The syndrome causes cerebellar ataxia (balance and coordination problems), mental retardation, congenital cataracts in early childhood, muscle weakness, inability to chew food, thin brittle fingernails, and sparse hair.

Small stature, mild to severe mental retardation and dysarthria (slow, imprecise speech) are usually present.

Various skeletal abnormalities (e.g., curvature of the spine) and hypergonadotropic hypogonadism often occur.

Muscle weakness is progressive, but life expectancy is near normal.

The combination of muscular hypotonia and fixed dilated pupils in infancy is suspicious of Gillespie syndrome. Early onset partial aniridia, cerebellar ataxia, and mental retardation are hallmark of syndrome. The iris abnormality is specific and seems pathognomonic of Gillespie syndrome. The aniridia consisting of a superior coloboma and inferior iris hypoplasia, foveomacular dysplasia.

Atypical Gillespie syndrome associated with bilateral ptosis, exotropia, correctopia, iris hypoplasia, anterior capsular lens opacities, foveal hypoplasia, retinal vascular tortuosity, and retinal hypopigmentation.

Neurological signs ar nystagmus, mild craniofacial asymmetry, axial hypotonia, developmental delay, and mild mental retardation. Mariën P did not support the prevailing view of a global mental retardation as a cardinal feature of Gillespie syndrome but primarily reflect cerebellar induced neurobehavioral dysfunctions following disruption of the cerebrocerebellar anatomical circuitry that closely resembles the "cerebellar cognitive and affective syndrome" (CeCAS).

Congenital pulmonary stenosis and helix dysplasia can be associated.

VLDLR-associated cerebellar hypoplasia (VLDLRCH; alternative names: dysequilibrium syndrome, DES; nonprogressive cerebellar disorder with mental retardation) is a rare autosomal recessive condition caused by a disruption of the VLDLR gene. First described as a form of cerebral palsy in the 1970s, it is associated with parental consanguinity and is found in secluded communities, with a number of cases described in Hutterite families.

Diagnosis of MSS is based on clinical symptoms, magnetic resonance imaging (MRI) of the brain (cerebellar atrophy particularly involving the cerebellar vermis), and muscle biopsy.

It can be associated with mutations of the SIL1 gene, and a mutation can be found in about 50% of cases.

Differential diagnosis includes Congenital Cataracts Facial Dysmorphism Neuropathy (CCFDN), Marinesco–Sjögren like syndrome with chylomicronemia, carbohydrate deficient glycoprotein syndromes, Lowe syndrome, and mitochondrial disease.

The skin lesions evolve through characteristic stages:

1. blistering (from birth to about four months of age),

2. a wart-like rash (for several months),

3. swirling macular hyperpigmentation (from about six months of age into adulthood), followed by

4. linear hypopigmentation.

Alopecia, hypodontia, abnormal tooth shape, and dystrophic nails are observed. Some patients have retinal vascular abnormalities predisposing to retinal detachment in early childhood. Cognitive delays/mental retardation are occasionally seen.

Discolored skin is caused by excessive deposits of melanin (normal skin pigment).

Most newborns with IP will develop discolored skin within the first two weeks.

The pigmentation involves the trunk and extremities, is slate-grey, blue or brown, and is distributed in irregular marbled or wavy lines.

The discoloration sometimes fades with age.

Neurological problems can include: cerebral atrophy, the formation of small cavities in the central white matter of the brain, and the loss of neurons in the cerebellar cortex.

About 20% of children with IP will have slow motor development, muscle weakness in one or both sides of the body, mental retardation, and seizures.

They are also likely to have visual problems, which can include: crossed eyes, cataracts, and severe visual loss.

Dental problems are common, and include missing or peg-shaped teeth - patients with IP often keep milk teeth into adult life.

Breast anomalies can occur in 1% of patients; anomalies can include hypoplasia and supernumerary nipples.

