Most of the signs and symptoms of the Joubert syndrome appear very early in infancy with most children showing delays in gross motor milestones. Although other signs and symptoms vary widely from individual to individual, they generally fall under the hallmark of cerebellum involvement or in this case, lack thereof. Consequently, the most common features include ataxia (lack of muscle control), hyperpnea (abnormal breathing patterns), sleep apnea, abnormal eye and tongue movements, and hypotonia in early childhood. Other malformations such as polydactyly (extra fingers and toes), cleft lip or palate, tongue abnormalities, and seizures may also occur. Developmental delays, including cognitive, are always present to some degree.

Those suffering from this syndrome often exhibit specific facial features such as a broad forehead, arched eyebrows, ptosis (droopy eyelids), hypertelorism (widely spaced eyes), low-set ears and a triangle shaped mouth. Additionally, this disease can include a broad range of other abnormalities to other organ systems such as retinal dystrophy, kidney diseases, liver diseases, skeletal deformities and endocrine (hormonal) problems.

Joubert syndrome is a rare autosomal recessive genetic disorder that affects the cerebellum, an area of the brain that controls balance and coordination.

Joubert syndrome is one of the many genetic syndromes associated with syndromic retinitis pigmentosa. The syndrome was first identified in 1969 by pediatric neurologist Marie Joubert in Montreal, Quebec, Canada, while working at the Montreal Neurological Institute and McGill University.

There are many signs and symptoms of Prader–Willi syndrome. The symptoms can range from poor muscle tone during infancy to behavioral problems in early childhood. Some symptoms that are usually found in infants, besides poor muscle tone, would be a lack of eye coordination; some are born with almond-shaped eyes; and due to poor muscle tone the infant may not have a strong sucking reflex. Their cry is weak, and they have difficulty waking up. Another sign of this condition is a thin upper lip.

More aspects seen in a clinical overview include hypotonia and abnormal neurologic function, hypogonadism, developmental and cognitive delays, hyperphagia and obesity, short stature, and behavioral and psychiatric disturbances.

Holm "et al." (1993) describe the following features and signs as pretest indicators of PWS, although not all will be present.

It is characterized by developmental defects including cryptophthalmos (where the eyelids fail to separate in each eye), and malformations in the genitals (such as micropenis, cryptorchidism or clitoromegaly). Congenital malformations of the nose, ears, larynx and renal system, as well as mental retardation, manifest occasionally. Syndactyly (fused fingers or toes) has also been noted.

There is an overlap in symptoms between 3C syndrome and Joubert syndrome. Joubert syndrome often manifests with similar cerebellar hypoplasia and its sequelae, including hyperpnea, ataxia, changes in eye movement, and cleft lip and palate. Occasionally, Joubert syndrome will include heart malformations. Brachmann-de Lange syndrome must also be differentiated from 3C syndrome. It presents with similar craniofacial and heart abnormalities and can include Dandy-Walker phenotype, making it difficult to distinguish. Dandy-Walker malformation is also occasionally seen in Ellis-van Creveld syndrome, which is characterized by heart defects and malformed alveolar ridge. Many disorders include the Dandy-Walker phenotype and thus it is not pathognomonic for 3C syndrome.

CHARGE syndrome can also be misdiagnosed. This is because both CHARGE syndrome and 3C syndrome share symptoms of ocular colobomas, cardiac defects, growth retardation, and minor facial abnormalities.

Coffin-Siris syndrome presents with fifth-finger deformities and congenital heart defects. It is distinguished from 3C syndrome by differences in facial dysmorphisms.

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.

Individuals with PWS are at risk of learning and attention difficulties. Curfs and Fryns (1992) conducted research into the varying degrees of learning disability found in PWS. Their results, using a measure of IQ, were as follows:

- 5%: IQ above 85 (high to low average intelligence)

- 27%: IQ 70–85 (borderline intellectual functioning)

- 39%: IQ 50–70 (mild intellectual disability)

- 27%: IQ 35–50 (moderate intellectual disability)

- 1%: IQ 20–35 (severe intellectual disability)

- <1%: IQ <20 (profound intellectual disability)

Cassidy found that 40% of individuals with PWS have borderline/low average intelligence, a figure higher than the 32% found in Curfs and Fryns' study. However, both studies suggest that most individuals (50–65%) fall within the mild/borderline/low average intelligence range.

Children with PWS show an unusual cognitive profile. They are often strong in visual organization and perception, including reading and vocabulary, but their spoken language (sometimes affected by hypernasality) is generally poorer than their comprehension. A marked skill in completing jigsaw puzzles has been noted, but this may be an effect of increased practice.

Auditory information processing and sequential processing are relatively poor, as are arithmetic and writing skills, visual and auditory short-term memory and auditory attention span. These sometimes improve with age, but deficits in these areas remain throughout adulthood.

There may be an association with psychosis.

Fraser syndrome (also known as Meyer-Schwickerath's syndrome, Fraser-François syndrome, or Ullrich-Feichtiger syndrome) is an autosomal recessive congenital disorder. Fraser syndrome is named for the geneticist George R. Fraser, who first described the syndrome in 1962.

