X-linked hypophosphatemic rickets: importance in the differential diagnosis in pediatric patient with weight-height deficit of unknown cause
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Abstract
Introduction: X-linked hypophosphatemic rickets is a rare osteometabolic disease caused by mutations in the PHEX gene (Neutral Phosphate Regulatory Endopeptidase), located on
chromosome Xp22.11. Mutations in this gene lead to increased levels of fibroblast growth factor 23 (FGF-23), impairing phosphate absorption in renal tubular cells and intestinal epithelium. Case
reports: Case 1 Female patient, 11 years old, referred for investigation of weight and height deficit associated with bone deformity of the lower limb in varus; radiographic examinations were compatible with metaphyseal alterations suggestive of rickets. Case 2 Male patient, 8 years old, brother of case 1, referred to evaluate frequent falls and knee pain when walking, presented radiographic findings compatible with dolichocephaly, arching of the lower limbs in varus and metaphyseal dysplasia. Biochemical investigation of both was compatible with hypophosphatemic rickets, later genetically confirmed with identification of a pathogenic mutation in the PHEX
gene. Discussion: X-linked hypophosphatemic rickets is one of the main forms of genetically inherited rickets. Affected patients usually manifest symptoms even in childhood, such as delay in weightstatus growth, abnormal bone mineralization, dental alterations, craniosynostosis, in addition to osteomalacia and bone deformities in the lower limbs. Given the therapeutic advances in this area, it is essential that pediatricians recognize the early signs of this disease, so that not only is correct and accurate clinical management possible, but also that family genetic counseling is carried out.
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