What workup and treatment should be done for a 17-year-old with a body mass index (BMI) of 13.3, severe underweight status, and a family history of anemia and diabetes, despite being asymptomatic?

Comprehensive Workup for Severely Underweight Adolescent with Family History of Anemia and Diabetes

A 17-year-old with a BMI of 13.3 requires immediate comprehensive evaluation for severe malnutrition, anemia, and metabolic disorders, even in the absence of symptoms. The extremely low BMI indicates severe underweight status that demands urgent nutritional intervention alongside diagnostic workup for underlying conditions.

Initial Laboratory Assessment

• Complete blood count (CBC) with differential to assess for anemia and other hematologic abnormalities 1
• Iron studies including serum ferritin, transferrin saturation (TSAT) 1
• Vitamin B12 and folate levels to evaluate for nutritional deficiencies 1
• Fasting glucose and HbA1c to screen for diabetes given the family history 1
• Comprehensive metabolic panel including:
  • Liver function tests
  • Kidney function (eGFR)
  • Electrolytes
  • Total protein and albumin 1
• Lipid profile to assess for dyslipidemia 1, 2
• Thyroid function tests (TSH, free T4)

Additional Evaluations

• Nutritional assessment using the Edmonton Obesity Staging System for Pediatrics (EOSS-P) to evaluate metabolic, mechanical, mental health, and social milieu domains 1
• Screening for eating disorders using validated tools
• Bone density scan to assess for osteopenia/osteoporosis due to severe malnutrition

Nutritional Intervention

• Calculate energy requirements at approximately 30 kcal/kg actual body weight for severely underweight patients 1
• Implement cautious refeeding with slow increase in calories to avoid refeeding syndrome 1
• Protein intake should be 1.2-1.5 g/kg body weight/day if renal function is normal 1, 2
• Micronutrient supplementation including iron, folate, vitamin B12, and multivitamins

Management Algorithm

1. If anemia is detected:

   • Determine type (microcytic, macrocytic, normocytic)
   • Treat according to cause:
     • Iron deficiency: oral iron supplementation
     • B12/folate deficiency: appropriate vitamin supplementation
   • Note that HbA1c values may be affected by anemia and should be interpreted with caution 3

2. If abnormal glucose metabolism is detected:

   • For A1C <8.5% and asymptomatic: Consider metformin if renal function is normal 1
   • For marked hyperglycemia (blood glucose ≥250 mg/dL, A1C ≥8.5%): Consider basal insulin while initiating metformin 1

3. Nutritional rehabilitation plan:

   • Start with 75-80% of calculated energy needs and increase gradually
   • Monitor for signs of refeeding syndrome (electrolyte abnormalities, fluid shifts)
   • Weekly weight checks with goal of 0.5-1 kg weight gain per week

Follow-up Plan

• Weekly visits for the first month to monitor weight gain and vital signs
• Laboratory reassessment after 4 weeks of nutritional intervention
• Multidisciplinary team approach including physician, dietitian, and mental health professional

Important Considerations

• Risk of refeeding syndrome is high with BMI <14; monitor phosphate, magnesium, potassium, and glucose closely during initial refeeding 1
• Avoid rapid weight gain which can lead to metabolic complications
• Screen for mental health issues as they commonly co-occur with severe malnutrition
• Family-based approach is essential for sustainable improvement 1

This approach addresses both the immediate nutritional crisis and the diagnostic workup needed to identify potential underlying conditions contributing to the patient's severely underweight status.