Nutritional hypophosphatemic rickets secondary to Neocate® use

Elemental formula is commonly used in children with feeding intolerance. We describe two, medically complex and feeding tube dependent, patients exclusively fed with Neocate® who subsequently developed hypophosphatemic rickets. Both patients had gross motor decline and pain with physical touch. They were found to have low serum phosphorus, normal calcium, and vitamin D studies, with elevated alkaline phosphatase suggestive of nutritional hypophosphatemia. Both courses were complicated by hypocalcemia following formula change and phosphorus supplementation, highlighting the need for careful management of phosphate repletion in affected individuals. Diligent serial electrolyte monitoring as well as attention to bone health is needed in conjunction with elemental nutrition. Formula change led to restoration of calcium and phosphorus homeostasis and radiographic improvement in these patients.

A pediatric hypophosphatemic rickets on MRI, 99mTc-MDP bone scan and 18F-FDG PET/CT

We present a case of a 13 years old boy who was hospitalized with a 10 months history of progressive pain and weakness in his lower extremities. The laboratory tests revealed slightly decreased phosphate and 25-hydroxyvitamin D3, high alkaline phosphatase, normal calcium and parathyroid hormone (PTH). Magnetic resonance imaging (MRI) showed multiple patchy lesions indicating bone destruction in the metaphyses and epiphyses of the left knee. Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) revealed a generalized decrease of bone density in axial bones with slightly increased ¹⁸F-FDG metabolism. Whole body technetium-99m methylene diphosphonate (^99mTc-MDP) scintigraphy revealed multiple areas of increased uptake at costochondral junctions of the ribs bilaterally suggesting a rachitic rosary and at the metaphyses of the bones of the limbs. Based on these findings we suggested the diagnosis of hypophosphatemic rickets (HPR). Phosphate and vitamin D substitution resulted in clinical improvement of the symptoms after 3 months.

[Medical treatment of children with hypophosphataemic rickets]

Hypophosphataemic rickets is a rare, genetic disorder resulting in defect bone mineralisation and rickets. The current medical treatment consists of phosphate supplementation and alfacalcidol, but side effects such as secondary hyperparat-hyroidism and nephrocalcinosis are common. This treatment regimen often fails to prevent bone deformity and reduced final height. The rarity and complexity of these diseases call for centralised specialist care and international collaboration. Future medical treatment may be improved by addition of new promising experimental treatments.