Learn about Neuro-Skin diseases (part 2)

Article by Master, Doctor Vu Duy Dung - Department of General Internal Medicine - Vinmec Times City International Hospital

Noonan syndrome with multiple moles is an autosomal dominant RAS (RASopathy). The incidence of this rare disease is currently unknown.

Noonan syndrome with multiple heterogeneous moles and mutations in 3 genes is responsible for about 95% of cases. 1 erroneous mutation in the PTPN11 gene on chromosome 12q24 was identified in 85% of patients. However, mutations in the RAF1 gene on chromosome 3p25.2 and the BRAF gene on chromosome 7q34 were also found in some patients.

There are no specific diagnostic criteria for Noonan syndrome with multiple moles. Noonan syndrome with multiple moles was formerly known as LEOPARD syndrome, with clinical features described for ease of remembering as: Multiple moles, abnormal cardiac electrical conduction, decreased interocular distance, valve stenosis pulmonary artery, external genital abnormalities, developmental delay, and neuro-sensory deafness.
Noonan syndrome with many moles has become a well-known name in neuro-dermatological diseases.
The clinical features of Noonan syndrome with multiple moles are highlighted in Table 1.
Table 1: Clinical features of Noonan syndrome with multiple moles

When Noonan syndrome with multiple moles is suspected, a thorough clinical evaluation and appropriate genetic testing will be performed by the geneticist to confirm the diagnosis.
Clinical examination should evaluate for concomitant neurological, cardiac, urogenital, and auditory abnormalities. Noonan syndrome with multiple moles is autosomal dominant, so genetic counseling is essential for patients and their families.
In addition, careful cardiac evaluation, including physical examination, electrocardiogram, and echocardiogram, is recommended in all patients with Noonan Syndrome with multiple juvenile-onset moles and those with Cardiac evaluation was performed repeatedly for hypertrophic cardiomyopathy, an arrhythmia that progressed over time.
In addition, newborn hearing screening should be performed in all patients. Hearing screening may need to be repeated annually as hearing loss has been reported in older ages.
To screen for the possibility of Noonan syndrome in particular and neurological - skin diseases in general, people should choose a reputable and quality medical facility for examination. Currently, at Vinmec International General Hospital, the Center for Gene Technology performs tests of molecular genetics, cell genetics, cancer genetics, etc., which can diagnose chromosomal abnormalities, genetic diseases, genetic mutations or inherited genes in antenatal screening, detection of oncogenes in some diseases, screening for cancer genes in families with genetic factors or suitable selection for resistance between donors and recipients in organ transplantation.

References: Rosser T. Neurocutaneous Disorders. Continuum (Minneap Minn) 2018;24(1, Child Neurology):96-129.