1101 - A Rare Pediatric Case of Hyperphosphatemic Familial Tumoral Calcinosis Disguised as Chronic Recurrent Multifocal Osteomyelitis

Case Diagnosis: Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare autosomal recessive disorder characterized by abnormal phosphate regulation, causing ectopic calcifications in periarticular soft tissues, leading to pain, limited mobility, and disability. FGF2, GALNT3, and KL mutations disrupt FGF23 hormone function, elevating phosphate reabsorption. Management focuses on reducing phosphate levels, pain relief, mobility improvement, and calcification removal.

Case Description: An 11-year-old male with chronic recurrent multifocal osteomyelitis (CRMO) presented with worsening pain in his left forearm/elbow. Physical examination revealed point tenderness at the right mid-radial shaft with no swelling. X-rays showed lobular mineralization in the right olecranon fossa and sclerotic lesions in the mid/proximal right ulna. MRI displayed a new calcified mass in the right olecranon fossa with marrow/periosteal edema in the right distal humerus.



Laboratory findings included elevated phosphorus (8.1 mg/dL), alkaline phosphatase (153 U/L), 1,25-dihydroxyvitamin D3 (85.6 mg/dL), and 25-hydroxyvitamin D3 (38 mg/dL). The erythrocyte sedimentation rate (ESR) was elevated at 17 mm/hr, while serum calcium was near the upper limit (9.8 mg/dL). Creatinine (0.7 mg/dL) and parathyroid hormone (PTH) (27 pg/dL) were within range, and the complete blood count (CBC) was normal.



Based on clinical, radiographic, and laboratory findings, hyperphosphatemic familial tumoral calcinosis (HFTC) was suspected. Genetic testing showed a homozygous GALNT3 mutation, confirming HFTC.

Discussions: This case underscores how HFTC is a rare but important mimicker of CRMO based on similar phenotypical features.

Conclusions: Further research is needed to explore how HFTC can present as CRMO. To enable early intervention, clinicians should remain vigilant for signs of HFTC, including elevated phosphate levels, in children with CRMO. Further, an interdisciplinary treatment approach is essential, with a physiatrist playing a crucial role in addressing activity modification to enhance mobility and improve overall patient outcomes.