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Full-Endoscopic Interlaminar Approach for Decompression of Lateral Recess Stenosis
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Phenotypic diversity in autosomal recessive hypophosphatemic rickets type 2
Maimoona Al Qanoobi1, Maryam Al Badi2, Aisha Al Sinani2
1Department of Pediatrics, Al Nahdha Hospital, P.O. Box 937, Near Wadi Adi Roundabout, Muscat 112, Sultanate of Oman.
Summary
Autosomal Recessive Hypophosphatemic Rickets Type 2 (ARHR2) presents with diverse symptoms due to ENPP1 gene mutations. Genetic testing is crucial for diagnosing this rare disorder and its related phosphate wasting.
Area of Science:
- Genetics
- Endocrinology
- Pediatrics
Background:
- Autosomal Recessive Hypophosphatemic Rickets Type 2 (ARHR2) is a rare genetic disorder.
- It is caused by biallelic mutations in the ENPP1 gene, leading to a wide range of clinical presentations.
- ENPP1 deficiency impacts phosphate metabolism and can cause rickets and other systemic issues.
Purpose of the Study:
- To describe the heterogeneous clinical features of ARHR2 in three siblings from a consanguineous family.
- To investigate the biochemical profile, including FGF23 and inorganic pyrophosphate (PPi) levels.
- To emphasize the diagnostic utility of genetic testing for ENPP1 mutations.
Main Methods:
- Clinical case description of three affected siblings and their father.
- Biochemical analyses including serum phosphate, alkaline phosphatase, TmP/GFR, FGF23, and plasma inorganic pyrophosphate (PPi).
- Genetic testing to identify ENPP1 gene variants.
Main Results:
- The siblings exhibited markedly heterogeneous clinical features, ranging from classical rickets to vascular stenoses and hearing loss.
- All affected children displayed hypophosphatemia, reduced TmP/GFR, and altered FGF23 levels, indicative of phosphate wasting.
- Markedly reduced plasma PPi levels were observed in affected individuals, with mild reduction in carriers.
- A homozygous ENPP1 variant (c.2559_2561del p.(Leu854del)) was identified in the affected siblings.
Conclusions:
- ENPP1 deficiency presents with significant clinical heterogeneity, underscoring the importance of recognizing diverse manifestations.
- Reduced plasma PPi levels are a key biochemical marker in ARHR2.
- Genetic testing for ENPP1 mutations is essential for accurate diagnosis and differentiation from other hypophosphatemic rickets.
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