Diagnostic Workup for a 12-Year-Old Girl with Significant Underweight and Short Stature
For a 12-year-old girl at the 2nd percentile for weight (66 pounds) and 37th percentile for height (59 inches), a comprehensive laboratory evaluation should include complete blood count, comprehensive metabolic panel, thyroid function tests, celiac disease screening, IGF-1, IGFBP-3, and karyotype analysis to rule out Turner syndrome. 1
Initial Assessment of Growth Parameters
This patient presents with:
- Weight: 66 pounds (2nd percentile) - significantly underweight
- Height: 59 inches (37th percentile) - normal height
The discrepancy between weight and height percentiles suggests a nutritional issue rather than a primary growth disorder. However, a systematic evaluation is still necessary to rule out underlying pathology.
Laboratory Testing Algorithm
First-line Testing:
- Complete blood count (CBC) with differential
- Comprehensive metabolic panel (CMP) including:
- Electrolytes
- Liver function tests
- Kidney function tests
- Glucose
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
- Thyroid function tests (TSH, free T4)
- Tissue transglutaminase antibodies with total IgA (celiac disease screening)
- Urinalysis
Second-line Testing (based on initial findings):
- Growth hormone stimulation test if IGF-1 and IGFBP-3 are low
- Karyotype analysis to rule out Turner syndrome in girls with unexplained short stature 1
- Bone age assessment (left hand and wrist X-ray)
Rationale for Testing
Nutritional Assessment: The significant underweight status (2nd percentile) with normal height (37th percentile) suggests potential nutritional deficiency or malabsorption.
Rule Out Systemic Disease: CBC, CMP, ESR, and CRP will help identify chronic inflammatory conditions, malignancy, or organ dysfunction that could affect weight gain.
Endocrine Evaluation: Thyroid function tests are essential as hypothyroidism can present with growth issues and weight abnormalities.
Celiac Disease Screening: Celiac disease is a common cause of poor weight gain in children with normal height and should be ruled out.
Genetic Considerations: Although the height is normal, karyotype analysis should be considered if other tests are negative, as some genetic conditions like Turner syndrome can present with variable phenotypes 1.
Important Considerations
- While the patient's height is within normal range, the significant underweight status warrants thorough investigation
- Growth velocity should be calculated if previous measurements are available
- Family height patterns should be assessed to determine if the current height is appropriate for genetic potential
- Bone age assessment helps determine growth potential and can identify delayed or advanced skeletal maturation
Common Pitfalls to Avoid
- Focusing only on height without addressing the significant weight deficit
- Assuming constitutional delay without ruling out pathologic causes
- Failing to consider malabsorption disorders like celiac disease
- Overlooking the possibility of eating disorders in adolescent girls
- Delaying referral to pediatric endocrinology if initial workup is inconclusive
The diagnostic approach should be methodical but efficient to identify treatable causes of poor weight gain, as early intervention can significantly improve outcomes for morbidity, mortality, and quality of life 1, 2.