# Hyperphosphatemic Familial Tumoral Calcinosis With a Large Hip Mass

## TL;DR

A 35-year-old man with a hip mass was diagnosed with a rare genetic disorder causing abnormal phosphate levels and calcification, requiring surgery and dietary treatment.

## Contribution

This case highlights the delayed diagnosis and management challenges of hyperphosphatemic familial tumoral calcinosis in an adult patient.

## Key findings

- The patient had a pathogenic variant in the GALNT3 gene, confirming a diagnosis of hyperphosphatemic familial tumoral calcinosis.
- Surgical excision and phosphate-lowering treatment were effective in managing the calcinosis and hyperphosphatemia.
- Delayed diagnosis is common due to slow symptom progression, emphasizing the need for early awareness and genetic counseling.

## Abstract

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder that generally presents in the first two decades of life with ectopic calcification throughout the body. The underlying metabolic disorder is caused by a mutation in a gene responsible for regulating fibroblast growth factor 23 (FGF23) activity. Loss of regulation of FGF23 results in hyperphosphatemia resulting in the characteristic tissue calcinosis deposits, especially in periarticular locations. The diagnosis is made with imaging, hyperphosphatemia, and genetic testing. Medical and surgical treatments are recommended to reduce blood phosphate and remove the masses.

A 35-year-old male presented with a painful left lateral hip mass that had been gradually enlarging over the past four months. X-rays showed amorphous calcific densities in the left hip consistent with tumoral calcinosis. Magnetic resonance imaging (MRI) noted a stable complex mass in the left posterior hip and ischio-femoral space consistent with tumoral calcinosis. He had an elevated phosphorus level of 6.0 mg/dL (reference range 2.5 to 4.5 mg/dL). Excision of the mass was successful and genetic testing showed a pathogenic variant in polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3), associated with HFTC. He was treated with diet and sevelamer (phosphate binder), and discharged.

This case demonstrates that the detection of the disorder can be delayed by the slow progression of clinical symptoms and tumor calcinosis over time. Ultimately, early awareness of the disease and the mechanisms responsible for the tissue damage are important to limit long-term health consequences, which can include calcifications that ulcerate and limit joint motion. As seen in this patient, the condition often requires repeated surgical interventions. Finally, this is an autosomal recessive inherited disorder, so genetic counseling is an important component of comprehensive care.