We report a patient with Noonan syndrome with multiple lentigines (NSML) due to a PTPN11 (p.Thr468Met) mutation associated with hypertrophic neuropathy of lumbar plexus in an adult woman, initially referred for neuropathic pain.
In in vitro assays, melanin synthesis in human melanoma cells expressing SHP-2 with LS-associated mutations was higher than in cells expressing normal SHP-2, suggesting that LS-associated SHP-2 mutations might enhance melanin synthesis in melanocytes, and that the activation of Akt/mTOR signalling may contribute to this process.
We report a typical case of LEOPARD syndrome with PTPN11 gene mutation associated with lentigines, electrocardiograph abnormality, ocular hypertelorism, pulmonary valve stenosis, growth retardation, and sensorineural hearing loss.
In conclusion, SHP2 mutations causing LS facilitate EGF-induced PI3K/AKT/GSK-3beta stimulation through impaired GAB1 dephosphorylation, resulting in deregulation of a novel signaling pathway that could be involved in LS pathology.
Our results indicate that previously enigmatic aspects of LEOPARD syndrome pathogenesis can be explained by the combined effects of loss of Shp2 catalytic function and retention of an SH2 domain-mediated role that is essential for neural crest cell survival.
We screened nine patients with ML/LEOPARD syndrome (including a mother-daughter pair) and two children with NS who had multiple café au lait spots, for mutations in the NS gene, PTPN11, and found, in 10 of 11 patients, one of two new missense mutations, in exon 7 or exon 12.