Maffucci Syndrome, Calcium Homeostasis, and Endocrine Challenges in Management

Maffucci syndrome is a rare disorder characterized by enchondromatosis and hemangiomata. It can occur due to sporadic, de novo, mosaic pathogenic variants in the gene encoding isocitrate dehydrogenase 1 (IDH1) or isocitrate dehydrogenase 2 (IDH2). IDH1 variants are associated with endocrine manifestations, such as pituitary adenomas. However, literature is limited in describing other clinical features and available treatments in severe phenotypes. We report a pediatric patient with uniquely complex and severe Maffucci syndrome. Case: A 5-year-old boy was evaluated by pediatric endocrinology for chronic hypercalcemia as part of a multidisciplinary evaluation of his severe Maffucci syndrome. Past medical history included prematurity, restrictive lung disease, developmental delay, seizures, 2-OH glutaric aciduria, angiomas, and bicytopenia. Physical exam revealed angiomas, scoliosis, and severe bony deformities throughout the entire skeleton. During admission, laboratory assays revealed normal parathyroid hormone, phosphorus, 1,25-OH2D, and C-telopeptide; elevated serum calcium and PTH-related peptide; and low 25-OHD, alkaline phosphatase, and osteocalcin. Low-dose ACTH stimulation test yielded a peak cortisol level of 16.8. A 24-hour urine study confirmed hypercalciuria. Renal ultrasound demonstrated nephrocalcinosis. Skeletal survey revealed diffuse and chondromatous changes of nearly every bone. Whole-exome sequencing detected a presumed, mosaic de novo IDH1 variant. DEXA scan revealed total body BMD z-score of -3.8. Discussion: Hypercalcemia in Maffucci syndrome is a rare phenomenon. The most likely etiology was due to the severe and chronic bony breakdown from the underlying progressive enchondromatosis. Subsequently, the body attempted to adapt to these chronic processes with abnormal mineral homeostasis, as seen in his laboratory assays. Chronic primary hyperparathyroidism was not likely, as his PTH, phosphorus, and 1,25 OH2D levels were not congruent with that diagnosis. Familial hypocalciuric hypercalcemia was not likely, as his urine calcium clearance ratio was >0.01. Finally, his slightly elevated PTHrP level was not due to PTHrP-mediated hypercalcemia of malignancy, as his bone marrow biopsy was negative. The options for short-term hypercalcemia management had their own inherent risks and were not suitable for long-term management. Although there is a lack of pediatric data to guide therapy in Maffucci syndrome, decision was made to proceed with bisphosphonate infusion given the benefits in the setting of his nephrocalcinosis, chronic hypercalcemia, and results of his DEXA scan. Given the rarity of Maffucci syndrome, few characteristics are well-described in the pediatric population. A multidisciplinary approach is necessary to review the severity of the disease and to determine the best treatment approach based on this information.