A characteristic symptom of all individuals affected with megalocornea-Intellectual disability syndrome is a distinctive eye abnormality known as megalocornea, which is the abnormal, nonprogressive enlargement of the cornea that occurs without the presence of increased pressure within the eye (glaucoma). The cornea is the clear (transparent) outer layer of the eye and has two functions – it protects the rest of the eye from dust, germs and other harmful or irritating material and it acts as the eye’s outermost lens, bending incoming light onto the inner lens, where the light is then directed to the retina (a membranous layer of light-sensing cells in the back of the eye). The retina converts light to images, which are then transmitted to the brain. The cornea must remain clear to be able to focus incoming light. Megalocornea is present at birth (congenital) and usually affects both eyes (bilateral). Although the cornea is abnormally enlarged, it is otherwise normal in structure, curvature and thickness.
Some affected individuals have additional abnormalities affecting the eyes including underdevelopment (hypoplasia) of the colored portion of the eyes (iris), abnormal “unsteadiness” of the irises during eye movements (iridodonesis) and abnormal shaping of the eye so that it does not bend light appropriately (refractive errors).These additional eye abnormalities can potentially lead to varying degrees of visual impairment.
Other characteristic features of all individuals affected with this condition include Intellectual disability and delays in the acquisition of motor skills (psychomotor delay). Most (>80%) affected individuals also experience hypotonia. Other neurologic abnormalities may be observed, including delayed speech development, poor coordination and clumsiness, seizures, hyperactivity and Involuntary movements of the face, arms and legs (limbs) and trunk consisting of slow, continual, writhing movements (athetosis) occurring in association with more rapid, jerky movements (choreoathetoid movements).
Individuals with megalocornea-Intellectual disability syndrome may also have distinctive features in the head and face area (craniofacial region). These include microcephaly, a condition that indicates that the head circumference is smaller than would be expected for an infant’s age and sex, or macrocephaly, a condition in which there is a disproportionally Large head circumference. Additional craniofacial findings may include an unusually Prominent forehead (frontal bossing), widely spaced eyes (ocular hypertelorism), downward slanting eyelid folds (palpebral fissures), vertical skin folds between the inner corners of the eyes and the nose (epicanthal folds), widening of the top part of the nose (broad nasal bridge), a long upper lip, an abnormally small lower jaw (micrognathia), a high and narrow roof of the mouth (high arched palate) and/or unusually large and/or “cup-shaped” ears.
Rare physical malformations may also be present, including abnormally long and/or permanently flexed fingers (camptodactyly), abnormal sideways curvature of the spine (scoliosis), abnormal forward curvature of the spine (kyphosis) and heart defects. Patients have also been reported with very flexible joints (joint hyperlaxity).
Additionally, affected individuals may experience primary hypothyroidism where the thyroid gland does not produce appropriate levels of hormones. These hormones are required for many bodily functions including growth and metabolism. Some affected individuals experience Growth delays ultimately resulting in short stature. Recurrent infections have also been reported in some patients.