Noonan syndrome with multiple lentigines

Noonan syndrome with multiple lentigines (NSML), formerly known as LEOPARD syndrome, is a rare autosomal dominant genetic disorder belonging to the RASopathy family of conditions. The acronym LEOPARD historically described its cardinal features: Lentigines (multiple dark spots on the skin), Electrocardiographic conduction abnormalities, Ocular hypertelorism (widely spaced eyes), Pulmonary stenosis, Abnormalities of the genitalia, Retardation of growth, and sensorineural Deafness. The condition is caused primarily by mutations in the PTPN11 gene, though mutations in RAF1 and BRAF have also been identified. These genes encode proteins involved in the RAS-MAPK signaling pathway, which plays a critical role in cell growth, differentiation, and development. The disease affects multiple body systems. Cardiac involvement is a hallmark feature, with hypertrophic cardiomyopathy being the most common and clinically significant cardiac abnormality, followed by pulmonary valve stenosis and electrocardiographic abnormalities. The characteristic multiple lentigines (small, dark brown macules) typically appear during childhood and increase in number over time, often numbering in the thousands by puberty. Craniofacial features include widely spaced eyes, broad nasal root, and dysmorphic ears. Mild to moderate short stature is common, and sensorineural hearing loss of variable severity may occur. Genital anomalies, particularly cryptorchidism in males, and mild developmental delays have also been reported. There is currently no cure for NSML, and management is primarily supportive and symptom-based. Regular cardiac monitoring is essential due to the risk of progressive hypertrophic cardiomyopathy, which may require medical or surgical intervention. Hearing aids may be needed for sensorineural deafness, and growth hormone therapy may be considered for significant short stature. Genetic counseling is recommended for affected individuals and their families. Ongoing research into MEK inhibitors and other targeted therapies for RASopathies may offer future therapeutic options.

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