目的　分析维生素D 依赖性佝偻病IA 型(VDDR-IA) 的临床特征，及1α- 羟化酶编码基因(CYP27B1) 突变。方法　回顾性分析2 例VDDR-IA 患儿的临床表现、实验室和影像学资料。对CYP27B1 基因9 个外显子及部分内含子相邻区域进行PCR 扩增和DNA 测序分析。结果　两例女性患儿，分别为1 岁10 个月及2 岁9 个月，有典型的佝偻病体征、实验室及影像学表现。基因测序发现CYP27B1 基因8 号外显子上均存在纯合突变c.1319_1325dupCCCACCC。家系中多人为单一杂合突变。两例患儿均予口服骨化三醇及钙剂治疗，病情稳定，随访中。结论　对于VDDR-IA 病例应注意c.1319_1325dupCCCACCC 纯合突变。

　Objective　To analyze the clinical characteristics and CYP27B1 gene mutation vitamin D-dependent rickets type IA (VDDR-IA) in two Chinese families. Methods　Clinical manifestations, laboratory data, and radiological findings were analyzed in two patients with VDDR-IA. Nine exons and intron-exon boundaries of CYP27B1 gene were amplified by PCR and sequenced. Results　Two female patients (22 and 33 months of age, respectively) had typical manifestations, laboratory, and radiological findings of rickets. Genetic sequencing identified a homozygous mutation in exon 8 of CYP27B1 gene (1319_1325dupCCCACCC). There were more than one person with single heterozygous mutation in two families. Two patients were treated with oral calcitriol and calcium. The condition were stable and continued follow up. Conclusions　It is important to detection c.1319_1325dupCCCACCC homozygous mutation in VDDR-IA patient.