Familial dilated cardiomyopathy of young Portuguese Water Dogs

A novel dilated cardiomyopathy (DCM) in 12 related Portuguese Water Dogs wa s identified by retrospective analysis of postmortem and biopsy case record s. Male and female puppies born to clinically healthy parents typically die d at 13 (+/- 7.3) weeks of age (range, 2-32 weeks) because of congestive he art failure. Puppies died suddenly without previous signs or with mild depr ession followed by clinical signs of congestive heart failure 1-5 days befo re death. There was no sex predilection. The hearts were enlarged and round ed, with marked left ventricular and atrial dilation. No other significant structural cardiac defects were noted. The histologic changes in the myocar dium were diffuse and characterized by myofibers of irregular sizes separat ed by an edematous interstitium. The myofibers had multifocal swollen, clea red segments often involving perinuclear areas that contained granular, pho sphotungstic-acid-hematoxylin-positive material consistent with mitochondri a. There was loss of the cross-striation pattern, and intercalated discs we re difficult to identify. There was no evidence of concurrent myocardial fi brosis; rare chronic inflammatory infiltrates were noted in one dog. Noncar diac skeletal muscles were not affected. The underlying cause is unknown. F rom the pedigree analysis, an autosomal recessive pattern of inheritance is suspected. Based on the histologic findings, this DCM is most likely due t o an underlying molecular (biochemical or structural) defect. The early ons et and rapid progression of the disease makes this a clinically distinctive form of canine DCM.