mental retardation

Small testes and gynecomastia are found in males while females have oligo- or amenorrhea.  The hands and feet appear broad and the face has a coarse appearance with a depressed nasal bridge and a broad nose.  Insulin-resistant diabetes and hyperinsulinemia are present.  Acanthosis nigricans, keloids, obesity, and hearing loss are also features.  All patients have significant developmental delays and evident mental retardation.

The clinical diagnosis of Canavan disease is suggested when the triad of hypotonia, macrocephaly and head lag is present.  It is a progressive form of spongy degeneration of the central nervous system but its onset, course, and severity are variable.

The disease is often evident before 6 months of age and survival is limited to a few months or years in infants with such early onset.  Such patients have the most severe and rapidly progressive disease.  It is noteworthy that, even though such infants do not achieve normal milestones such as sitting and standing, they do often interact socially by laughing, smiling, and reaching for objects.  Most young children are quiet and apathetic but some become irritable and develop spasticity as they grow.  CNS damage is evident as leukodystrophy on neuroimaging studies but this may not be present in later onset, milder forms of the disease.         

Other individuals may have a later and milder juvenile onset of symptoms and may present with delayed speech or motor development late in the first decade.  They often attend regular school but may benefit from tutoring and speech therapy.  They may live to adolescence or early adulthood.  Maldevelopment of the organ of Corti is responsible for hearing deficits in some children.

This is a highly complex dysmorphic developmental disorder with unusual progression of facial features.  Birth weight and length are usually normal but later there is general somatic and mental growth delay with microcephaly (pre- and post natal), short stature, intellectual disability, and epilepsy (70%).  Hypotonia has been noted at birth.  A significant proportion (~50%) of patients have Hirschsprung disease with megacolon.  Congenital heart defects are common, many involving septal openings.  Hypospadias is often present with or without other genitourinary anomalies.  Teeth are often crowded and crooked.  The earlobes may be flattened and may have a central depression.

The facial features are present in early childhood but as they mature the upper half of the nasal profile becomes convex, while the nasal tip becomes longer and overhangs the philtrum.  The eyes appear more deeply set.  The chin lengthens and prognathism becomes apparent.  IQ levels cannot be determined but many individuals exhibit behavioral or emotional disturbances.

A wide variety of systemic anomalies have been reported.  Congenital heart defects (primarily septal) and CNS malformations are among the most common features, reported in 85% and 55% respectively.  Tetralogy of Fallot is considered by some to be the most common heart malformation.  Growth and mental retardation are found in nearly 100%.  The pinnae are often set low and hearing loss is common.  Ear anomalies, both internal and external, have been described in 91%, and some degree of conduction and/or sensorineural deafness is present in 62%.  Choanal atresia is found in at least 57% of patients.  This along with cleft palate and sometimes esophageal atresia or reflux often contributes to feeding difficulties which are common in all age groups.  Cranial nerve deficits are seen in 92% of patients and more than one nerve is involved in nearly 3 of 4 patients.  The most common cranial nerve defects involve numbers IX, X, VIII, and V.  Facial palsies are an especially important feature. Hypogonadotropic hypogonadism and underdevelopment of the external genitalia are often seen, especially in males.  One-third of patients have limb anomalies and many have short digits.  The facies is considered by some as characteristic with a square configuration, broad forehead, flat midface, and a broad nasal bridge.

Infant and childhood morbidity is high with feeding difficulties a major cause of death.

This is a disorder of glycosylation important to the formation of glycoproteins and glycolipids.  Neurological signs such as tremor, clonus, and muscle fasiculations may be seen soon after birth.  Other neurological abnormalities eventually include psychomotor retardation, seizures, mental retardation, hyperexcitabilty, and ataxia.  Failure to thrive and feeding difficulties are evident early.  Progressive microcephaly is a feature.  Liver dysfunction can lead to coagulopathy and hypoproteinemia with hepatomegaly is sometimes present.  Some patients have facial anomalies, inverted nipples, and subcutaneous fat pads.  The MRI may show areas of brain atrophy, ischemia, and focal necrosis.

Longevity is limited with 2 of 3 reported patients dying within 2 years of life.

The systemic features reported include severe global delay, a broad nasal bridge, and short stature.  Physical growth delay, mental retardation, short neck, low-set ears, and low posterior hairline have been noted.  Males may have a micropenis and undescended testicles.  The pinnae may be malformed and rotated posteriorly. Several patients had a hearing deficit.

CT scans have shown microcephaly with pachygyria and or even virtual agyria of the frontal, temporal, and parietal lobes.