A Patient with Noonan Syndrome with a KRAS Mutation Who Presented Severe Nerve Root Hypertrophy

We report a 45-year-old female with clinical features resembling Noonan syndrome (NS) who presented with significant nerve root hypertrophy. She was initially diagnosed with Charcot-Marie-Tooth disease because her gait disturbance gradually deteriorated and nerve conduction velocity was reduced. However, she did not carry a <i>PMP22</i> gene mutation. RASopathies are a group of phenotypically overlapping developmental syndromes caused by germline mutations that encode components of the Ras/MAPK signaling pathway. These disorders include NS, cardiofaciocutaneous (CFC) syndrome, and Costello syndrome and are associated with molecular abnormalities in the Ras/MAPK pathway. The patient was suspected to have NS and related disorders because of pulmonary artery stenosis, lymphedema, distinctive facial appearance, and intellectual disability. Genetic analysis identified a heterozygous de novo mutation in <i>KRAS</i> (c.211T&#x3e;G, p.Tyr71Asp), which is usually observed in patients with NS or CFC syndrome. Although our patient was diagnosed with NS, she revealed clinical manifestations that were typical to CFC syndrome, including intellectual disability. It has been reported that some patients diagnosed with RASopathies with mutations in <i>PTPN11</i>, <i>SOS1</i>, or <i>KRAS</i> developed nerve root hypertrophy. These results suggest that nerve root hypertrophy may be associated with RASopathy, although the onset mechanisms of nerve root hypertrophy are unknown.

Anesthetic Management of a Pediatric Patient With Cardiofaciocutaneous Syndrome

Cardiofaciocutaneous (CFC) syndrome is a rare condition characterized by congenital heart disease, craniofacial dysmorphology, and dermatological abnormalities. CFC syndrome is one of the RASopathies, a family of syndromes that also includes Noonan and Costello syndromes, all with underlying gene mutations involving the Ras/mitogen-activated protein kinase pathways. Important considerations for anesthesiologists caring for these patients include the need to evaluate for possible cardiac defects, anticipating and planning for potentially difficult airway management, and the consideration of potential weakness of the respiratory muscles. Musculoskeletal abnormalities, such as muscle weakness and decreased muscle mass, are observed in all RASopathies, but are particularly prominent in CFC syndrome. In patients with CFC syndrome who experience respiratory muscle weakness, the use of desflurane and remifentanil may aid in a faster recovery and effectively help reduce the risk of respiratory complications, such as respiratory depression, following general anesthesia because of their rapid metabolism or elimination.

C-type natriuretic peptide improves growth retardation in a mouse model of cardio-facio-cutaneous syndrome

Cardio-facio-cutaneous (CFC) syndrome, a genetic disorder caused by germline mutations in BRAF, KRAS, MAP2K1 and MAP2K2, is characterized by growth retardation, heart defects, dysmorphic facial appearance and dermatologic abnormalities. We have previously reported that knock-in mice expressing the CFC syndrome-associated mutation, Braf Q241R, showed growth retardation because of gastrointestinal dysfunction. However, other factors associated with growth retardation, including chondrogenesis and endocrinological profile, have not been examined. Here, we show that 3- and 4-week-old BrafQ241R/+ mice have decreased body weight and length, as well as reduced growth plate width in the proximal tibiae. Furthermore, proliferative and hypertrophic chondrocyte zones of the growth plate were reduced in BrafQ241R/+ mice compared with Braf+/+ mice. Immunohistological analysis revealed that extracellular signal-regulated kinase (ERK) activation was enhanced in hypertrophic chondrocytes in BrafQ241R/+ mice. In accordance with growth retardation and reduced growth plate width, decreased serum levels of insulin-like growth factor 1 (IGF-1) and IGF binding protein 3 (IGFBP-3) were observed in BrafQ241R/+ mice at 3 and 4 weeks of age. Treatment with C-type natriuretic peptide (CNP), a stimulator of endochondral bone growth and a potent inhibitor of the FGFR3-RAF1-MEK/ERK signaling, increased body and tail lengths in Braf+/+ and BrafQ241R/+ mice. In conclusion, ERK activation in chondrocytes and low serum IGF-1/IGFBP-3 levels could be associated with the growth retardation observed in BrafQ241R/+ mice. Our data also suggest that CNP is a potential therapeutic target in CFC syndrome.