[Autosomal recessive hypophosphatemic rickets/osteomalacia caused by a novel mutation in the DMP1 gene: a case report and literature review].

Hereditary hypophosphatemic rickets/osteomalacia encompasses a group of disorders characterized by impaired bone mineralization resulting from phosphate deficiency, which can lead to skeletal deformities and growth retardation when onset occurs in early childhood. A patient with autosomal recessive hypophosphatemic rickets type 1 (ARHR1) caused by a mutation in the dentin matrix protein 1 (DMP1) gene was admitted to the Department of Endocrinology at the First Medical Center of Chinese PLA General Hospital in December 2024. The patient presented with frontal bossing, short stature, lower limb deformities, and generalized bone pain. Laboratory evaluation revealed hypophosphatemia, hyperphosphaturia, a decreased phosphate clearance index, elevated serum alkaline phosphatase, increased fibroblast growth factor 23, slightly reduced 25-hydroxyvitamin D, and normal serum calcium and parathyroid hormone levels. Genetic testing confirmed the presence of a homozygous mutation in the DMP1 gene. Literature retrieval indicated that more than 10 distinct mutations in this gene have been reported in approximately 30 patients worldwide. Most of these documented mutations are located within exon 6, likely because this region harbors up to 80% of the total coding sequence. However, whole-exome sequencing identified a novel homozygous variant c.457C>T (p.Gln153*) in exon 3 in this patient, as confirmed by database and literature review. ARHR1 remains an extremely rare disease, and hereditary genetic testing plays a vital role in establishing a definitive diagnosis.