โ Scribed by Winston W.K. Koo
No coin nor oath required. For personal study only.
PEDIATRIC LABORATORY MEDICINE CONGRESS drug exposure. It is frequently, but not always, associated with abnormal mineral homeostasis. Heritable MBD manifesting in infancy occurs rarely and usually represents the most severe form of the disorder. In contrast, non-genetic factors, particularly nutritional factors, are responsible more frequently for MBD in infants and can occur in all races and geographic regions. Assessment of MBD in infants depends on the family history of metabolic, endocrine or bone disorders; maternal illness and drug therapy; and the infant's postnatal course, including drug and nutritional history. Physical features associated with specific underlying disease; for example, cranial nerve palsies in congenital osteopetrosis, may be present. Specific skeletal deformities, including secondary deformities from weight bearing, may not be obvious in younger infants. Non-specific symptoms and signs, including failure to thrive, may be present.
Serial growth measurements are helpful in the diagnosis and management of MBD Laboratory investigations include standard skeletal radiographic films to demonstrate the presence and extent of involvement with respect to osteosclerosis, osteopenia and morphologic changes in the affected regions. Some radiographic changes such as osteogenesis imperfecta, rickets, hyperparathyroidism, etc., have typical appearances which can lead to conftrmatory laboratory measurements. Laboratory determination of acid-base status, renal function, liver function, vitamin D metabolites and parathyroid hormone, and indices of mineral (e.g. calcium, phosphorus) and trace metal (e.g. copper) nutritional status are useful to conftrm or rule out many of the secondary causes of MBD. Measurement of mineral homeostasis and bone turnover, including serum concentrations of calcium, magnesium, phosphorus, alkaline phosphatase, and osteocalcin; urine excretion of calcium, phosphorus and hydroxyproline, when measured serially, offer the prospect for early diagnosis and monitoring for effectiveness of therapeutic intervention. Other more recently available laboratory determinations of biochemical markers of bone turnover such as procollagen type 1 C-terminal peptide, bone-specific alkaline phosphatase and deoxypyridinoline, when used in combination with existing laboratory assessment, provide a rapid and sensitive tool to monitor acute changes in bone turnover and to better assess the pathogenesis and management of MBD in infants.
Recent adaptation of dual energy x-ray absorptiometry techniques provides an accurate and precise noninvasive direct measurement of bone mineralization in infants, and specific molecular genetic studies are additional tools that are Useful for the understanding of pathogenesis and management of MBD in infants.
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