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Myotonic dystrophy, 3rd edition: major problems in neurology series, No 37
  1. D Hilton-Jones

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    By Peter S Harper (Pp 436, £55.00). Published by W B Saunders, London, 2001. ISBN 0 7020 2152 0

    This is the third edition of Peter Harper's exemplary monograph, and it has been much awaited. Myotonic dystrophy transcends virtually all medical disciplines and few clinicians will not find something of value to their own practice. Every neurologist and geneticist with frequent involvement with such patients should have a personal copy, and for the rest there should be copies in departmental and postgraduate libraries. It has been written in a style that also makes it accessible to some patients and their families and I recently met an American with the condition who takes her copy of the second edition to every clinical consultation, often to the benefit of her physician!

    It is extraordinary to recollect the enormous advances that have been made in our understanding of the condition since the second edition, published in 1989. This is partly reflected in an increase in size of some 50 pages, despite omission of significant sections from the previous edition. The isolation of the gene in 1992 has revolutionised our diagnostic approach, and gone are the days of slit lamp examination and neurophysiological studies to identify gene carriers. The genetic basis, an unstable trinucleotide repeat expansion, is now known to be common to several neurological disorders and whole meetings are now devoted to “unstable DNA”. The past few years have seen the evolution of theories to explain how such a mutation, in an untranslated region of a gene, can lead to the protean manifestations of the disease. For this third edition, Harper has sought the collaboration of David Brook and Emma Newman who have contributed a chapter on the molecular and cell biology of myotonic dystrophy. One proposed mechanism to explain the widespread consequences of the condition is that there is disruption of RNA metabolism. The clinical similarities with proximal myotonic myopathy (PROMM), a condition which had not been recognised at the time of the last edition, suggested a common mechanism and indeed, very shortly after Harper's book went to press the genetic abnormality causing PROMM was identified, and found to be a quadruplet repeat expansion in the zinc finger protein gene.

    The book is uniformly good, but I must select three chapters for special mention. The complexities of genetic counselling for this particular disorder are immense, and anybody offering such a service must read the relevant chapter. Some who currently offer “counselling” might well decide that they shouldn't! There is an excellent chapter on the disease in infancy and childhood, which is a must for paediatricians. The final chapter, on management and therapy, summarises the experience of a very experienced clinician.