Noonan syndrome management and follow-up
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Serge Korjian, Yazan Daaboul
Overview
A chronic, mutlidisciplinary, system-based approach is recommended in the management and follow-up of patients with Noonan syndrome with special emphasis on the cardiac complications, growth delay, and neurocognitive deficits.
Management and Follow-up
A mutlidisciplinary team is often needed in the management of Noonan syndrome. A system-based approach is usually adopted and recommendations are based on the severity of disease manifestations.
Cardiovascular
- Patients with Noonan syndrome require lifetime cardiac follow-up. After initial evaluation including a focused cardiac physical exam, echocardiography, and electrocardiography, follow up is based on work-up findings. If initial work-up is unremarkable, a follow up is recommended every 5 years. [1][2]
- The most common cardiac finding is pulmonary valve stenosis. If mild, only periodic follow-up is recommended. If clinically significant, pulmonary balloon valvuloplasty is recommended in the absence of significant valve dysplasia. With significantly dysplastic valves a pulmonary valvectomy or pulmonary valve homograft during childhood is the first line management. [3]
- The second most common cardiac manifestation of Noonan syndrome is hypertrophic cardiomyopathy. Management is usually similar to most patients with HCM and includes beta-blockers and surgical myomectomy in certain cases with significant outflow obstruction. [3]
Endocrine and Developmental
- Up to 70% of patients with Noonan syndrome have some form of growth delay with mean delay in bone age of 2 years. Although growth hormone supplementation has only been studied in small studies, data suggests improved growth without significant side effects.
- Most studies with long-term follow up suggest that better outcomes are associated with earlier initiation of GH and a longer duration of treatment.[3]
- The largest study involving 65 patients with a mean age at initiation of 11.6 years showed a mean growth of 10.9 cm in boys vs. 9.2 cm in girls with a mean treatment duration of 5.6 years at a dose of 0.33 mg/kg/week.[4] In general, doses used in most studies ranged from 0.24-0.35 mg/kg/week.[3]
- Special growth curves for Noonan syndrome have been developed and should be used in plotting growth.[5]
- Plotting growth on curves specific for Noonan syndrome is recommended to be done 3 times yearly from birth till age 3 years than yearly after that.[1]
- Patients with growth deceleration, signs of hypothyroidism, or delayed puberty should be referred to a pediatric endocrinologist.[3]
Renal and Genitourinary
- 10% of patients with Noonan syndrome have associated renal abnormalities. Renal ultrasound is recommended at diagnosis.[3]
- Prophylactic antibiotics can be used for hydronephrosis or recurrent urinary tract infection.[3]
- Cryptorchidism can be found in up to 80% of boys with Noonan syndrome and close attention to descended testes is recommended. Surgical orchiopexy is usually required by the age of 1 year.[1][2]
Hematology
- Bleeding disorders can be seen in up to 65% of patients with Noonan syndrome.[3] An initial work-up consisting of a complete blood cell count with differential, prothrombin time and activated partial thromboplastin time is recommended.[1]
- A repeat evaluation is required if the patient was aged 6-12 months during first screening.[1]
- If the patient requires any surgical procedure, a pre-operative screen with added factor IX, XI, and XII concentration assays, von Willebrand factor, and platelet aggregation testing is recommended in conjunction with a hematology consult.[1]
Neurologic and Behavioral
- Neurologic, behavioral and cognitive abnormalities are often seen in patients with Noonan syndrome although they are poorly understood and very variable among patients.[3]
- Yearly developmental screening is recommended especially between the ages of 5 and 18 years old with individual educational plans recommended in patients with delays.[1]
- A complete neuropsychological examination is recommended if any deficits are detected on developmental screening.[3]
Gastrointestinal
Any patient with Noonan syndrome with recurrent vomiting or feeding difficulties requires a pediatric gastroenterology consultation for further investigation and management including antireflux medications, feeding tube insertion, and surgical consult in certain cases with malrotation. [3]
Eye and Ear
- A complete ophthalmologic examination is recommended at diagnosis and at least every 2 years thereafter if no problems are detected.
- A hearing test in recommended during infancy with yearly retesting in early childhood, and careful attention and management of ear infections to avoid hearing loss. [3]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Roberts AE, Allanson JE, Tartaglia M, Gelb BD (2013). "Noonan syndrome". Lancet. 381 (9863): 333–42. doi:10.1016/S0140-6736(12)61023-X. PMID 23312968.
- ↑ 2.0 2.1 van der Burgt I (2007). "Noonan syndrome". Orphanet J Rare Dis. 2: 4. doi:10.1186/1750-1172-2-4. PMC 1781428. PMID 17222357.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Romano AA, Allanson JE, Dahlgren J, Gelb BD, Hall B, Pierpont ME; et al. (2010). "Noonan syndrome: clinical features, diagnosis, and management guidelines". Pediatrics. 126 (4): 746–59. doi:10.1542/peds.2009-3207. PMID 20876176.
- ↑ Romano AA, Dana K, Bakker B, Davis DA, Hunold JJ, Jacobs J; et al. (2009). "Growth response, near-adult height, and patterns of growth and puberty in patients with noonan syndrome treated with growth hormone". J Clin Endocrinol Metab. 94 (7): 2338–44. doi:10.1210/jc.2008-2094. PMID 19401366 Check
|pmid=value (help). - ↑ Witt DR, Keena BA, Hall JG, Allanson JE (1986). "Growth curves for height in Noonan syndrome". Clin Genet. 30 (3): 150–3. PMID 3780030.
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