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J Clin Res Pediatr Endocrinol. 2018 Jul 17. doi: 10.4274/jcrpe.0134. [Epub ahead of print]

Hyperphosphatemic Familial Tumoral Calcinosis in Two Siblings with a Novel Mutation in GALNT3 gene: Experience from Southern Turkey.

Author information

1
Çukurova University Faculty of Medicine, Department of Pediatric Rheumatology, Adana, Turkey.
2
Çukurova University Faculty of Medicine, Department of Pediatric Endocrinology, Adana, Turkey.
3
Çukurova University Faculty of Medicine, Department of Medical Genetics, Adana, Turkey.

Abstract

Inactivating autosomal recessive mutations in both FGF23, KL and GALNT3 genes lead to a rare disorder, hyperphosphatemic familial tumoral calcinosis (HFTC). Patients with HFTC constantly present hyperphosphatemia and tumor like soft tissue calcifications. Although 78% of patients develop their first symptoms between 2-13 years of age, diagnosis is usually delayed until adulthood. Some individuals with the same genetic defect overlap a condition named Hyperphosphatemic hyperostosis syndrome (HHS). Herein we report two siblings suffering from periarticular warm, hard and tender subcutaneous masses. Subcutaneous calcifications were present on X-ray and biopsy results were consistent with calcinosis in both patients. Laboratory results showed marked hyperphosphatemia and elevated renal tubular phosphate reabsorption, normal renal function tests and serum 25 hydroxyvitamin D levels. Thus, we suspected HFTC and performed next generation sequencing for GALNT3 gene, mostly causative in the literature. A novel homozygote P85Rfs*6 (c.254_255delCT) mutation in GALNT3 gene was identified in both siblings. Our report introduces two new patients to the knowledge about a rare genetic disease and suggests that small deletions in GALNT3 gene may be related with HFTC phenotype. Increased knowledge of physicians about this disease and studying phenotypegenotype correlation with more patients are needed to confirm our suggestion.

PMID:
30015621
DOI:
10.4274/jcrpe.0134
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