Individuals with this syndrome typically develop normally until reaching the second decade of their lives but the onset of symptoms has been observed as early as age seven. The first defect observed in individuals who suffer from this condition affects the auditory system and is known as bilateral nerve deafness. Another early symptom is the development of myopia (nearsightedness). In addition to bilateral nerve deafness and myopia, other symptoms that plague infected individuals early in disease progression include ataxia, muscle wasting, severe peripheral neuritic pain sometimes accompanied by elevated spinal fluid protein, and joint stiffness.

The central nervous system (CNS) is affected with deficits in the cerebral cortex which indicate signs of mental retardation even though psychological observations appear relatively normal for individuals studied. Atypical epilepsy is also a common feature of CNS malfunctioning including aphasia expressions, blurred vision, and numbness of the face and limbs.

In the third decade of the condition, individuals develop further visual problems including retinitis pigmentosa, and bilateral cataracts. Sufferers endure the restriction of visual fields, night blindness, and eventually severe or complete blindness.

Individuals with this syndrome exhibit many physical deformities including skeletal, epidermal, and subcutaneous abnormalities. The skeletal problems are characterized by scoliosis and muscle weakness indicative of the kyphoscoliotic type which follow muscle wasting and peripheral neuritis (nerve inflammation). Osteoporosis is also observed in many cases. Skin and subcutaneous atrophy is common as well as skin ulcerations due to inability of the skin to heal. One of the final manifestations of disease is baldness.There is no evidence that the progression of Flynn–Aird syndrome shortens the patient's life-span, but the terrible conditions certainly increase morbidity.

This syndrome consists a number of typical features. These include

- Agenesis of the corpus callosum (80-99% patients)

- Hypopigmentation of the eyes and hair (80-99% patients)

- Cardiomyopathy (80-99% patients)

- Combined immunodeficiency (80-99% patients)

- Muscular hypotonia (80-99% patients)

- Abnormality of retinal pigmentation (80-99% patients)

- Recurrent chest infections (80-99% patients)

- Abnormal EEG (80-99% patients)

- Intellectual disability (80-99% patients)

- Cataracts (75%)

- Seizures (65%)

- Renal abnormalities (15%)

Infections of the gastrointestinal and urinary tracts are common. Swallowing and feeding difficulties early on may result in a failure to thrive. Optic nerve hypoplasia, nystagmus and photophobia may occur. Facial dysmorphism (cleft lip/palate and micrognathia) and syndactyly may be present. Sensorineural hearing loss may also be present.

Death in infancy is not uncommon and is usually due to cardiac complications or severe infections.

Flynn–Aird syndrome is a rare, hereditary, neurological disease that is inherited in an autosomal dominant fashion. The syndrome involves defects in the nervous, auditory, skeletal, visual, and endocrine systems and encompasses numerous symptoms, bearing striking similarity to other known syndromes of neuroectodermal nature such as: Werner syndrome, Cockayne syndrome and Refsum syndrome.

The onset of Flynn–Aird syndrome typically occurs between ten and twenty years of age, however, the earliest case was diagnosed at age seven. As the syndrome progresses, initial symptoms tend to intensify and new symptoms become apparent. Unlike related syndromes and despite the intensity of symptoms in the disease progression, Flynn–Aird syndrome does not appear to shorten life expectancy.

The disease is characterized by early-onset dementia, ataxia, muscle wasting, skin atrophy, and eye abnormalities. In addition, patients have the potential of developing a number of other related symptoms such as: cataracts, retinitis pigmentosa, myopia (nearsightedness), dental caries, peripheral neuropathy (peripheral nerve damage), deafness, and cystic bone changes. This syndrome was first discovered in the early 1950s by American neurologists P. Flynn and Robert B. Aird who analyzed one family lineage inheritance pattern of this disease.

Oculocerebrorenal syndrome (also called Lowe syndrome) is a rare X-linked recessive disorder characterized by congenital cataracts, hypotonia, intellectual disability, proximal tubular acidosis, aminoaciduria, and low-molecular-weight proteinuria. Lowe syndrome can be considered a cause of Fanconi syndrome (bicarbonaturia, renal tubular acidosis, potassium loss, and sodium loss).

This includes Ataxia-telegiectasia, Chédiak-Higashi syndrome, DiGeorge syndrome, Griscelli syndrome and Marinesco-Sjogren syndrome.

