A 52-year-old man with a 15-year history of occupational exposure to beryllium dust presents with progressive dyspnea, cough, and fatigue over 8 months. Chest X-ray shows diffuse interstitial infiltrates and hilar lymphadenopathy. Beryllium lymphocyte proliferation test (BeLPT) is positive. Transbronchial biopsy reveals non-caseating granulomas. Serum calcium is normal. What is the most likely diagnosis?

## Diagnosis: Chronic Beryllium Disease (CBD) ### Clinical Presentation **Key Point:** Chronic beryllium disease is a granulomatous lung disease caused by inhalation of beryllium dust in occupationally exposed individuals. It mimics sarcoidosis histologically but has a distinct occupational and immunological basis. This patient presents with: 1. **Occupational exposure history** — 15 years of beryllium dust exposure (aerospace, electronics, nuclear industries) 2. **Progressive pulmonary symptoms** — dyspnea, cough, fatigue 3. **Radiological findings** — diffuse interstitial infiltrates and hilar lymphadenopathy 4. **Histology** — non-caseating granulomas (indistinguishable from sarcoidosis) 5. **Positive BeLPT** — diagnostic immunological marker ### Pathophysiology **High-Yield:** Beryllium is a **hapten** that binds to lung proteins and triggers a **cell-mediated immune response** in genetically susceptible individuals (HLA-DP allele carriers). This leads to beryllium sensitization and, with continued exposure, chronic beryllium disease. ### Diagnostic Criteria for CBD | Criterion | Finding | |-----------|----------| | **Occupational exposure** | History of beryllium dust inhalation | | **Beryllium sensitization** | Positive BeLPT (lymphocyte proliferation test) | | **Clinical symptoms** | Progressive dyspnea, constitutional symptoms | | **Histology** | Non-caseating granulomas | | **Imaging** | Interstitial infiltrates, hilar lymphadenopathy | | **Exclusion** | Normal serum calcium (rules out sarcoidosis) | **Mnemonic:** **BeLPT** = **Be**ryllium **L**ymphocyte **P**roliferation **T**est — the gold standard for beryllium sensitization. ### Why CBD and Not Sarcoidosis? ```mermaid flowchart TD A[Non-caseating granulomas<br/>+ Hilar LAD]:::outcome --> B{Occupational exposure<br/>to beryllium?}:::decision B -->|Yes| C{BeLPT positive?}:::decision B -->|No| D{Hypercalcemia?}:::decision C -->|Yes| E[Chronic Beryllium Disease]:::action C -->|No| F[Beryllium sensitization<br/>without CBD]:::outcome D -->|Yes| G[Sarcoidosis]:::action D -->|No| H[Other granulomatous disease]:::outcome ``` **Clinical Pearl:** The **normal serum calcium** in this patient is crucial — it argues against sarcoidosis, where hypercalcemia is common due to granuloma-derived calcitriol production. CBD does not typically cause hypercalcemia. ### Beryllium Sensitization vs. Chronic Beryllium Disease | Feature | Beryllium Sensitization | Chronic Beryllium Disease | |---------|------------------------|--------------------------| | BeLPT | Positive | Positive | | Symptoms | Absent or mild | Progressive pulmonary disease | | Histology | No granulomas | Non-caseating granulomas | | Prognosis | May not progress | Progressive fibrosis | **Key Point:** This patient has **CBD** (not just sensitization) because he has symptomatic progressive disease with granulomatous inflammation on biopsy.