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Pediatr Nephrol. 2018 Jul;33(7):1263-1267. doi: 10.1007/s00467-018-3945-z. Epub 2018 Mar 28.

Hyperphosphatemic tumoral calcinosis caused by FGF23 compound heterozygous mutations: what are the therapeutic options for a better control of phosphatemia?

Author information

1
Centre de Référence des Maladies Rénales Rares, Centre de Référence des Maladies Rares du Calcium et du Phosphate, Hospices Civils de Lyon, Hôpital Femme Mère Enfant, 59 boulevard Pinel, 69677, Bron cedex, France.
2
INSERM, UMR 1033, Faculté de Médecine Lyon Est, site Laennec, Lyon, France.
3
Département de Biologie, Centre Hospitalier Lyon Sud, Pierre-Bénite, France.
4
Département d'Anatomopathologie, Groupe Hospitalier Est, Hospices Civils de Lyon, Bron, France.
5
Université de Lyon, 69008, Lyon, France.
6
Service de Chirurgie Orthopédique Pédiatrique, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Bron, France.
7
Service de Génétique et Biologie Moléculaires, Centre de Référence des Maladies Rares du Métabolisme du Calcium et du Phosphate, Filière OSCAR, Hôpital Cochin, Paris, France.
8
INSERM U1169, Hôpital Bicêtre, Le Kremlin-Bicêtre, France.
9
Centre de Référence des Maladies Rénales Rares, Centre de Référence des Maladies Rares du Calcium et du Phosphate, Hospices Civils de Lyon, Hôpital Femme Mère Enfant, 59 boulevard Pinel, 69677, Bron cedex, France. justine.bacchetta@chu-lyon.fr.
10
INSERM, UMR 1033, Faculté de Médecine Lyon Est, site Laennec, Lyon, France. justine.bacchetta@chu-lyon.fr.
11
Université de Lyon, 69008, Lyon, France. justine.bacchetta@chu-lyon.fr.

Abstract

BACKGROUND:

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disease caused by mutations in genes encoding FGF23 or its regulators, and leading to functional deficiency or resistance to fibroblast growth factor 23 (FGF23). Subsequent biochemical features include hyperphosphatemia due to increased renal phosphate reabsorption, and increased or inappropriately normal 1,25-dihydroxyvitamin D (1,25-D) levels.

CASE-DIAGNOSIS/TREATMENT:

A 15-year-old girl was referred for a 1.2-kg-calcified mass of the thigh, with hyperphosphatemia (2.8 mmol/L); vascular impairment and soft tissue calcifications were already present. DNA sequencing identified compound heterozygous mutations in the FGF23 gene. Management with phosphate dietary restriction, phosphate binders (sevelamer, aluminum, nicotinamide), and acetazolamide moderately decreased serum phosphate levels; oral ketoconazole was secondary administered, leading to significantly decreased 1,25-D levels albeit only moderate additionally decreased phosphate levels. However, therapeutic compliance was questionable. Serum phosphate levels always remained far above the upper normal limit for age. The patient presented with two relapses of the thigh mass, requiring further surgery.

CONCLUSIONS:

We suggest that control of phosphate metabolism is crucial to prevent recurrences and vascular complications in HFTC; however, the medical management remains challenging.

KEYWORDS:

Ectopic calcifications; Fibroblast growth factor 23; Hyperphosphatemic tumoral calcinosis; Ketoconazole; Phosphate

PMID:
29594503
DOI:
10.1007/s00467-018-3945-z

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