Because oculocerebrorenal syndrome is an X-linked recessive condition, the disease develops mostly in men with very rare occurrences in women, while women are carriers of the disease; it has an estimated prevalence of 1 in 500,000 people. Boys with Lowe syndrome are born with cataracts in both eyes, glaucoma is present in about half of the individuals with Lowe syndrome, though usually not at birth. While not present at birth, many affected boys develop kidney problems at about one year of age. Renal pathology is characterized by an abnormal loss of certain substances into the urine, including bicarbonate, sodium, potassium, amino acids, organic acids, albumin, calcium and L-carnitine, this problem, is known as Fanconi-type renal tubular dysfunction.

Lightwood–Albright syndrome is a form of renal tubular acidosis.

It is also known as Lightwood syndrome.

It is named for Reginald Cyril Lightwood and Fuller Albright.

The age of onset is almost always before 3 months of age. Many infants are born preterm (1/3 cases) and dysmature. The babies are frequently small for dates. The placenta may be abnormal with non-specific inflammation on histology. Umbilical cord anomalies have occasionally been reported. In severe cases, signs in the brain may be detected on prenatal ultrasound.

The presentation is pleiomorphic, making the diagnosis difficult, but the most common features of this disease involve the skin, joints, and central nervous system.

All have a maculopapular urticarial skin rash that is often present at birth (75% cases). It is probably more correctly described as an urticarial-like rash. The presence of the rash varies with time, and biopsy of these skin lesions shows a perivascular inflammatory infiltrate including granulocytes.

In about 35-65% of cases, arthritis occurs. Joint signs are variably expressed and can lead to transient swelling without sequelae between crises, or to unpredictable anomalies of growth cartilage and long bones epiphyses suggestive of a pseudo-tumour. Biopsies reveal hypertrophic cartilage without inflammatory cells. This most commonly affects the large joints (knees, ankles, elbows, and wrists) but may also involve the small joints of the hands and feet. It is usually bilateral and painful. A common and characteristic feature is giant kneecaps. Severe cases may result in contractures (joint deformities).

Most patients eventually have neurological problems. These manifest themselves in three principal ways: chronic meningitis, involvement of both the optic tract and eye, and sensorineural hearing loss. The chronic meningitis presents with the features of chronically raised intracranial pressure: headaches, vomiting, ventriculomegaly, hydrocephalus, macromegaly, cerebral atrophy, and optic atrophy. Some of these features may be evidenced on prenatal ultrasound. In 50% of cases, intellectual deficit occurs. Seizures occur in 25% of cases, but other manifestations are rare. Histological examination shows infiltration of the meninges with polymorphs.

Ocular manifestations occur in 80% of cases and include uveitis (70%), papillary involvement, conjunctivitis, and optical neuritis. If untreated, these may result in blindness (25%). The sensorineural hearing loss occurs in 75%, and tends to be progressive leading to deafness in 20% of cases.

Almost all children are remarkably short and have growth delay. Fever is extremely common but inconstant and is most often mild. Anemia is frequent. Other findings that have been reported include macrocephaly (95%), large fontanelle, prominent forehead, flattening of the nasal bridge (saddleback nose), short and thick extremities, and finger clubbing. The liver and/or spleen may be enlarged. Lymph node enlargement may also be present.

Later in life, secondary amyloidosis may occur. Delayed puberty and secondary amenorrhoea are not uncommon. Hoarseness due to inflammation of the laryngeal cartilage has also been reported.

In contrast to Hartnup disease and related tubular conditions, Fanconi syndrome affects the transport of many different substances, so is not considered to be a defect in a specific channel, but a more general defect in the function of the proximal tubules.

Different diseases underlie Fanconi syndrome; they can be inherited, congenital, or acquired.

Zellweger syndrome is one of three peroxisome biogenesis disorders which belong to the Zellweger spectrum of peroxisome biogenesis disorders (PBD-ZSD). The other two disorders are neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD). Although all have a similar molecular basis for disease, Zellweger syndrome is the most severe of these three disorders.

Zellweger syndrome is associated with impaired neuronal migration, neuronal positioning, and brain development. In addition, individuals with Zellweger syndrome can show a reduction in central nervous system (CNS) myelin (particularly cerebral), which is referred to as hypomyelination. Myelin is critical for normal CNS functions, and in this regard, serves to insulate nerve fibers in the brain. Patients can also show postdevelopmental sensorineuronal degeneration that leads to a progressive loss of hearing and vision.

