ESPE Abstracts

Introduction: ABCD syndrome is characterized by hypercalcemia, hypercalciuria, nephrocalcinosis, and renal impairment, generally under 4 years old. This is a rare cause of pediatric hypercalcemia with only 7 cases published, but it is believed to be underdiagnosed. The suspected mechanism would be associated with overexpression of transient receptor potential channels (TRP) that modulate intestinal absorption of calcium, since TRP-M2 is encoded on chromosome 21. Dietary calcium restriction would be the treatment of choice.

Clinical case: A 4-year-old male with DS, postviral lung disease, cordal paralysis with tracheostomy and feeding by nasogastric tube, was consulted to endocrinology for hypercalcemia and hyperphosphatemia He consulted the emergency room for vomiting, diarrhea and fever. He was in fair condition with general pallor. His laboratory showed anemia, impaired renal function (creatinine 3.3 mg/dl, urea 70 mg/dl), normal electrolyte panel, hypercalcemia (11.8 mg/dl), hyperphosphatemia (10 mg/dl), low PTH (4.7 pg/ml), and normal 25 (OH) vitamin D (47.4 ng/ml). Calciuria/creatininuria was elevated (0.8) and renal ultrasound showed bilateral nephrocalcinosis. He was admitted for diagnosis, ruling out oncological and infectious diseases. ABCD syndrome was suspected and he started treatment with hyperhydration, furosemide, sevelamer, aluminum hydroxide, and decreased milk intake (he was receiving 1500 ml of 15% formula per day due to poor weight gain). Renal biopsy was performed to rule out another associated renal component, and reported calcium deposits and tubulointerstitial inflammatory involvement. Despite the adequate initial response to treatment, he required 2 new hospitalizations due to hypercalcemia (up to 13.7 mg/dl) and, for this reason, he started methylprednisone 1 mg/kg/day with little response. Dairy intake was progressively reduced to an extensively hydrolyzed formula and a formula with a low calcium and phosphorus content without vitamin D, with a total of 196 mg/day of calcium. He presented good response to dietary calcium restriction (calcemia 10.2 mg/dl, phosphatemia 3.6 mg/dl and creatinine 1.8 mg/dl) that allowed progressive decrease in methylprednisone until suspension.

Conclusions: ABCD syndrome is a very rare cause of pediatric hypercalcemia. In our patient, this diagnosis was confirmed by clinical evolution and results of the renal biopsy. In patients with DS, the endocrinologist should consider the possibility of this condition, maintain an age-appropriate calcium intake, and perform a phosphocalcic profile and renal ultrasound in those with compatible symptoms or high calcium intake.