What is the appropriate diagnostic workup for an 18-year-old male (YOM) with unexplained weight loss, night sweats, and decreased appetite, who vapes daily and uses cannabis daily?

Diagnostic Workup for an 18-Year-Old Male with Unexplained Weight Loss, Night Sweats, and Decreased Appetite

The most appropriate initial diagnostic workup for this patient should focus on ruling out lymphoma, particularly Hodgkin's lymphoma, given his constellation of symptoms including unexplained weight loss, night sweats, and early satiety.

Initial Clinical Assessment

Key Symptoms Requiring Investigation

• Unexplained weight loss
• Night sweats
• Decreased appetite with early satiety
• No GERD history
• No nausea, vomiting, or diarrhea
• Daily vaping and cannabis use

High-Priority Diagnostic Tests

1. Complete Blood Count with Differential

   • To assess for cytopenias, leukocytosis, or abnormal cell morphology
   • Evaluate for leukoerythroblastic picture (suggests bone marrow involvement)

2. Comprehensive Metabolic Panel

   • Liver function tests (AST, ALT, alkaline phosphatase, bilirubin)
   • Kidney function (BUN, creatinine)
   • Serum albumin (malnutrition/chronic disease)
   • Electrolytes

3. Inflammatory Markers

   • Erythrocyte sedimentation rate (ESR)
   • C-reactive protein (CRP)

4. Chest X-ray

   • To evaluate for mediastinal lymphadenopathy or pulmonary involvement

5. Contrast-Enhanced CT Scan of Neck, Chest, and Abdomen

   • Essential for evaluating lymphadenopathy and organomegaly
   • Particularly important to assess for mediastinal masses 1

6. PET/CT Scan

   • If available, this should be performed for more accurate staging and assessment
   • High sensitivity for detecting bone marrow involvement 1

7. Excisional Lymph Node Biopsy

   • If lymphadenopathy is detected, an excisional biopsy (not fine needle aspiration) should be performed
   • Provides sufficient material for histopathological diagnosis 1

Specific Considerations for Cannabis Use

• Evaluate for Cannabinoid Hyperemesis Syndrome (CHS)

  • Though the patient denies vomiting, his early satiety and decreased appetite may be related to cannabis use 2
  • Consider this diagnosis particularly given his daily cannabis use

• Screen for withdrawal symptoms if hospitalization is required

  • May occur with consumption of >1.5g/day inhaled cannabis 1
  • Could potentially complicate inpatient management

Additional Testing Based on Initial Results

• Bone Marrow Biopsy

  • Only if PET/CT is not available or if specific hematologic abnormalities are detected 1

• HIV Testing

  • Important to rule out HIV infection, which can present with similar symptoms 1
  • HIV-associated lymphoma should be considered

• Tuberculosis Testing

  • Consider QuantiFERON-TB Gold or tuberculin skin test

Diagnostic Algorithm

1. First-line investigations: CBC, CMP, ESR, CRP, chest X-ray
2. Second-line investigations: CT scan of neck, chest, and abdomen
3. Third-line investigations: PET/CT (if available)
4. Fourth-line investigations: Targeted biopsies of abnormal findings

Important Diagnostic Considerations

• The combination of unexplained weight loss and night sweats in a young adult strongly suggests Hodgkin's lymphoma, which has a peak incidence in young adults aged 20-40 years 1

• While cannabis use could explain some symptoms, organic pathology must be ruled out first, as diagnostic yield of whole-body CT for unexplained weight loss is approximately 33.5% 3

• If initial workup is negative, consider a watchful waiting approach with close follow-up rather than pursuing increasingly invasive tests 4

• Gastrointestinal causes account for approximately 30% of unexplained weight loss cases, so endoscopic evaluation may be warranted if initial tests are inconclusive 5

Caution

• Do not attribute symptoms solely to cannabis use without completing a thorough evaluation for organic causes
• Early satiety with unexplained weight loss warrants investigation for malignancy, particularly lymphoma
• Avoid the common pitfall of assuming weight loss in a young person is benign or related to substance use without proper investigation