Endocrine Abstracts

Introduction: Known to be ‘male Turner syndrome’, Noonan syndrome (NS) classically associates short stature, facial dysmorphism, and congenital heart disease. It is an autosomal dominant disease with an incidence of 1: 1,000 to 1: 2,500. We report 3 observations of NS.

Observations: Case 1: A 7-year-old female patient was admitted for a growth delay. On examination, she had a dysmorphic syndrome suggestive of NS: facial dysmorphism with triangular face, hypertelorism, low implanted ears, webbed neck, enlarged chest and small hands. Cardiac ultrasound was normal. Dynamic tests confirmed a partial GH deficiency. The causal mutation has not been identified.

Observation 2: A newborn was admitted for prematurity, intrauterine growth retardation and neonatal respiratory distress. The patient had a dysmorphic syndrome with an erased forehead, hypertelorism, low implanted ears with congenital lymphedema. NS was suspected. Cardiac echocardiography was indicated, but the child presented a cardiopulmonary arrest at the 6th day of life. A mutation of PTPN11 gene has been found.

Observation 3: A 7-year-old female patient was admitted for a stature delay. On examination, she had a dysmorphic syndrome suggestive of NS: a triangular face with curly hair, hypertelorism and low implanted ears. Cardiac ultrasound was normal. Dynamic tests confirmed a complete GH deficiency. The causal mutation has not been identified.

Discussion: The initial diagnosis of NS is based on the clinical presentation. In the neonatal period, there may be asymmetrical ptosis and the ears may be thick, wide and angulated posteriorly. As childhood progresses, the appearance of the face becomes longer and takes a more triangular shape. Asymmetric bilateral ptosis and hypertelorism become more apparent. The hair can be unusually curly. Facial features tend to normalize in late adolescence and it can be very difficult to recognize adults with NS from facial features alone. More than 80% of patients have cardiovascular abnormality. Pulmonary stenosis is the most characteristic lesion of NS. Our second patient would most likely have a cardiopulmonary malformation. Since the identification of the responsible genes, it has become possible to use genetic tests to establish the diagnosis. In some centers, testing will be limited to the PTPN11 gene, but since it can only diagnose half of the cases of NS, it is best to use a panel of genes if possible. The causal mutations are unknown in 30% to 40% of cases which was the case of the 1st and the 3rd observation.