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Metabolic bone disease
2021-03-05 12:00 AM
Also known as osteopenia of prematurity, the incidence is 32–90% in pre-term infants (mostly ELBW).
Metabolic bone disease
Also known as osteopenia of prematurity, the incidence is 32–90% in pre-term infants (mostly ELBW).
Cause
Chronic substrate deficiency—usually phosphate, rarely calcium or vita-min D. Risk is increased if:
- prolonged PN;
- breastfed (low in phosphate);
- chronic diuretic treatment.
Presentation
- Bone mineral biochemical derangement (see b Investigations); measure serum Ca2+, PO43-and alkaline phosphatase weekly in all infants under 33wks gestation.
- ‘falls’ Linear growth.
- Rib or distal long bone fractures.
Investigations
- Biochemistry: PO43-<1.2mmol/L; Ca2+ >2.7mmol/L; alkaline phosphatase >1000IU/L.
- Bone X-ray: osteoporosis, features of rickets, fractures.
- Urine Ca2+/PO43-ratio >1 after 3wks of age (high renal PO43- reabsorption).
Treatment
- Oral PO43-1mmol/kg/day supplement if milk fed.
- Increase TPN Ca2+and PO43- (consult pharmacist).
Prevention
In infants <2kg or <33wks gestation:
- Supplement breast milk with oral PO43-1mmol/kg/day (not required if fed preterm formula as already contains added PO43- );
- Oral vitamin D 400IU/day;
- Ensure TPN contains Ca2+2mmol/kg/day and PO43- 2.5mmol/kg/day (organic phosphate solution avoids mineral precipitation);
- 10min/day of passive exercise appears beneficial.
Prognosis
Stature is reduced at age 18mths. Bone mineralization and fracture risk appear to be normal by 2yrs