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Histological findings in non-hypertrophic cardiomyopathy associated with Noonan’s syndrome
  1. N CARY
  1. S LARGE
  1. Senior Lecturer in Cardiology,
  2. Guy’s and St Thomas Hospitals,
  3. London, UK
  4. Consultant Histopathologist,
  5. Papworth Hospital,
  6. Cambridge, UK
  7. Consultant Transplant Surgeon,
  8. Papworth Hospital

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Sir,—We have reported the clinical and echocardiographic findings in a family with Noonan’s syndrome and a non-hypertrophic cardiomyopathy with restrictive physiology.1 The original proband has now had cardiac transplantation and we are able to report the histological findings. There was extensive, patchy fibrosis with many areas of myocyte disarray. There was also variability in the size of the myocytes with many hypertrophied cells. There were small foci of inflammatory cells, mainly monocytes, but with eosinophils in some areas. Perls’s stain for haemosiderin and Congo red stain for amyloid were normal.

In about 25% of cases, Noonan’s syndrome is associated with hypertrophic cardio- myopathy,2 which is characterised histologically by increased myocyte disarray.3 However, there are a few cases of cardiomyopathy where the histological findings of fibre hypertrophy without disarray have been more suggestive of primary restrictive myopathy.4 In our case the histological findings were unusual. There was myocyte disarray, but the degree of fibrosis was greater than usually seen in hypertrophic cardiomyopathy and there were intramyocardial eosinophils raising the possibility of Loeffler’s carditis. At no time was the peripheral blood eosinophil count raised, there were no echocardiographic features of endocardial disease, and there was reduced left ventricular systolic function on echocardiography that was out of keeping with Loeffler’s endocarditis, but consistent with primary restrictive cardiomyopathy.

In the absence of histological changes of primary restrictive myopathy or of infiltrative disease, the likeliest diagnosis is hypertrophic cardiomyopathy without hypertrophy as described by McKenna et al.5 Our case is atypical in the echocardiographic findings as well as histology. Whether it is clinically useful to continue classifying such cases under the unitary diagnosis of a condition already known to have a wide phenotypic and genetic makeup6 remains to be seen.