micrognathia

Infants are usually born with a normal head circumference but fall behind (2 SD or more) in the first year.  They have neonatal and infantile central hypotonia with brisk peripheral tendon reflexes during early childhood.  They are sometimes described as drowsy or lethargic.  Facial and limb edema can be extensive but transient sometimes and can disappear later in childhood.  The fingers are tapered.  The cheeks are full, the mouth is usually open and the upper lip appears 'tented'.  Global developmental delay is common and normal milestones are seldom attained.  Some patients have been described as severely retarded mentally.  Infantile spasms and myoclonic jerkingcan be seen within the first months of life while frank seizures with hypsarrhythmia are common in the first year of life.  Status epilepticus is a common occurrence.  General drowsiness and poor feeding are often features.  Death usually occurs in infancy or early childhood.  Midface hypoplasia and micrognathia are often present.

Brain imaging (MRI) and histology show severe alterations in myelination and cellular organization.  Neuronal loss is seen in the inner granular layer of the cerebellum but there is relative preservation of Purkinje cells.  General and progressive atrophy of the cerebellum and brain stem have been described.

There is both intrauterine and postnatal growth retardation.  Hypotonia is often noted along with general psychomotor delays.  Neonatal respiratory distress and laryngeal stridor may be present.  The intellectual disability can be severe.  Corpus callosum aplasia and hypoplasia have been reported.  Microcephaly and brachycephaly with delayed suture closure are features.  The face is long and narrow and the mouth is disproportionally large.  A high arched palate can be present and the pinnae are often deformed, posteriorly rotated and may be accompanied by preauricular skin tags. The teeth appear widely spaced (diastema) and the lower jaw is underdeveloped.

Infants are born with low birth weight due to intrauterine growth retardation and there is often a history of oligohydramnios.  Newborns are often floppy and hypotonic although spasticity may develop later.  A small midface and microcephaly (80%) with a sloping forehead and a flat occiput are frequently evident.  The ears are large, floppy, and low-set while the hard palate is highly arched and the degree of micrognathia can be severe.  The fists are often clenched and the digits can appear narrow and arachnodactylous.  Hiatal hernias may be present.

Many patients develop features of the nephrotic syndrome in the first year of life with proteinuria and hypoalbuminemia due to glomerular kidney disease and renal system malformations.  Renal biopsies show focal segmental glomerulosclerosis in the majority of glomeruli.

Evidence of abnormal neuronal migration with brain deformities such as cystic changes, porencephaly, encephalomalacia, and spinal canal anomalies have been reported.  MRI imaging shows diffuse cortical and cerebellar atrophy atrophic optic nerves, and thinning of the corpus callosum.  The normal striated layers of the lateral geniculate nuclei are obliterated.  The cerebellum shows severe cellular disorganization with profound depletion of granule cells and excessive Bergmann gliosis.  The vermis is shortened. 

Multifocal seizures are sometimes (40%) seen in infancy and early childhood and the EEG generally shows slowed and disorganized backgound and sometimes a high-voltage hypsarrhythmia.  The degree of psychomotor delay and intellectual disability is often severe.   Most patients are unable to sit independently (90%), ambulate (90%), or make purposeful hand movements (77%).  The majority (87%) of children have extrapyramidal movements and a combination of axial dystonia and limb chorea.  Mean age of death is about 11 years (2.7 to 28 years in one series) and most die from renal failure.

Intrauterine growth retardation is common and infants are born with significant deformities including microcephaly, limb malformations, flexion deformities, ichthyosis, and edema of the hands and feet.   Brain malformations may be present as well.

This is a lethal dysplasia-malformation syndrome in which some infants are stillborn while others do not live beyond a few days.  The placenta is often small and the umbilical cord is short.  Decreased fetal movements and polyhydramnios are often noted.  Microcephaly can be striking at birth but there is overall intrauterine growth retardation.  The skin is ichthyotic and dysplastic containing excess fatty tissue beneath the epidermis.  Digits are often small and may be fused (syndactyly).  There is generalized edema with ‘puffiness’ of the hands and feet.  The lungs are frequently underdeveloped and cardiac defects such as septal openings, patent ductus arteriosus and transposition of great vessels are common.  Males often have cryptorchidism while females have a bifid uterus and renal dysgenesis has been reported.

The face is dysmorphic with prominent globes (in spite of microphthalmia), the ears are large and malformed, the forehead is sloping, the nose is flattened and the jaw is small.  Some infants have a cleft lip and palate while the mouth is round and gaping.  The neck is usually short.

Severe brain malformations such as lissencephaly, cerebellar hypoplasia, and dysgenesis/agenesis of the corpus callosum are frequently present.

Failure of both membranous and long bones to grow properly lead to a variety of abnormalities such as craniosynostosis, hypomelia, syndactyly, oligodactyly, malar hypoplasia, short neck, micrognathia, and cleft lip and palate.  The long bones of the limbs may be underdeveloped or even absent.  Contractures of elbow, knee, and ankle joints are common as are digital anomalies.  Low birth weight and slow postnatal growth rates are usually result in short stature.  The hair is often sparse and light-colored. 

Mental development is impaired and some children are diagnosed to have mental retardation.  Cardiac defects are common.  Facial hemangiomas are often present as are septal defects and sometimes a patent ductus arteriosus.  External genitalia in both sexes appear enlarged.  The kidneys may be polycystic or horseshoe-shaped.