While inclusion criteria for Rud syndrome have varied considerably, the major manifestations includes congenital ichthyosis, hypogonadism, small stature, mental retardation, and epilepsy. Ocular findings were inconsistently reported and included strabismus, blepharoptosis, blepharospasm, glaucoma, cataract, nystagmus, and retinitis pigmentosa. Other systemic includes metabolic, bony, neurologic, and muscular abnormalities.

The musculoskeletal manifestations of Proteus syndrome are frequent and recognizable. Patients tend to demonstrate a unique pattern of skeletal abnormalities. The orthopaedic features are usually bilateral, asymmetrical, progressive and involving all four limbs and spine. Afflicted patients usually have localized periarticular limb distortions, limb length discrepancy, and spine deformity. Patients with Proteus syndrome can have regular bone configuration and contours despite the bone enlargement. Patients can also exhibit hyperthyroidism of the skull and facial abnormalities. Because of the rarity of the syndrome and the variability of signs, the orthopaedic management should be individualized.

Affected individuals commonly suffer from photophobia, nystagmus and achromatopsia. Other symptoms affecting vision may include night vision difficulties; optic disc pallor; narrow vessels; macular atrophy with pigment mottling; peripheral deep white dot deposits or retinal pigment epithelium (RPE) alterations in the inferonasal retina; decreased foveal and retinal thickness; attenuation of retinal lamination; hyperreflectivity in the choroids (due to RPE and choriocapillaris atrophy); impairment of color vision; and progressive loss of vision with advancing age.

In line with ameleogenesis imperfecta, affected members may display teeth yellow-brown in colour, dysplastic, presenting numerous caries; reduced enamel layer prone to posteruptive failure; and abnormality of morphology involving dentine.

Proteus syndrome causes an overgrowth of skin, bones, muscles, fatty tissues, and blood and lymphatic vessels.

Proteus syndrome is a progressive condition wherein children are usually born without any obvious deformities. Tumors of skin and bone growths appear as they age typically in early childhood. The musculoskeletal manifestations are cardinal for the diagnosis of Proteus syndrome. The severity and locations of these various asymmetrical growths vary greatly but typically the skull, one or more limbs, and soles of the feet will be affected. There is a risk of premature death in affected individuals due to deep vein thrombosis and pulmonary embolism caused by the vessel malformations that are associated with this disorder. Because of carrying excess weight and enlarged limbs, arthritis and muscle pain may also be symptoms — as is the case for Mandy Sellars, a woman who has been diagnosed with a form of Proteus syndrome (but see "Notable Cases" below). Further risks may occur due to the mass of extra tissue.

The disorder itself does not uniformly cause learning impairments: the distribution of intelligence deficits among sufferers of Proteus syndrome appears higher than that of the general population, although this is difficult to determine with statistical significance. In addition, the presence of visible deformity may have a negative effect on the social experiences of the sufferer, causing cognitive and social deficits.

Afflicted individuals are at increased risk for developing certain tumors including unilateral Ovarian cystadenomas, testicular tumors, meningiomas, and monomorphic adenomas of the parotid gland.

Hemimegalencephaly is often found to be associated.

Rud syndrome is a poorly characterized disorder, probably of X-linked recessive inheritance, named after Einar Rud who described 2 patients with the case in 1927 and 1929. It was argued that all reported cases of Rud syndrome are genetically heterogeneous and significantly differ from the original case reports of Rud and that the designation Rud syndrome should be eliminated and that the patients with such diagnosis should be reassigned to other syndromes, such as Refsum disease and Sjögren-Larsson syndrome.Some consider Rud syndrome and Sjögren-Larsson syndrome the same entity and that Rud syndrome doesn't exist.

Jalili syndrome is a genetic disorder characterized by the combination of cone-rod dystrophy of the retina and amelogenesis imperfecta. It was characterized in 1988 by Dr. I. K. Jalili and Dr. N. J. D. Smith, following the examination of 29 members of an inbred, Arab family living within the Gaza Strip.

Most patients with ML IV show psychomotor retardation (i.e., delayed development of movement and coordination), corneal opacity, retinal degeneration and other ophthalmological abnormalities. Other symptoms include agenesis of the corpus callosum, iron deficiency resulting from an absence of acid secretion in the stomach, achlorhydria. Achlorhydria in these patients results in an increase in blood gastrin levels. These symptoms typically manifest early in life (within the first year). After disease onset there occurs a period of stability, typically lasting two to three decades during which very little disease progression occurs.

Typically, the signs and symptoms of juvenile nephronophthisis are limited to the kidneys. They include polyuria, polydipsia, weakness, and fatigue.

Anemia, growth retardation, no hypertension.

Proteinuria and hematuria are usually absent. Polyuria is resistant to vasopressin.

When other organ systems are affected, symptoms can include situs inversus, heart abnormalities, and liver fibrosis. Juvenile nephronophthisis can also be associated with other rare disorders, including Senior–Løken syndrome and Joubert syndrome.