Skeletal and structural anomalies can occur in approximately 14% of patients, including:

- Somatic asymmetry,

- Hemivertebrae,

- Scoliosis,

- Spina bifida,

- Syndactyly,

- Acheiria (congenital absence of the hands - note: other limbs may be affected),

- Ear anomalies,

- Extra ribs,

- Skull deformities,

- Primary pulmonary hypertension,

- Cardiopulmonary failure

Worth syndrome, also known as benign form of Worth hyperostosis corticalis generalisata with torus platinus, autosomal dominant osteosclerosis, autosomal dominant endosteal hyperostosis or Worth disease, is a rare autosomal dominant congenital disorder that is caused by a mutation in the LRP5 gene. It is characterized by increased bone density and benign bony structures on the palate.

The age of onset is in a child's infancy. Bilateral corneal opacification started in the second year of life and led to severe visual impairment. However, cornea surgery and replacement resulted in better vision.

Symptoms include a combination of spinocerebellar degeneration and corneal dystrophy. Mental retardation and slowly progressive cerebellar abnormalities were also diagnosed in patients. Other symptoms include corneal edema, thickening of Descemet membrane, and degenerative pannus. Abnormalities were found in muscle and sural nerves.

Lissencephaly 2, more commonly called Norman–Roberts syndrome, is a rare form of microlissencephaly caused by a mutation in the RELN gene.A small number of cases have been described. The syndrome was first reported by Margaret Grace Norman and M. Roberts et al. in 1976.

Lack of reelin prevents normal layering of the cerebral cortex and disrupts cognitive development. Patients have cerebellar hypoplasia and suffer from congenital lymphedema and hypotonia. The disorder is also associated with myopia, nystagmus and generalized seizures.

Norman–Roberts syndrome is one of two known disorders caused by a disruption of the reelin-signaling pathway. The other is VLDLR-associated cerebellar hypoplasia, which is caused by a mutation in the gene coding for one of the reelin receptors, VLDLR.

Disruption of the RELN gene in human patients is analogous to the malfunctioning RELN gene in the reeler mouse.

Gillespie syndrome, also called aniridia, cerebellar ataxia and mental deficiency. is a rare genetic disorder. The disorder is characterized by partial aniridia (meaning that part of the iris is missing), ataxia (motor and coordination problems), and, in most cases, intellectual disability. It is heterogeneous, inherited in either an autosomal dominant or autosomal recessive manner. Gillespie syndrome was first described by American ophthalmologist Fredrick Gillespie in 1965.

The classical triad of symptoms that defines 3C syndrome includes certain heart defects, hypoplasia (underdevelopment) of the cerebellum, and cranial dysmorphisms, which can take various forms. The heart defects and cranial dysmorphisms are heterogeneous in individuals who are all classed as having Ritscher-Schinzel syndrome.

Heart defects commonly seen with Ritscher-Schinzel syndrome are associated with the endocardial cushion and are the most important factor in determining a diagnosis. The mitral valve and tricuspid valve of the heart can be malformed, the atrioventricular canal can be complete instead of developing into the interatrial septum and interventricular septum, and conotruncal heart defects, which include tetralogy of Fallot, double outlet right ventricle, transposition of the great vessels, and hypoplastic left heart syndrome. Aortic stenosis and pulmonary stenosis have also been associated with 3C syndrome.

The cranial dysmorphisms associated with 3C syndrome are heterogeneous and include a degree of macrocephaly, a large anterior fontanel, a particularly prominent occiput and forehead, ocular hypertelorism (wide-set eyes), slanted palpebral fissures, cleft palate, a depressed nasal bridge, cleft palate with associated bifid uvula, low-set ears, micrognathia (an abnormally small jaw), brachycephaly (flattened head), and ocular coloboma. Low-set ears are the most common cranial dysmorphism seen in 3C syndrome, and ocular coloboma is the least common of the non-concurrent symptoms (cleft lip co-occurring with cleft palate is the least common).

Cranial dysplasias associated with 3C syndrome are also reflected in the brain. Besides the cerebellar hypoplasia, cysts are commonly found in the posterior cranial fossa, the ventricles and the cisterna magna are dilated/enlarged, and Dandy-Walker malformation is present. These are reflected in the developmental delays typical of the disease. 75% of children with 3C syndrome have Dandy-Walker malformation and hydrocephalus.

