Dental findings of hyperphosphatemic familial tumoral calcinosis

Successful treatment approaches for tumoral calcinosis in children and young people: A condition of diverse pathogenesis

BACKGROUND

Ectopic calcification is inappropriate biomineralization of soft tissues occurring due to genetic or acquired causes of hyperphosphataemia and rarely in normophosphataemic individuals. Tumoral Calcinosis (TC) is a rare metabolic bone disorder commonly presenting in childhood and adolescence with periarticular extra-capsular calcinosis. Three subtypes of TC have been recognised: primary hyperphosphataemic familial TC (HFTC), primary normophosphataemic familial TC and secondary TC most commonly seen in chronic renal failure. In the absence of established treatment, management is challenging due to variable success rates with medical therapies and recurrence following surgery.

AIM

We outline the successful treatment approaches in four children with TC (2 normophosphatemic TC, 2 HFTC) aged 2.5-10 years at initial presentation.

CASES

Patient 1 (P1) presented at 10 years with a painless lump behind the right knee, P2 with swelling of the right knee anteriorly at 9 years, P3 and P4 with pain and swelling over the right elbow at 5 and 2.5 years respectively. All patients were of Black African-Caribbean origin and were previously reported to be fit and well with no family history of TC.

RESULTS

P1, P2 had normophosphataemic TC and P3, P4 had HFTC with genetically confirmed GALNT3 mutation. All four patients had initial surgical resection with TC confirmed on histology. P1 had complete surgical resection with no recurrence at 27 months post-operatively. P2 had significant overgrowth of the tumour following surgery and was subsequently successfully managed with 25 % topical sodium metabisulphite (total duration of 8 months with a 4 month gap during which there was recurrence). P3 had post-surgical recurrence of TC on the right elbow and a new lesion on left elbow which resolved with oral acetazolamide monotherapy (15-20 mg/kg/day). P4 had recurrence of right elbow lesion following surgery and developed an extensive new hip lesion on sevelamer therapy which resolved completely with additional acetazolamide therapy (18-33 mg/kg/day). Acetazolamide was well tolerated with normal growth for 5 years in P3 and 6.5 years in P4 and no recurrence of lesions.

CONCLUSION

The frequent post-surgical recurrence in TC and successful medical therapy on the other hand indicates that medical management as first line therapy should be adopted. Monotherapies with topical 25 % sodium metabisulphite in normophosphataemic and oral acetazolamide in HFTC are effective treatment strategies which are well tolerated.

A Cross-Sectional Cohort Study of the Effects of FGF23 Deficiency and Hyperphosphatemia on Dental Structures in Hyperphosphatemic Familial Tumoral Calcinosis

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder caused by mutations in FGF23, GALNT3, KLOTHO, or FGF23 autoantibodies. Prominent features include high blood phosphate and calcific masses, usually adjacent to large joints. Dental defects have been reported, but not systematically described. Seventeen patients with HFTC followed at the National Institutes of Health underwent detailed clinical, biochemical, molecular, and dental analyses. Studies of teeth included intraoral photos and radiographs, high-resolution μCT, histology, and scanning electron microscopy (SEM). A scoring system was developed to assess the severity of tooth phenotype. Pulp calcification was found in 13 of 14 evaluable patients. Short roots and midroot bulges with apical thinning were present in 12 of 13 patients. Premolars were most severely affected. μCT analyses of five HFTC teeth revealed that pulp density increased sevenfold, whereas the pulp volume decreased sevenfold in permanent HFTC teeth compared with age- and tooth-matched control teeth. Histology revealed loss of the polarized odontoblast cell layer and an obliterated pulp cavity that was filled with calcified material. The SEM showed altered pulp and cementum structures, without differences in enamel or dentin structures, when compared with control teeth. This study defines the spectrum and confirms the high penetrance of dental features in HFTC. The phenotypes appear to be independent of genetic/molecular etiology, suggesting hyperphosphatemia or FGF23 deficiency may be the pathomechanistic driver, with prominent effects on root and pulp structures, consistent with a role of phosphate and/or FGF23 in tooth development. Given the early appearance and high penetrance, cognizance of HFTC-related features may allow for earlier diagnosis and treatment. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Hyperphosphatemic Tumoral Calcinosis: Pathogenesis, Clinical Presentation, and Challenges in Management

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare and disabling disorder of fibroblast growth factor 23 (FGF23) deficiency or resistance. The disorder is manifest by hyperphosphatemia, inappropriately increased tubular reabsorption of phosphate and 1,25-dihydroxy-Vitamin D, and ectopic calcifications. HFTC has been associated with autosomal recessive pathogenic variants in: (1) the gene encoding FGF23; (2) GALNT3, which encodes a protein responsible for FGF23 glycosylation; and (3) KL, the gene encoding KLOTHO, a critical co-receptor for FGF23 signaling. An acquired autoimmune form of hyperphosphatemic tumoral calcinosis has also been reported. Periarticular tumoral calcinosis is the primary cause of disability in HFTC, leading to pain, reduced range-of-motion, and impaired physical function. Inflammatory disease is also prominent, including diaphysitis with cortical hyperostosis. Multiple treatment strategies have attempted to manage blood phosphate, reduce pain and inflammation, and address calcifications and their complications. Unfortunately, efficacy data are limited to case reports and small cohorts, and no clearly effective therapies have been identified. The purpose of this review is to provide a background on pathogenesis and clinical presentation in HFTC, discuss current approaches to clinical management, and outline critical areas of need for future research.