Mucolipidosis type IV (ML IV or ML4) is an autosomal recessive lysosomal storage disorder. Individuals with the disorder have many symptoms including delayed psychomotor development and various ocular aberrations. The disorder is caused by mutations in the MCOLN1 gene, which encodes a non-selective cation channel, mucolipin1. These mutations disrupt cellular functions and lead to a neurodevelopmental disorder through an unknown mechanism. Researchers dispute the physiological role of the protein product and which ion it transports.

Infants with this condition have disproportionately short arms and legs with extra folds of skin. Other signs of the disorder include a narrow chest, small ribs, underdeveloped lungs, and an enlarged head with a large forehead and prominent, wide-spaced eyes.

Thanatophoric dysplasia is a lethal skeletal dysplasia divided into two subtypes. Type I is characterized by extreme rhizomelia, bowed long bones, narrow thorax, a relatively large head, normal trunk length and absent cloverleaf skull. The spine shows platyspondyly, the cranium has a short base, and, frequently, the foramen magnum is decreased in size. The forehead is prominent, and hypertelorism and a saddle nose may be present. Hands and feet are normal, but fingers are short. Type II is characterized by short, straight long bones and cloverleaf skull.

It presents with typical telephone handled shaped long bones and a H-shaped vertebrae.

Juvenile nephronophthisis causes fibrosis and scarring of the kidneys, which accounts for the symptoms observed. The kidneys also often have corticomedullary cysts.

- Inability to conserve sodium because of defect of tubules leading to polyuria and polydipsia.

- Anemia is attributed to a deficiency of erythropoietin production by failing kidneys.

- Growth retardation, malaise and pallor are secondary to anemia.

- No hypertension as nephronophthisis is a salt-losing enteropathy.

Infants with type 1 thanatophoric dysplasia also have curved thigh bones, flattened bones of the spine (platyspondyly) and shortened thoracic ribs. Note: Prenatal ultra-sound images of the ribs sometimes appear asymmetrical when in fact they are not. In certain cases, this has caused a misdiagnosis of Osteogenisis Imperfecta (OI) type II.

An unusual head shape called kleeblattschädel ("cloverleaf skull") can be seen with type 2 thanatophoric dysplasia.

The term congenital refers to a condition present from birth (not acquired) and amaurosis refers to a loss of vision "not" associated with a lesion. However, beyond these general descriptions, the presentation of LCA can vary, because it is associated with multiple genes.

LCA is typically characterized by nystagmus, sluggish or absent pupillary responses, and severe vision loss or blindness.

Pulmonary hypoplasia is incomplete development of the lungs, resulting in an abnormally low number or size of bronchopulmonary segments or alveoli. A congenital malformation, it most often occurs secondary to other fetal abnormalities that interfere with normal development of the lungs. Primary (idiopathic) pulmonary hypoplasia is rare and usually not associated with other maternal or fetal abnormalities.

Incidence of pulmonary hypoplasia ranges from 9–11 per 10,000 live births and 14 per 10,000 births. Pulmonary hypoplasia is a relatively common cause of neonatal death. It also is a common finding in stillbirths, although not regarded as a cause of these.

Leber's congenital amaurosis (LCA) is a rare inherited eye disease that appears at birth or in the first few months of life.

One form of LCA was successfully treated with gene therapy in 2008.

It affects about 1 in 40,000 newborns. LCA was first described by Theodor Leber in the 19th century. It should not be confused with Leber's hereditary optic neuropathy, which is a different disease also described by Theodor Leber.

The signs and symptoms of POEMS syndrome are highly variable. This often leads to long delays (e.g. 13–18 months) between the onset of initial symptoms and diagnosis. In addition to the signs and symptoms indicated by the POEMS acronym, the PEST acronym is used to describe some of the other signs and symptoms of the disease. PEST stands for Papilledema, evidence of Extravascular volume overload (ascites, pleural effusion, pericardial effusion, and lower extremity edema), Sclerotic bone lesions, and Thrombocytosis/erythrocytosis (i.e. increased in blood platelets and red blood cells). Other features of the disease include a tendency toward leukocytosis, blood clot formation, abnormal lung function (restrictive lung disease, pulmonary hypertension, and impaired lung diffusion capacity), very high blood levels of the cytokine vascular endothelial growth factor (VEGF), and an overlap with the signs and symptoms of multicentric Castleman disease.

Locked-in syndrome usually results from quadriplegia and the inability to speak in otherwise cognitively intact individuals. Those with locked-in syndrome may be able to communicate with others through coded messages by blinking or moving their eyes, which are often not affected by the paralysis. The symptoms are similar to those of sleep paralysis. Patients who have locked-in syndrome are conscious and aware, with no loss of cognitive function. They can sometimes retain proprioception and sensation throughout their bodies. Some patients may have the ability to move certain facial muscles, and most often some or all of the extraocular muscles. Individuals with the syndrome lack coordination between breathing and voice. This prevents them producing voluntary sounds, though the vocal cords are not paralysed.