Page 16 - Clinical variability in Noonan syndrome with emphasison ear and eye

CHAPTER 1
Acute leukaemia and myeloproliferative disorders are described in Noonan syndrome and the incidence is slightly higher than in the general population. The presenting types during childhood include acute lymphoblastic leukaemia (ALL), juvenile myelomonocytic leukaemia (JMML), lymphoma, neuroblastoma, and rhabdomyo- sarcoma. An earlier onset and milder presentation of JMML in Noonan syndrome is described (57,58).
Ocular abnormalities
Ocular anomalies are seen frequently in Noonan syndrome. Face dysmorphology is part of the clinical scoring system and include external ocular abnormalities. Most frequent external ocular anomalies include hypertelorism, ptosis, epicanthic folds, and downslanting palpebral fissures. Other ocular manifestations are found during ophthalmologic examinations. The first cohort of ocular manifestations in Noonan syndrome is described in 1992 with ophthalmologic examinations in 58 patients (59). Their examination revealed strabismus, refractive errors, amblyopia, and nystagmus. Anterior segment anomalies consisted of prominent corneal nerves and cataracts. Posterior segment anomalies included optic disc hypoplasia and myelinated nerves. Few other small cohort studies have been performed afterwards (60,61). Studies on visual-motor integration in Noonan syndrome show different results varying from delayed coordination to average visual-motor abilities in Noonan syndrome children (39,62).
Hearing impairment
Hearing impairment in Noonan syndrome is mentioned for the first time in 1976 (63). In a Noonan syndrome cohort of 146 patients, hearing impairment is described in 40% (14). Another cohort studied 40 ears and found a sensorineural hearing impairment in 50% of the ears (64). The sensorineural impairment is in approximately 10% found in the low frequency range and 25% in the high frequency range (64). Conducted hearing impairment is mostly secondary to recurrent otitis media. Inner ear structural abnormalities, including temporal bone abnormalities, have occasionally been reported (65).
Other features
Feeding difficulties and failure to thrive during infancy are described in 76% of the Noonan patients (14). Described problems are poor suckling, refusal to eat and drink, recurrent vomiting, gastro-esophageal reflux and constipation. Feeding problems appear to be the result of delayed gastro-intestinal motor development (66).
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