Zellweger syndrome can also affect the function of many other organ systems. Patients can show craniofacial abnormalities (such as a high forehead, hypoplastic supraorbital ridges, epicanthal folds, midface hypoplasia, and a large fontanel), hepatomegaly (enlarged liver), chondrodysplasia punctata (punctate calcification of the cartilage in specific regions of the body), eye abnormalities, and renal cysts. Newborns may present with profound hypotonia (low muscle tone), seizures, apnea, and an inability to eat.

Although genetic testing positively identifies nearly two thirds of children with CHARGE syndrome, diagnosis is still largely clinical. The following signs were originally identified in children with this syndrome, but are no longer used in to make the diagnosis alone.

- C - Coloboma of the eye, central nervous system anomalies

- H - Heart defects

- A - Atresia of the choanae

- R - Retardation of growth and/or development

- G - Genital and/or urinary defects (Hypogonadism, undescended testicles, besides hypospadias.)

- E - Ear anomalies and/or deafness and abnormally bowl-shaped and concave ears, known as "lop ears".

CHARGE syndrome (formerly known as CHARGE association), is a rare syndrome caused by a genetic disorder. First described in 1979, the acronym "CHARGE" came into use for newborn children with the congenital features of coloboma of the eye, heart defects, atresia of the nasal choanae, retardation of growth and/or development, genital and/or urinary abnormalities, and ear abnormalities and deafness. These features are no longer used in making a diagnosis of CHARGE syndrome, but the name remains. About two thirds of cases are due to a CHD7 mutation. CHARGE syndrome occurs only in 0.1–1.2 per 10,000 live births; as of 2009 it was the leading cause of congenital deafblindness in the US.

The clinical features of proximal renal tubular acidosis are:

- Polyuria, polydipsia and dehydration

- Hypophosphatemic rickets (in children) and osteomalacia (in adults)

- Growth failure

- Acidosis

- Hypokalemia

- Hyperchloremia

Other features of the generalized proximal tubular dysfunction of the Fanconi syndrome are:

- Hypophosphatemia/hyperphosphaturia

- Glycosuria

- Proteinuria/aminoaciduria

- Hyperuricosuria

MPS III is characterized by severe deterioration of the central nervous system, resulting in a variety of symptoms. Individuals with Sanfilippo syndrome usually start to show the symptoms between the age of 2 to 6. Speech problems, hyperactivity, aggressive behavior, developmental delays, hirsutism, sleep disturbances, seizures are the common manifestation of the syndrome at the initial stage. After the age of 10, patients start to experience increasingly severe symptoms including loss of motor and cognitive skills and somatic diseases. Patients later enter vegetative state, eventually leading to death in their 30s.

Individuals with MPS III tend to have mild skeletal abnormalities; osteonecrosis of the femoral head may be present in patients with the severe form. Optical nerve atrophy, deafness, otitis can be seen in moderate to severe individuals. Other characteristics include coarse facial features, thick lips, synophrys, and stiff joints. Chronic diarrhea, enlarged liver and spleen are also common.

It is difficult to clinically distinguish differences among the four types of Sanflippo syndrome. However, MPS IIIA is usually the most severe subtype, characterized by earliest onset, rapid clinical progression with severe symptoms, and short survival.

The common symptoms in all reported cases of primrose syndrome include ossified pinnae, learning disabilities or mental retardation, hearing problems, movement disorders (ataxia, paralysis, and parkinsonism among others (likely due, in part, to calcification of the basal ganglia), a torus palatinus (a neoplasm on the mouth's hard palate), muscle atrophy, and distorted facial features. Other symptoms usually occur, different in each case, but it is unknown whether or not these symptoms are caused by the same disease.

Theoretically, a mutation in any of the may cause disease, but below are some notable ones, with short description of symptoms:

- Adrenoleukodystrophy; leads to progressive brain damage, failure of the adrenal glands and eventually death.

- Alport syndrome; glomerulonephritis, endstage kidney disease, and hearing loss.

- Androgen insensitivity syndrome; variable degrees of undervirilization and/or infertility in XY persons of either gender

- Barth syndrome; metabolism distortion, delayed motor skills, stamina deficiency, hypotonia, chronic fatigue, delayed growth, cardiomyopathy, and compromised immune system.

