ESPE Abstracts

Background: Pediatric osteoporosis is a condition which can stem from genetic causes (Primary osteoporosis), from systemic diseases or from the chronic use of drugs that alter bone metabolism (secondary osteoporosis). Obesity affects bone health in several ways, including bone remodeling, proinflammatory cytokine production and bone marrow microenvironment alteration. We describe the case of a boy who presented spontaneous vertebral fractures.

Clinical History: F. is a full-term child born from unrelated parents. Nothing relevant was present in his clinical history until the age of 9 when F. started suffering from pain in the dorsal and lumbar region, in the absence of trauma. Physical examination was normal, except for severe obesity (BMI > 99°), and vitamin D deficiency for which he began oral supplementation (1000 IU/day). Given the aggravation of pain which made independent walking impossible, a magnetic resonance imaging (MRI) of the spine was performed. As a result, a wedging and bone edema of L1 was revealed. At the Dual-energy X-ray absorptiometry (DXA) assessment: Z-score -2.4. An orthopedic immobilization corset was recommended. MRI performed after three months showed new vertebral collapses, and DXA documented further reduction in BMD (Z score -3.2). F. was referred to the pediatric endocrinologist who performed blood test to exclude the most common causes of secondary osteoporosis and increased oral vitamin D supplementation to 2500 IU/day. Bone remodeling markers were found to be normal. Considering the severity of the clinical picture, it was decided to perform a genetic investigation of the genes related to bone fragility and to start intravenous infusion of neridronate at a dose of 1 mg/kg. The genetic analysis was done through a NGS-targeted panel including the main known genes affecting syndromic and non-syndromic bone fragility. A rare variant of the exon 10 of the LRP5 (NM_002335), c.2236C>T, p.(Arg746Trp) was found. This variant not reported in public population databases (PM2), occurs in a gene in which missense variants are common cause of disease (PP2) and is predicted ‘deleterious’ in silico (PP3). Two months after the infusion, F. showed marked clinical improvement and started walking again. F. will perform two more neridronate infusions quarterly, and lateral spine X-ray and DXA will then be reassessed. Although the genetic bases of constitutional forms of bone fragility remain incompletely understood, tailored molecular testing represents the ultimate resource for the assessment and decision making in complex cases.