O2088: Orthopaedists Beware: Severe Nutritional Rickets and Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) has an increasing prevalence in the U.S. Some children with ASD have atypical eating habits, including food and texture aversions that can result in nutritional deficiencies. Low-income and food-insecurity can also increase the risk of nutrient deficiencies. Our urban, tertiary children’s hospital serves an area where the poverty rate is more than double the overall U.S. rate. In recent years, we have diagnosed severe nutritional rickets in multiple children with ASD who have restrictive eating habits. The purpose of this case series is to bring attention to the risk of nutritional rickets in this population, many who were found to have associated hypocalcemia requiring hospital admission.

Methods: The case series was compiled based on retrospective chart review. Pediatric and adolescent patients with ASD presenting with symptomatic nutritional rickets or osteomalacia were identified. The Child Opportunity Index (COI) 2.0, a national measure which reflects neighborhood conditions affecting a child’s healthy development, was recorded for each patient.

Results: Since 2021, nine patients presented with clinical and laboratory findings consistent with severe nutritional rickets in the setting of ASD and restrictive diets. All parents noted that their child had chronic, restrictive eating habits. All patients resided in zip-codes classified in the lowest COI quintile nationally. Initial laboratory tests for all patients were consistent with severe vitamin D deficiency and all but two had severe hypocalcemia requiring hospital admission for calcium infusions to prevent seizures and cardiac arrythmias. Two patients presented with new onset seizure-like activity secondary to hypocalcemia. Six patients presented with orthopaedic conditions: one sustained bilateral femoral neck fractures during a hypocalcemic seizure and another was noted to have severe but asymptomatic hypocalcemia on post-operative laboratory tests following distal femur osteotomies for bilateral genu valgum. Three patients presented with vague gait disturbances, increasing genu valgum and decreasing activity levels, one presented for toe-walking and decreasing activity level, and one was noted to be hypocalcemic on routine labs.

Conclusion: Vitamin D deficiency rickets classically is diagnosed in babies and toddlers who are predominantly breastfed and present with lower extremity bowing when they begin to walk. We present an atypical and previously undescribed population of patients with nutritional rickets: children and adolescents with ASD and restrictive diets from very low resource areas who often presented to the orthopaedic clinic with vague musculoskeletal symptoms. Patients were subsequently noted to have rickets on x-ray and then found to have both undetectable vitamin D levels and associated severe calcium deficiencies on lab testing. This highlights the importance of a high index of suspicion for metabolic bone disease and a low threshold for radiographic and laboratory testing among orthopaedists treating children with ASD, particularly in low resource areas.