Singleton-Merten Syndrome

Heterogenous syndrome characterized by the association of familial aortic stenosis, calcifications of the aorta, aortic and mitral valves anomalies and osteoporosis. There is an increased globulin levels with immunologic disorders.

Merten-Singleton Syndrome.

No epidemiological studies have been reported for this very rare condition.

Thought to be autosomal dominant.

Linear calcification of the ascending aorta and severe calcific mixed aortic valve disease (stenotic and regurgitant). Associated with increased globulin levels, a lambda-chain gammopathy, and increased T4:T8 lymphocyte ratio. Histology shows extensive medial necrosis of the proximal aorta and its branches with secondary plaques of calcium confined to those areas. No evidence of previous inflammation or destructive/reparative processes.

Clinical findings consistent with aortic stenosis, possibly associated with mild regurgitation and left ventricular hypertrophy. ECG may show left ventricular hypertrophy, left axis deviation, or left bundle branch block. Radiographic examination characteristically shows severe tubular calcification of the ascending aorta and aortic valve. Cases described have not shown aortic dilatation. Echocardiographic and cardiac catheter studies may reveal the aortic stenosis and regurgitation across a tricuspid aortic valve. History, examination, and investigations must exclude other causes of aortitis and aortic calcification, for example, syphilis, arthrosclerosis, rheumatoid arthritis, and ankylosing spondylitis. Immunologic findings as above. The Singleton-Merten syndrome is also described as showing ascending aortic calcification and aortic valve disease developing in childhood, but is characterized by dental dysplasia and osteoporosis.

Cardiac murmur detected in first or second decades of life. Features of aortic stenosis and radiographic evidence of calcification seen from second decade. Progressive course with eventual need for aortic valve replacement.

Obtain full cardiac history, particularly with regard to heart failure, syncope, and chest pain. Evaluate ECG for evidence of left ventricular hypertrophy and bundle branch block. Review chest radiograph for evidence of aortic calcification, ventricular dilatation, and pulmonary congestion. Echocardiography to assess aortic valve gradient and left ventricular function. Review cardiac catheter studies if available.

Those pertinent to aortic stenosis and/or regurgitation. Bacterial endocarditis prophylaxis necessary.

Caution with use of intravenous induction agents in presence of decreased cardiac output. Circulation time may be prolonged. Avoid excessive decreases in systemic vascular resistance in presence of relatively fixed cardiac output across a stenotic valve.

Calcific Aortic Stenosis: A rare complication of aortic sclerosis that occurs as a consequence of aging, affecting approximately 2 to 3% of those older than 75 years of age. Narrowing of the aortic orifice because of calcification of the valvular ring. May occur in an idiopathic form without any predisposing conditions in the elderly. However, because aortic sclerosis is a common problem in the general population, the overall number of patients with calcific aortic stenosis is rather high.

Calcified Ascending Aorta: A common complication of familial hypercholesterolemia.

Williams Syndrome: A development disorder affecting vascular, connective tissue, and the central nervous system. Leads to a polymalformative syndrome with elfin-like facies, mental retardation, and supravalvular aortic stenosis. It is caused by a microdeletion in the elastin gene in the long arm of chromosome 7 (7q11.23), and can lead to a partial monosomy 7q11.23 in 26% of patients