Hypertrophic cardiomyopathy has been investigated mainly at referral institutions. Thus, the clinical history of the disease that emerges from published studies could be influenced by a bias in patient selection. In the present study, we compared the clinical features of an outpatient population of 25 patients who had hypertrophic cardiomyopathy with those reported in 78 studies published during the past five years. In the 25 study patients, age, sex, and the extent of left ventricular hypertrophy, as well as the prevalence of diastolic filling abnormalities, subaortic obstruction, and ventricular arrhythmias, were similar to those in patients described in the literature. Cardiac symptoms, however, were much less severe in the study patients. Eighteen patients (72 percent) were asymptomatic, six (24 percent) had mild symptoms, and only one (4 percent) had moderate-to-severe symptoms. Of 24 patients followed for a mean period of 4.4 years (range, 2.9 to 5.7), none died or had clinical deterioration. Of 3404 patients described in the 78 studies we reviewed, 2483 (73 percent) came from only two referral institutions. Of the 1721 patients in whom severity of symptoms was reported, 757 (44 percent) had moderate-to-severe symptoms. However, 727 (96 percent) of these patients were studied at one of the same two referral institutions. We conclude that the natural history of hypertrophic cardiomyopathy may be more benign than can be inferred from published reports.

Surveys of performing musicians indicate that almost half of them experience playing-related medical problems, some of which threaten or end their careers. Overuse injuries involving the muscle--tendon unit are the most common problem, with symptoms ranging from mild pain while the musician is playing to pain severe enough to preclude any use of the affected hand. String players are the most commonly affected, and percussionists the least. The most important predisposing characteristic is the use of repetitive movements during long hours of practice, but awkward body positions mandated by the shape and weight of the instrument, the technical difficulty of the repertoire, and unfamiliar instruments may also play a part. Women are more commonly affected than men. Rest is the cornerstone of therapy. Neural impingement syndromes affecting the median or ulnar nerves or the thoracic outlet affect many musicians. Focal dystonias may involve part or all of a hand or the muscles forming the embouchure (the position of the lips in wind players). These are very resistant to therapy and may terminate or drastically alter a career. Stress, especially performance anxiety, may impede performance. Beta-adrenergic blocking agents prevent the symptoms of performance anxiety and are frequently used by musicians without medical supervision. A recognition of the unique problems of musician-patients has led to the formation of successful specialty clinics in a number of cities.

In the past 10 years considerable progress has been made in the diagnosis of hereditary disorders at the DNA level. Many monogenic disorders can now be examined at the gene level; such examination has led to a better understanding of the molecular basis of these disorders and made carrier detection and prenatal diagnosis possible. Each year, more and more monogenic disorders can be added to the list of diseases that can be diagnosed by DNA analysis. Future research will be devoted to the identification of genes responsible for other known monogenic hereditary disorders, the elucidation of the molecular lesion associated with chromosomal abnormalities, and the characterization of the genes and gene defects involved in the common multifactorial diseases. The goal of diagnosis is the identification of the genetic defect in affected patients, persons destined to be affected, and carriers.

This article has analyzed the pathogenesis of sodium and water retention in several circumstances. The initiator of retention has been proposed to be either a fall in cardiac output (e.g., low-output cardiac failure and vasoconstrictor hypovolemic nephrotic syndrome) or peripheral arterial vasodilatation (e.g., high-output cardiac failure, cirrhosis, arteriovenous fistula, and pregnancy). In the only state discussed, in which the kidney is diseased and not merely responding to extrarenal reflexes--i.e., nephrotic syndrome--intrarenal mechanisms may predominate and lead to expansion of the arterial vascular tree and suppression of the renin-angiotensin-aldosterone system (i.e., hypervolemic nephrotic syndrome). Otherwise, when kidneys are healthy, either a fall in cardiac output or peripheral arterial vasodilatation may diminish arterial vascular filling and thereby initiate a series of hemodynamic and hormonal events that result in renal sodium and water retention (Fig. 7). Finally, the approach presented in this article should be considered to be a vantage point from which to evaluate states of sodium and water retention, but not to be an exclusive position.