Orthopaedist Beware: Severe Nutritional Rickets and Autism Spectrum Disorder.

Background: The prevalence of autism spectrum disorder (ASD) continues to rise in the United States, and many affected children have highly selective diets and sensory-driven food aversions that increase the risk of micronutrient deficiencies. In low-resource settings, food insecurity and limited access to autism evaluation and supportive services may further heighten this risk. At our urban tertiary pediatric center, we have diagnosed severe nutritional rickets in a number of children and adolescents with ASD and restrictive diets. This case series describes the clinical, metabolic, and orthopaedic manifestations of nutritional rickets in this population. Methods: We performed a retrospective chart review at a single urban tertiary children's hospital to identify pediatric and adolescent patients with ASD who presented with symptomatic nutritional rickets from 2019 to 2024. Patients were included if they had clinical findings concerning for rickets, laboratory evidence of vitamin D deficiency (with or without hypocalcemia), and radiographic findings consistent with rickets. We collected demographics, presenting symptoms, dietary patterns, key examination findings, laboratory values, imaging features, management, and outcomes, including follow-up calcium and vitamin D levels. Socioeconomic status was characterized using the Child Opportunity Index (COI) 2.0 by a residential ZIP code. Results: Eleven patients (age: 4-16 years) met the inclusion criteria. All patients resided in neighborhoods in the lowest COI quintile. All had 25-hydroxy vitamin D levels <10 ng/mL; 8 had serum calcium <7.0 mg/dL, and 3 presented with hypocalcemic seizures. Seven patients presented to the pediatric orthopaedic surgeon with a variety of musculoskeletal complaints, and radiographs commonly demonstrated genu valgum and rickets. Most patients improved with nutritional supplementation alone. At follow-up, serum calcium normalized in all patients, vitamin D normalized in 4 patients, remained low in 6, and was undetectable in 1 patient. Severe complications included bilateral femoral neck fractures requiring open reduction and internal fixation and deformity severe enough to require operative intervention (osteotomy and guided growth). Conclusions: Older children and adolescents with ASD and highly selective diets, particularly those living in very low-opportunity neighborhoods, may develop severe nutritional rickets with presentations ranging from subtle gait changes and progressive valgus deformity to hypocalcemic seizures. Orthopaedists should maintain a high index of suspicion for metabolic bone disease in this population and obtain a focused dietary history, targeted laboratory testing, and radiographs to enable timely treatment and prevent morbidity. Key Concepts: (1)Older children and adolescents with autism spectrum disorder (ASD) and highly selective diets, particularly those living in very low-opportunity neighborhoods, can develop severe nutritional rickets and may present first to the orthopaedic surgeon.(2)Presentations range from subtle gait changes and/or progressive genu valgum to hypocalcemic seizures.(3)Dietary history, targeted laboratory testing, and radiographs are essential for timely diagnosis and prevention of morbidity. Level of Evidence: IV.