Atypical Hypotonia-Dominant Infantile Presentation of Genetically Confirmed Schwartz-Jampel Syndrome: A Case Report

Background Schwartz–Jampel syndrome (SJS) is an ultra-rare autosomal recessive disorder caused by mutations in the HSPG2 gene, which encodes the extracellular matrix protein perlecan. The condition is classically characterized by the triad of myotonia, skeletal dysplasia, and distinctive facial dysmorphism. Most patients with SJS type 1 develop symptoms during early childhood, primarily presenting with progressive muscle stiffness and skeletal abnormalities. However, atypical infantile presentations may occur, which can delay diagnosis. This case report describes an unusual hypotonia-dominant presentation of genetically confirmed SJS type 1 in a toddler and highlights the role of early physiotherapy intervention in improving functional motor outcome. Case presentation A 2-year-6-month-old girl born to non-consanguineous parents presented with global developmental delay and dysmorphic features. The child was delivered at term via lower segment cesarean section due to absent fetal movements. Neonatal history included jaundice, feeding difficulty, laryngeal stridor and patent ductus arteriosus. At four months, evaluation for absent neck control revealed facial dysmorphism including blepharophimosis and bilateral ptosis, narrow auditory canals and a sacral pit. Echocardiography later revealed atrial septal defect. Genetic testing identified a homozygous mutation in exon 1 of HSPG2 gene, confirming Schwartz- Jampel syndrome type 1. Unlike the typical presentation dominated by myotonia, the child demonstrated predominant hypotonia during infancy. Intervention Physiotherapy based on Neurodevelopmental Treatment (NDT) principles was initiated at 10 months of age. The rehabilitation program included prone extension exercises using a therapy ball, bridging with support, dynamic sitting balance training on a Swiss ball, balance board sitting, lower-limb weight-bearing activities, supported standing with reach tasks, whole-body vibration therapy, and tilt-table standing with ankle-foot orthoses. Outcomes Gradual improvement in motor milestones was observed. The child achieved neck control at 11 months, rolling at 15 months, supported sitting by 18 months followed by independent sitting, and supported standing at 27 months. Despite persistent hypotonia and poor truncal control, the child demonstrated voluntary grasping and functional interaction with objects. Conclusion This case highlights an atypical infantile presentation of SJS type 1 characterized predominantly by hypotonia rather than myotonia. Early genetic diagnosis and timely physiotherapy intervention may facilitate improved motor development and functional outcomes in children with this rare disorder.