LEOPARD syndrome is an autosomal dominant condition related to Noonan syndrome, although it occurs less frequently. The aim of this study was to characterize the clinical and molecular features of a large series of LEOPARD syndrome patients.

We collected clinical data from 19 patients in 10 hospitals. Bidirectional sequencing analysis of PTPN11, RAF1, and BRAF focused on exons carrying recurrent mutations.

After facial dysmorphism, structural heart defects (88%) were the most common feature described. Hypertrophic cardiomyopathy (71%) was diagnosed more often than pulmonary valve stenosis (35%). Multiple lentigines or café au lait spots were found in 84% of the series, and deafness was diagnosed in 3 patients. Mutations in PTPN11 were identified in 16 (84%) patients (10 patients had the recurrent LEOPARD syndrome mutation, p.Thr468Met) (NP_002825.3T468M). Two other patients had a mutation in RAF, and 1 patient had a mutation in BRAF. When compared with other neurocardiofaciocutaneous syndromes, LEOPARD syndrome patients showed a higher prevalence of hypertrophic cardiomyopathy and cutaneous abnormalities, and a lower prevalence of pulmonary valve stenosis and short stature.

LEOPARD syndrome patients display distinctive features apart from multiple lentigines, such as a higher prevalence of hypertrophic cardiomyopathy and lower prevalence of short stature. Given its clinical implications, active search for hypertrophic cardiomyopathy is warranted in Noonan syndrome spectrum patients, especially in LEOPARD syndrome patients.