Type 1 Hyperphosphatemic Familial Tumoral Calcinosis Associated With a Homozygous Variant Mutation in the GALNT3 Gene

Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare genetic disorder characterized by abnormal phosphate metabolism leading to hyperphosphatemia and calcific deposits in soft tissues. Chronic recurrent multifocal osteomyelitis (CRMO) can be challenging to diagnose and manage, especially in the context of underlying genetic conditions. This case report presents a case of a 12-year-old girl with a complex presentation involving osteomyelitis and a rare genetic disorder. This 12-year-old girl was referred by the orthopedic team for evaluation of right tibial osteomyelitis based on MRI findings. She had experienced painful swelling, redness, and increased warmth in her right thigh a month prior, which improved with a nonsteroidal anti-inflammatory drug (NSAID) (Ibuprofen) alone. She became asymptomatic without the need for antibiotics and did not have a fever or respiratory symptoms during this episode. The physical examination revealed an alert and oriented patient with no dysmorphic features. Notable findings included a scar on the right thigh from the previous surgery and multiple small lesions on the pubic area. Her height and weight were appropriate for her age. MRI suggested right tibial osteomyelitis. Laboratory studies showed hyperphosphatemia and whole exome sequencing (WES) identified HFTC type 1. The patient's presentation of right tibial osteomyelitis, initially thought to be CRMO, was ultimately explained by the diagnosis of HFTC type 1, as revealed by WES. This genetic condition, associated with hyperphosphatemia and calcific deposits, accounts for her recurrent osteomyelitis, systemic symptoms, and previous bone tumor history. Management should focus on addressing phosphate imbalances and monitoring for related complications, with input from a geneticist and a specialist in metabolic bone disorders to guide comprehensive care.