Signs and symptoms in other body systems are also associated with 3C syndrome. In the skeletal system, ribs may be absent, and hemivertebrae, syndactyly (fusion of fingers together), and clinodactyly (curvature of the fifth finger) may be present. In the GI and genitourinary systems, anal atresia, hypospadia (misplaced urethra), and hydronephrosis may exist. Adrenal hypoplasia and growth hormone deficiency are associated endocrine consequences of Ritscher-Schinzel syndrome. Some immunodeficiency has also been reported in connection with 3C syndrome.

Many children with the disorder die as infants due to severe congenital heart disease. The proband of Ritscher and Schinzel's original study was still alive at the age of 21.

A fetus with 3C syndrome may have an umbilical cord with one umbilical artery instead of two.

Microlissencephaly Type B or Barth microlissencephaly syndrome: is a microlissencephaly with thick cortex, severe cerebellar and brainstem hypoplasia. The Barth-type of MLIS is the most severe of all the known lissencephaly syndromes.

This phenotype consists of polyhydramnios (probably due to poor fetal swallowing), severe congenital microcephaly, weak respiratory effort, and survival for only a few hours or days. Barth described two siblings with this type as having a very low brainweight, wide ventricles, a very thin neopallium, absent corpus callosum and absent olfactory nerve.

Non-progressive congenital ataxia (NPCA) is a non-progressive form of cerebellar ataxia which can occur with or without cerebellar hypoplasia.

Microlissencephaly with mildly to moderately thick (6–8 mm) cortex, callosal agenesis

Lhermitte–Duclos disease (LDD) (), also called dysplastic gangliocytoma of the cerebellum, is a rare, slowly growing tumor of the cerebellum, a gangliocytoma sometimes considered to be a hamartoma, characterized by diffuse hypertrophy of the granular layer of the cerebellum. It is often associated with Cowden syndrome. It was described by Jacques Jean Lhermitte and P. Duclos in 1920.

Incontinentia pigmenti (IP) is a rare genetic disorder that affects the skin, hair, teeth, nails, and central nervous system. It is named from its appearance under a microscope. It is also known as Bloch–Siemens syndrome, Bloch–Sulzberger disease, Bloch–Sulzberger syndrome, melanoblastosis cutis, and nevus pigmentosus systematicus.

It is characterized by skin abnormalities that begin in childhood, usually a blistering rash which heals, followed by the development of harder skin growths. The skin may develop grey or brown patches which fade with time. Other symptoms can include hair loss, dental abnormalities, eye abnormalities that can lead to vision loss, and lined or pitted fingernails and toenails. Associated problems can include delayed development, intellectual disability, seizures, and other neurological problems. There is no specific treatment, individual conditions must be managed by specialists.

Classification systems for malformations of the cerebellum are varied and are constantly being revised as greater understanding of the underlying genetics and embryology of the disorders is uncovered. A classification proposed by Patel S in 2002 divides cerebellar malformations in two broad groups; those with cerebellar hypoplasia and; those with cerebellar dysplasia.

- I. Cerebellar hypoplasia

- A. Focal hypoplasia

- 1. Isolated vermis

- 2. One hemisphere hypoplasia

- B. Generalized hypoplasia

- 1. With enlarged fourth ventricle (“cyst,”), Dandy-Walker continuum

- 2. Normal fourth ventricle (no “cyst”)

- a. With normal pons

- b. With small pons i. Normal foliation

- a) Pontocerebellar hypoplasias of Barth, types I and II

- b) Cerebellar hypoplasias, not otherwise specified

The currently recognized features of HHS are cerebellar hypoplasia, immunodeficiency, progressive bone marrow failure, and intrauterine growth retardation. HHS patients also commonly exhibit symptoms such as microcephaly, aplastic anemia, and mental retardation.

Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome that is usually lethal in the neonatal period. Fryns (1987) reviewed the syndrome.

13q deletion syndrome is a rare genetic disease caused by the deletion of some or all of the large arm of human chromosome 13. It causes intellectual disability and congenital malformations that affect a variety of organ systems.

