A 3.5-month-old male 1.4 kg red ruffed lemur (Varecia rubra) was evaluated following auscultation of a grade IV/VI systolic cardiac murmur during routine neonatal examination. Echocardiography revealed a perimembranous ventricular septal defect (VSD), overriding (dextropositioned) aorta, right ventricular concentric hypertrophy and moderate pulmonic valve stenosis. There was right-to-left blood flow through the VSD. These findings are consistent with a tetralogy of Fallot with right-to-left shunting. Despite the poor prognosis associated with this disease, this patient has done relatively well for six years. To the authors' knowledge, this is the first published report of a tetralogy of Fallot in any lemur species.
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