Bone Abstracts (2017) 6 P048 | DOI: 10.1530/boneabs.6.P048

A rare cause of rickets

Sophia Sakka1, Suma Uday1, Tabitha Randell2, Justin H Davies3, Ved Bushan Arya4, Caroline Brain4, Jeremy Allgrove4, Wolfgang Högler1,5 & Nick J Shaw1,5

1Department of Endocrinology and Diabetes, Birmingham Children’s Hospital, Birmingham, UK; 2Department of Paediatric Endocrinology and Diabetes, Nottingham Children’s Hospital, Nottingham, UK; 3Department of Endocrinology and Diabetes, University Hospital Southampton, Southampton, UK; 4Department of Paediatric Endocrinology, Great Ormond Street Hospital, London, UK; 5Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK.

Background: The development of hypophosphataemic rickets in infants fed with the elemental formula (EF) Neocate® has been recently reported. We present seven cases of exclusively Neocate-fed babies who developed hypophosphataemic rickets.

Presenting problem: Three patients (P1,3,4) had incidental findings of rickets on chest X-rays, two (P2,6) developed leg deformities and rickets was confirmed on X-rays, and two (P5,6) presented with femur fractures. Patient 7 was found to have low phosphate concentrations on routine blood testing and was further investigated. All patients (age 5 months – 3.2 years) were exclusively fed on Neocate at presentation and had normal serum calcium and parathyroid hormone concentrations, raised alkaline phosphatase and hypophosphataemia. Vitamin D deficiency and renal phosphate wasting were excluded (Table 1).

Clinical management: Following exclusion of other causes of rickets, reduced intestinal phosphate absorption due to EF was considered. Patients 1–6 were treated with phosphate supplements after diagnosis of rickets. Patient 6 was previously on long term steroids and received one course of bisphosphonates after the fracture. Formula was changed eventually in all patients and phosphate concentrations normalized after 1 week-4 months. Clinical and/or radiological improvement of rickets was noted in P2,3,4. No X-ray confirmation of improvement is available so far in the others.

Table 1 Clinical and biochemical characteristics of patients.
Patient 1Patient 2Patient 3Patient 4Patient 5Patient 6Patient 7
Gestational age31w27w33w39w+331wterm34w+4
DiagnosisPresumed cow’s milk allergyGORD, cow’s milk intolerancePierre-Robin Syndrome, cleft palate, CP, GORD, NJ fedCHARGE syndrome, GORD, PEG fedFTT, GORD, PEG-NJ fedSCID, BMT, GVHD on steroids, refusing feedSOD, GORD, 8q12.3del, tectal plate glioma, NJ fed
Age at presentation6 months10 months11 months18 months9 months3 years 2 m5 months
Exclusively on Neocate before presentation (duration)3 months10 months>8 months>6 months5 months15 months5 months
Phosphate (mmol/L)1.230.680.831.040.841.340.63
ALP (IU/L)10001000346943116534192206
PTH (ng/L)2419.8175.62131Normal
25-OH-VitaminD (nmol/L)59.7868834776131110
TRP (%)99.599.8>97NANANA
Abbreviations: GORD: gastro-oesophageal reflux disease; CP: cerebral palsy; NJ: naso-jejunal; PEG: percutaneous endoscopic gastrostomy; FTT: failure to thrive; SCID: severe combined immunodeficiency; BMT: bone marrow transplant; GVHD: graft versus host disease; SOD: septo-optic dysplasia;.NA: not available.

Discussion: The fact that serum phosphate improved following weaning of Neocate supports its role in the causation of hypophosphataemia; poor intestinal absorption of phosphate is the assumed mechanism in infants exclusively fed with Neocate. Clinicians should exercise caution in the use of EF in the absence of clear clinical indications. Infants who are being exclusively fed on Neocate should have close clinical and biochemical monitoring of bone profile, in accordance with existing guidance.

Disclosure: The authors declared no competing interests.

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