PC1194: A King's Secret: The Reason for Regression in a 14-month-old Male

Introduction: Developmental regression refers to the progressive loss of previously acquired skills across the five domains of development. The differential for regression is broad, and includes neurodegenerative genetic disorders, inborn errors of metabolism, structural brain disease, and infectious etiologies among many others. Regression is important to recognize and evaluate promptly as early identification and treatment of some causes may significantly alter the disease course.

Case Description: A 14-month-old vaccinated male with a recent viral exanthem presents with 8 weeks of progressive gross motor regression. He no longer walks, cruises, crawls, or sits unassisted as he previously had. There is no loss of social, cognitive, speech, or fine motor skills. No known fevers or trauma. Family history was non-contributory. The patient was born abroad and lived on a dairy farm in New Zealand until 5 months ago and has recent exposures to raw honey and a petting zoo. On exam, he is afebrile, with normal vital signs. Neurologic and musculoskeletal exams were pertinent for refusal to bear weight, sit upright, or crawl. He moves all extremities purposefully and spontaneously. He rolls over in both directions, although head lag is present, and he does not lift his head when prone. Exam was otherwise unremarkable. Laboratory evaluation, including metabolic and leukodystrophy screening, was unrevealing (Table 1). MRI spine was concerning for destruction of the L2-L3 disc with a fluid collection in the disc space, consistent with a diagnosis of L2-L3 spondylodiscitis (Figure 1; A,B). Interventional radiology performed disc space aspiration and bone biopsy for culture. Empiric IV cefazolin was initiated. Biopsy culture returned positive for Kingella kingae. At the end of 6 weeks of IV cefazolin therapy, repeat imaging demonstrated near complete resolution of destructive changes (Figure 1; C,D). With ongoing physical therapy he is now crawling, cruising, and sitting with improved endurance.

Discussion: Spondylodiscitis encompasses both infectious discitis and vertebral osteomyelitis. In children, it commonly presents as back pain, limp, irritability, and refusal to bear weight. These features were recognized as gross motor regression in our patient who had just learned to walk. The diagnosis requires a high index of suspicion and is often delayed in pediatrics because of the rarity (2-4 cases per 1,000,000 per year), but also complicated because of the poorly defined manifestations, in children who are often not able to clearly vocalize symptoms, as in our patient. Outcomes are often favorable although common sequelae of delayed diagnosis include residual kyphosis, back pain, and restricted spinal movement.

Conclusion: This case illustrates a complex presentation of a rare, treatable etiology of gross motor regression. It is important to recognize the signs and symptoms of pediatric spondylodiscitis to make a timely diagnosis and prevent further disease progression and morbidity.