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A Clinical Guide to Inherited Metabolic Diseases. By Joel T R Clarke. (Pp 280; £16.95 paperback, £50 hardback.) Cambridge University Press, 1996. ISBN 0-521-48524-X (paperback), 0-521-48064-7 (hardback).
All paediatricians need to know about inherited metabolic diseases. For most of these conditions, diagnosis depends on the astuteness of clinicians. Though newborn screening may be extended to other metabolic disorders in the future, current programmes in most parts of the UK only detect phenylketonuria and congenital hypothyroidism. Metabolic diseases can present in a wide variety of ways, involving any system of the body. No subspecialist can completely ignore these conditions but neonatologists and general paediatricians need particularly wide knowledge. Dr Clarke’s book is an excellent introduction for paediatricians in training and will also be valuable to established consultants, as there has been dramatic recent progress in this field.
Conventional textbooks have been structured around the description of individual inborn errors. Given the number of potential defects and the range of features found in each one, this approach is of limited value to clinicians seeking a diagnosis. Dr Clarke’s “clinical guide” is based on clinical presentations, suggests appropriate investigations, and describes the commoner metabolic diseases associated with each. It is designed for the general paediatrician and is not intended to be exhaustive. Neurological, hepatic, cardiac, dysmorphic, and acute neonatal presentations are considered, along with acidosis and positive screening tests for phenylketonuria. Renal presentations (apart from renal tubular acidosis) are omitted, as are many rarer manifestations. More comprehensive diagnostic algorithms have been published by Professor Saudubray in The Metabolic and Molecular Bases of Inherited Disease (7th Ed. Edited by C R Scriver et al; New York: McGraw-Hill, 1995) but these lists, though valuable to the specialist, would be indigestible for most trainees.
Inevitably, a textbook based on clinical presentations does not give such a clear picture of each disorder as more conventional texts—but there are several of these available to complement Dr Clarke’s book. In its 280 pages, the “clinical guide” contains 63 useful tables. Some of these contain information that can be surprisingly hard to find elsewhere, such as the lists of pathological and spurious causes of organic aciduria. More flow charts might be helpful (there are only five) but they are difficult to devise, generally requiring some simplification of the clinical heterogeneity associated with each inborn error.
The principles underlying treatment are outlined in the final chapter. Details are not given as, once the diagnosis is established, patients will generally be referred to a specialist. Nevertheless, a little more advice might have been appropriate. Non-specialists remain important members of the team, especially for patients with disorders of intermediary metabolism, who require urgent admission to a local hospital during episodes of acute metabolic decompensation. Protocols for the management of such emergencies need to be devised for each patient, including an “emergency regimen” to minimise catabolism that can be started at home. It is particularly important to appreciate that subtle signs recognised by parents, such as a glazed look, can be more sensitive indicators of illness than biochemical tests.