerated over the past 8 months since her line speed was increased by 15% due to staffing shortages. She reports that several coworkers have similar complaints. She has tried wrist splints purchased at a pharmacy with partial nighttime relief.

**Past Medical History:**
- Gestational diabetes during second pregnancy (resolved postpartum)
- Hypothyroidism (diagnosed 2 years ago)
- Obesity (BMI 34)
- Two uncomplicated vaginal deliveries

**Medications:**
- Levothyroxine 75 mcg daily
- Ibuprofen 400 mg TID PRN (self-treating hand pain)

**Social History:**
- Non-smoker
- No alcohol use
- Immigrated from Guatemala 12 years ago; bilingual Spanish/English
- Single mother, 2 children (ages 6 and 9)
- No hobbies requiring repetitive hand use
- Works overtime frequently due to financial necessity

**Family History:**
- Mother: diabetes mellitus type 2, carpal tunnel syndrome (bilateral releases)
- Father: unknown medical history

### Physical Examination
- **Vital Signs:** BP 128/80 mmHg, HR 74 bpm, RR 14, SpO2 99%, Temp 36.6°C, BMI 34.1 kg/m²
- **Hands/Wrists:**
  - Thenar atrophy noted on right hand (moderate); left thenar eminence mildly flattened
  - Tinel sign: Positive bilaterally (right > left) — tingling in median nerve distribution with percussion at carpal tunnel
  - Phalen test: Positive bilaterally at 15 seconds (right) and 25 seconds (left)
  - Durkan compression test: Positive bilaterally
  - Decreased two-point discrimination: Right thumb 8 mm, right index finger 7 mm (normal <6 mm); left within normal limits
  - Grip strength (dynamometry): Right 18 kg, Left 24 kg (expected ~30 kg for age/sex)
  - Pinch strength (tip pinch): Right 3.5 kg, Left 5.2 kg (expected ~7 kg)
- **Upper extremity neurological:** Sensation diminished to light touch and pinprick in median nerve distribution (thumb, index, middle finger, radial half of ring finger) bilaterally, right > left; ulnar nerve distribution intact; radial nerve distribution intact; motor testing reveals 4/5 thumb opposition and abductor pollicis brevis on right, 5-/5 on left
- **Cervical spine:** Full ROM, no radiculopathy signs, negative Spurling test

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| TSH | 3.8 mIU/L | 0.4-4.0 mIU/L |
| Free T4 | 1.1 ng/dL | 0.8-1.8 ng/dL |
| Fasting glucose | 102 mg/dL | 70-100 mg/dL |
| HbA1c | 5.8% | <5.7% (normal) |
| CRP | 2.1 mg/L | <3.0 mg/L |
| Rheumatoid factor | Negative | <14 IU/mL |
| Vitamin B12 | 380 pg/mL | 200-900 pg/mL |

**Imaging/Additional Studies:**
- **Nerve conduction studies (NCS):** Right median motor distal latency 5.8 ms (normal <4.4 ms, severely prolonged); right median sensory latency 4.2 ms (normal <3.5 ms); left median motor distal latency 4.9 ms (moderately prolonged); left median sensory latency 3.8 ms (mildly prolonged); ulnar nerve studies normal bilaterally; no evidence of proximal median neuropathy or cervical radiculopathy
- **Electromyography (EMG):** Fibrillation potentials and positive sharp waves in right abductor pollicis brevis (denervation changes); chronic neurogenic motor unit changes in right opponens pollicis; left APB shows mild chronic changes without active denervation
- **Wrist ultrasound:** Right median nerve cross-sectional area at carpal tunnel inlet: 14 mm² (normal <10 mm²); left: 12 mm²; flexor tenosynovitis with increased Doppler signal bilaterally
- **Ergonomic job analysis:** Task involves >30,000 repetitive cutting motions per shift; sustained grip force >4 kg; wrist deviation >30° from neutral in flexion/extension and ulnar deviation; cold exposure at 4°C; vibration exposure from knife

