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Paradoxical Low Bone Mineral Density in a 13-Year-Old Boy with multiple fractures and a CLCN7 Variant: A Mild Form of Osteopetrosis
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Jila Yousefi    |
| Kurdistan University of Medical Sciences , jila.yousefi@mail.com |
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Abstract: (125 Views) |
Background and Aim: Osteopetrosis is a rare hereditary skeletal disorder characterized by defective osteoclast-mediated bone resorption, resulting in abnormal bone modeling and remodeling. CLCN7 encodes the chloride/proton antiporter ClC-7, and variants in this gene underlie both autosomal recessive and dominant forms of osteopetrosis. Although increased bone mineral density (BMD) is typical, certain CLCN7 variants cause paradoxically low or normal BMD due to partial impairment of osteoclast acidification. Here, we report a 13-year-old boy with recurrent fractures and low BMD associated with a heterozygous CLCN7 variant, expanding the known clinical spectrum of the disorder.
Case Presentation: A 13-year-old boy presented with three low-trauma fractures over ten months, involving the distal radius, right elbow, and finger. Physical examination and growth parameters were normal. Laboratory results, including calcium, phosphate, alkaline phosphatase, parathyroid hormone, and vitamin D, were within normal limits. Dual-energy X-ray absorptiometry (DXA) showed low bone mineral density (T-scores: spine −2.0 to −3.52; left hip -3.05 to -3.13; total bone mineral density −2.77). Radiographs revealed mild metaphyseal splaying, alternating radiolucent metaphyseal band, and mild cortical thickening without generalized sclerosis. Moreover, genetic testing identified a heterozygous variant in CLCN7:c.1692G>A, both results consistent with a mild form of osteopetrosis.
Conclusion: This case demonstrates that CLCN7-related osteopetrosis may present with paradoxically low BMD due to structural disorganization and defective remodeling rather than increased mineralization. Diagnosis requires integration of clinical, radiologic, and genetic data, as reliance on BMD alone may lead to misclassification of disease as primary osteoporosis or osteogenesis imperfecta |
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| Keywords: : Osteopetrosis, Osteoclast, Bone Mineral Density, Heterozygous Variant, Dual-energy X-ray Absorptiometry, Bone Fractures |
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Type of Study: case report |
Subject:
Medicine - Pediatric
Received: 2025/11/26 | Accepted: 2026/04/19
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