The association between specific genetic mutations causing Duchenne/Becker muscular dystrophy (DBMD) and dilated cardiomyopathy (DCM) is largely unknown. We have observed variability in DCM incidence among brothers with DBMD and identical genetic defects. Purpose: to quantify variability of DCM among brothers with DBMD and identical genetic defects in our clinic.
Retrospective chart review of echocardiogram results and pulmonary function covering January 1992-March 2009. Exclusion criteria: steroid therapy or inadequate follow-up. DCM was defined by: shortening fraction (SF) < 30%. The SF of each brother was compared to his sibling at their oldest comparable age to determine if the brothers had concordant or discordant cardiac function. Pulmonary function correlations were assessed.
Among 97 patients were 6 eligible sibships; five sibships contained 2 brothers and one had 3 brothers. Mean age at SF comparisons was 20.6 years (range 15–27 yrs). In 3 of the 6 sibships, the brothers had concordant cardiac function: i.e., all brothers had DCM. In 3 sibships, the brothers had discordant cardiac function: in one sibship, only 1 of 3 brothers had DCM; in the other two, 1 of 2 brothers had DCM. Difference in SF between brothers in the discordant sibships at oldest comparable age ranged from 9% to 23%. Among brothers with discordant cardiac function, pulmonary function was concordant in one sibship and discordant in two sibships, including 2 brothers with superior pulmonary function who had the worst cardiac function. Among brothers concordant for DCM, pulmonary function was also concordant; but pulmonary function level was poor in two sibships and relatively good in one sibship.
Among the brothers in our clinic with DBMD and identical genetic mutations, variability of cardiac function was common, found in 3 of 6 sibships. There was no apparent correlation between cardiac and pulmonary function.
Our findings suggest that genetic test results alone may have limited utility for predicting cardiac function in patients with DBMD and that correlations between pulmonary function and cardiac function may be unpredictable.
Mahi Ashwath, No Financial Disclosure Information; No Product/Research Disclosure Information