Myocardial disarray in Noonan syndrome.

OBJECTIVE

To characterise the histopathology of the left ventricular hypertrophy commonly associated with Noonan syndrome by assessing the extent of myocyte disarray and therefore to define one aspect of the relation between this disease and idiopathic hypertrophic cardiomyopathy.

DESIGN

Blinded histological analysis.

SETTING

Hospital medical school.

PATIENTS

Six hearts of children with the Noonan phenotype and isolated ventricular hypertrophy were compared with age and sex matched controls.

METHODS

Histological analysis was performed with an image analyser under light microscopy. Representative sections from the entire left ventricular free wall were examined. Results were expressed as the percentage of fields showing disarray related to the number of fields evaluated: 100 fields were examined for each patient.

RESULTS

In the patients with Noonan syndrome myocardial disarray was present in the ventricular septum in 24 (5.7)% (mean (SD)) of fields and in the free wall in 22.2 (6.8)%. In the controls disarray was present in the septum in 3.8 (2.3)% of fields and in the free wall in 2.4 (2.8)%. In both regions the extent of disarray was significantly greater in patients with Noonan syndrome (p < 0.0005; 95% confidence interval 14 to 26.3 for the septum: p < 0.005, 95% confidence interval 11.4 to 28.2 for the free wall).

CONCLUSIONS

The ventricular hypertrophy associated with Noonan syndrome is histologically similar to hypertrophic cardiomyopathy but whether the two diseases are the expression of the same genetic defect remains to be determined.