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Phenotypic Variability in Vitamin D-Dependent Rickets Type 1a: A Case Report of Two Children With the Same CYP27B1
1Armed Forces Hospital Southern Region (AFHSR), Khamis Mushait, Saudi Arabia.
Case Reports in Pediatrics
|August 1, 2026
Summary
Vitamin D-dependent rickets Type 1A (VDDR1A) shows significant clinical variability despite identical genetic mutations. Early diagnosis and consistent active vitamin D therapy are crucial for preventing severe skeletal issues and optimizing growth in affected children.
Area of Science:
- Genetics
- Endocrinology
- Pediatrics
Background:
- Vitamin D-dependent rickets Type 1A (VDDR1A) is a rare genetic disorder caused by CYP27B1 gene mutations.
- It impairs the body's ability to produce active vitamin D, leading to calcium-phosphate imbalance and rickets.
- Clinical severity can vary significantly, even among individuals with the same mutation.
Purpose of the Study:
- To highlight the phenotypic variability of VDDR1A.
- To emphasize the importance of early diagnosis and consistent treatment.
- To underscore the impact of genetic mutations on rickets presentation.
Main Methods:
- Case report of two unrelated Saudi boys with genetically confirmed VDDR1A.
- Genetic analysis revealed a homozygous CYP27B1 c.1286G>C (p.Arg429Pro) variant in both patients.
- Clinical courses and treatment responses were compared.
Main Results:
- Both patients shared the same homozygous CYP27B1 mutation but presented with markedly different clinical outcomes.
- The first child experienced a favorable recovery with early treatment.
- The second child had severe skeletal deformities and complications due to delayed diagnosis and inconsistent treatment adherence.
Conclusions:
- Phenotypic variability in VDDR1A is substantial, even with identical CYP27B1 mutations.
- Early recognition and sustained active vitamin D therapy are critical for preventing severe skeletal complications.
- Optimizing growth and outcomes requires timely intervention, especially in populations with high consanguinity rates.
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