SAT-213 - When Rickets Isn'T Simple: A Severe Multisystem Presentation in A 6-Month-Old Infant

Background: Severe rickets can present with multisystem involvement, electrolyte instability, and nutritional challenges. We describe a 6-month-old male with profound vitamin D deficiency and multisystem complications.
Clinical

Case: A 6-month-old male, born late preterm at 36 weeks, with a medical history of eczema, presented with progressive vomiting, fatigue, hypotonia, and developmental regression. Since being discharged home, he had lost nearly 2 pounds and was unable to hold his head up. He had been tolerating 24 cal per ounce of breast milk fortified by infant formula for proper weight gain. Initial labs at his clinic visit revealed severe hypocalcemia (6.1 mg/dl), hyponatremia (125 mEq/L), hypoalbuminemia (2.8 g/dl), hypoproteinemia, elevated both ALT and AST. He was referred to the emergency department (ED). In the ED, he appeared alert, with poor tone, midfacial hypoplasia, and edematous. Labs confirmed low calcium, sodium, magnesium, and albumin, along with leukocytosis and thrombocytosis. Abdominal ultrasound ruled out pyloric stenosis. He received a fluid bolus and was admitted to the PICU. Calcium remained critically low, requiring multiple IV calcium infusions. Endocrine evaluation showed 25-hydroxyvitamin D < 7 ng/mL, PTH 645 pg/mL, and low 1,25-dihydroxyvitamin D, consistent with vitamin D deficient rickets. Radiographs of the wrists and ankles supported this diagnosis. Treatment included oral calcitriol 0.05 mcg/kg/day, elemental calcium 80–100 mg/kg/day, vitamin D 3,000 IU daily, and specialized infant formulas (hydrolyzed then amino acid based) for feeding. Due to persistent diarrhea and hypoalbuminemia, he required continuous feeds and then switched to TPN. Evaluation for protein losing enteropathy was negative. He developed tachypnea, mild pulmonary edema, mild to moderate left ventricular dysfunction (EF44%), mitral regurgitation, elevated BNP, and anemia (Hgb 6.5g/dl), requiring blood transfusion. Electrolytes gradually stabilized with supplementation of calcium, vitamin D, phosphorus, magnesium, and potassium. He received two albumin infusions and furosemide. He became septic with positive blood cultures for Enterococcus faecalis and Staphylococcus aureus, treated with IV antibiotics. Respiratory status improved with supportive care. Whole-genome sequencing was pursued and was negative.

Conclusion: This case illustrates a severe multisystem presentation of nutritional rickets, in which profound vitamin D deficiency led to hypocalcemia, hypotonia, feeding intolerance, cardiac dysfunction, and failure to thrive. Early recognition and coordinated multidisciplinary management were essential for clinical stabilization.

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