Corneal-cerebellar syndrome (also known as Der Kaloustian-Jarudi-Khoury syndrome) is an autosomally resessive disease that was first described in 1985. Three cases are known: all are sisters in the same family.

In addition to HHS-specific sequelae, HHS patients frequently present with the mucocutaneous triad of nail dysplasia, lacy skin pigmentation, and oral leukoplakia

Main clinical signs and symptoms include:

- headache

- movement disorders

- tremor

- visual disturbances

- abnormal EEG

- Diplopia

Patients with Lhermitte–Duclos disease and Cowden's syndrome may also have multiple growths on skin. The tumor, though benign, may cause neurological injury including abnormal movements.

MICROSCOPY(lhermitte-duclos disease)

1>Enlarged circumscribed cerebellar folia

2>internal granular layer is focally indistinct and is occupied by large ganglion cells

3>myelinated tracks in outer molecular layer

4>underlying white matter is atrophic and gliotic

Different areas of deletion are associated with different symptoms. Deletions from the centromere to 13q32 or any deletions including the 13q32 band are associated with slow growth, intellectual disability, and congenital malformations. Deletions from 13q33 to the end of the chromosome are associated with intellectual disability. Intellectual disabilities range from very mild to very severe, and can co-occur with behavioral disorders and/or autism spectrum disorders.

At birth, the main symptoms include low weight (due to intrauterine growth restriction), hypotonia, and feeding difficulties. Infants may also have cleft palate.

13q deletion syndrome gives a characteristic appearance to affected individuals, potentially including microphthalmia (small eyes), hypertelorism (wide-set eyes), thin forehead, high palate, underdeveloped midface, small mouth, small nose, broad, flat nasal bridge, short neck, low hairline, irregular or wrongly positioned teeth, low-set ears, micrognathia (small jaw), tooth enamel defects, short stature, microcephaly (small head), a prominent, long philtrum, and earlobes turned inwards.

Congenital heart disease is associated with 13q deletion syndrome. Common defects include atrial septal defect, tetralogy of Fallot, ventricular septal defect, patent ductus arteriosus, pulmonary stenosis, and coarctation of the aorta. Defects of the endocrine system, digestive system, and genitourinary system are also common. These include underdevelopment or agenesis of the pancreas, adrenal glands, thymus, gallbladder, and thyroid; Hirschsprung's disease; gastric reflux, imperforate anus, retention testis, ectopic kidney, renal agenesis, and hydronephrosis.

A variety of brain abnormalities are also associated with 13q deletion. They can include epilepsy, craniosynostosis (premature closing of the skull bones), spastic diplegia, cerebral hypotrophy, underdevelopment or agenesis of the corpus callosum, cerebellar hypoplasia, deafness, and, rarely, hydrocephalus, Dandy–Walker syndrome, and spina bifida. The eyes can be severely damaged and affected individuals may be blind. They may also have coloboma of the iris or choroid, strabismus, nystagmus, glaucoma, or cataracts.

Other skeletal malformations are found with 13q deletion syndrome, including syndactyly, clubfoot, clinodactyly, and malformations of the vertebrae and/or thumbs.

Deletions that include the 13q32 band, which contains the brain development gene ZIC2, are associated with holoprosencephaly; they are also associated with hand and foot malformations. Deletions that include the 13q14 band, which contains the tumor suppressor gene Rb, are associated with a higher risk of developing retinoblastoma, which is more common in XY children. Deletion of the 13q33.3 band is associated with hypospadias. Other genes in the potentially affected region include NUFIP1, HTR2A, PDCH8, and PCDH17.

Non-progressive early onset ataxia and poor motor learning are the commonest presentation.

Revesz syndrome is a fatal disease that causes exudative retinopathy and bone marrow failure. Other symptoms include severe aplastic anemia, intrauterine growth retardation, fine sparse hair, fine reticulate skin pigmentation, ataxia due to cerebellar hypoplasia, and cerebral calcifications. Its effects are similar to that of Hoyeraal-Hreidarsson syndrome. It is a variant of dyskeratosis congenita.