### Clinical Image

![Carpal tunnel syndrome anatomy and nerve conduction findings](case_03_image.jpg)

*Anatomical illustration of the carpal tunnel showing median nerve compression beneath the transverse carpal ligament, with corresponding nerve conduction study waveforms demonstrating prolonged distal latency. Source: Educational illustration.*

### Diagnosis
**Bilateral Carpal Tunnel Syndrome — Right: Severe (with axonal loss); Left: Moderate — Occupational**

**Key Diagnostic Criteria:**
- Classic symptoms: nocturnal paresthesias in median nerve distribution, positive flick sign, progressive weakness
- Positive provocative tests: Tinel, Phalen, Durkan compression bilaterally
- Thenar atrophy on right indicating chronic denervation
- Electrodiagnostic confirmation: prolonged median motor and sensory distal latencies bilaterally; active denervation (fibrillations) in right APB
- Temporal association with occupational exposure: high-repetition, high-force, cold-temperature work
- Ergonomic analysis confirming multiple established CTS risk factors (repetition >30/min, force, non-neutral posture, cold, vibration)
- Contributing personal risk factors: obesity, pre-diabetes, hypothyroidism, prior gestational diabetes, female sex

### Treatment Plan
1. **Right hand (severe with denervation):**
   - Urgent referral for carpal tunnel release surgery (open or endoscopic)
   - Pre-operative optimization of glycemic status
   - Post-operative rehabilitation: 4-6 weeks modified duty, progressive return to activity
2. **Left hand (moderate without denervation):**
   - Neutral wrist splinting (cock-up splint) at night and during symptomatic activities
   - Trial of corticosteroid injection (methylprednisolone 40 mg + 1 mL lidocaine into carpal tunnel under ultrasound guidance)
   - If inadequate response at 6-8 weeks, surgical consultation
3. **Workplace modifications (mandatory):**
   - Ergonomic redesign: ergonomic knife handles, anti-vibration tool wraps, adjustable workstation height
   - Job rotation: limit continuous cutting to 2-hour intervals with 15-minute alternative task breaks
   - Anti-vibration gloves; insulated gloves for cold exposure mitigation
   - Reduction of line speed to previous rate; OSHA reporting of ergonomic hazard
4. **Medical management of contributing conditions:**
   - Weight management counseling and referral to dietitian
   - Monitor HbA1c; lifestyle modification for pre-diabetes prevention
   - Continue levothyroxine; recheck TSH in 6 weeks
   - Discontinue ibuprofen TID (GI risk); substitute topical diclofenac or acetaminophen
5. **Workers' compensation:** File claim for bilateral occupational CTS; schedule impairment rating after maximum medical improvement
6. **Return to work:** Modified duty immediately (no repetitive gripping/cutting with right hand); full duty after surgical recovery with ergonomic accommodations

### Key Learning Points
- Carpal tunnel syndrome is the most common entrapment neuropathy and among the most prevalent work-related musculoskeletal disorders; occupational risk factors include repetition (>30 motions/min), force (>4 kg grip), non-neutral wrist posture, vibration, and cold exposure
- Electrodiagnostic studies (NCS/EMG) remain the gold standard for confirming CTS and grading severity; the presence of fibrillation potentials indicates active denervation and is an indication for surgical decompression
- Personal risk factors (obesity, diabetes, hypothyroidism, pregnancy, female sex) interact synergistically with occupational exposures; a condition can be both personally predisposed and occupationally aggravated
- Thenar atrophy represents irreversible motor axon loss; surgical decompression should be performed before this stage for optimal outcomes, though even patients with atrophy may benefit from surgery
- OSHA does not have a specific ergonomics standard (the 2001 Ergonomics Rule was repealed), but the General Duty Clause (Section 5(a)(1)) can be used to cite employers for recognized ergonomic hazards causing serious injury