- Blue cone monochromacy; low vision acuity, color blindness, photophobia, infantile nystagmus.

- Centronuclear myopathy; where cell nuclei are abnormally located in skeletal muscle cells. In CNM the nuclei are located at a position in the center of the cell, instead of their normal location at the periphery.

- Charcot–Marie–Tooth disease (CMTX2-3); disorder of nerves (neuropathy) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs but also in the hands and arms in the advanced stages of disease.

- Coffin–Lowry syndrome; severe mental retardation sometimes associated with abnormalities of growth, cardiac abnormalities, kyphoscoliosis as well as auditory and visual abnormalities.

- Fabry disease; A lysosomal storage disease causing anhidrosis, fatigue, angiokeratomas, burning extremity pain and ocular involvement.

- Hunter's Syndrome; potentially causing hearing loss, thickening of the heart valves leading to a decline in cardiac function, obstructive airway disease, sleep apnea, and enlargement of the liver and spleen.

- Hypohidrotic ectodermal dysplasia, presenting with hypohidrosis, hypotrichosis, hypodontia

- Kabuki syndrome; multiple congenital anomalies and mental retardation.

- Spinal and bulbar muscular atrophy; muscle cramps and progressive weakness

- Lesch-Nyhan syndrome; neurologic dysfunction, cognitive and behavioral disturbances including self-mutilation, and uric acid overproduction (hyperuricemia)

- Lowe Syndrome; hydrophthalmia, cataracts, intellectual disabilities, aminoaciduria, reduced renal ammonia production and vitamin D-resistant rickets

- Menkes disease; sparse and coarse hair, growth failure, and deterioration of the nervous system

- Nasodigitoacoustic syndrome; mishaped nose, brachydactyly of the distal phalanges, sensorineural deafness

- Nonsyndromic deafness; hearing loss

- Norrie disease; cataracts, leukocoria along with other developmental issues in the eye

- Occipital horn syndrome; deformations in the skeleton

- Ocular albinism; lack of pigmentation in the eye

- Ornithine transcarbamylase deficiency; developmental delay and mental retardation. Progressive liver damage, skin lesions, and brittle hair may also be seen

- Siderius X-linked mental retardation syndrome; cleft lip and palate with mental retardation and facial dysmorphism, caused by mutations in the histone demethylase PHF8

- Simpson-Golabi-Behmel syndrome; coarse faces with protruding jaw and tongue, widened nasal bridge, and upturned nasal tip

- Spinal muscular atrophy caused by UBE1 gene mutation; weakness due to loss of the motor neurons of the spinal cord and brainstem

- Wiskott-Aldrich syndrome; eczema, thrombocytopenia, immune deficiency, and bloody diarrhea

- X-linked Severe Combined Immunodeficiency (SCID); infections, usually causing death in the first years of life

- X-linked sideroblastic anemia; skin paleness, fatigue, dizziness and enlarged spleen and liver.

Being an extremely rare autosomal genetic disorder, differential diagnosis has only led to several cases since 1972. Initial diagnosis lends itself to facial abnormalities including sloping forehead, maxillary hypoplasia, nasal bridge depression, wide mouth, dental maloclusion, and receding chin. Electroencephalography (EEG), computed tomography (CT) scanning, and skeletal survey are further required for confident diagnosis. Commonly, diffuse cartilage calcification and brachytelephalangism are identified by X-radiation (X-ray), while peripheral pulmonary arterial stenosis, hearing loss, dysmorphic facies, and mental retardation are confirmed with confidence by the aforementioned diagnostic techniques.

Neonatal-onset multisystem inflammatory disease (abbreviated NOMID, also known as chronic infantile neurologic cutaneous and articular syndrome, or CINCA) is a rare genetic periodic fever syndrome which causes uncontrolled inflammation in multiple parts of the body starting in the newborn period. Symptoms include skin rashes, severe arthritis, and chronic meningitis leading to neurologic damage. It is one of the cryopyrin-associated periodic syndromes.

NOMID can result from a mutation in the "CIAS1" gene (also known as "NLRP3" gene), which helps control inflammation. Mutations in this gene also cause familial cold urticaria and Muckle–Wells syndrome. NOMID has been successfully treated with the drug anakinra.

This syndrome is also known as the Prieur–Griscelli syndrome as it was first described by these authors in 1981.

Primrose syndrome is a rare, slowly progressive genetic disorder that can vary symptomatically between individual cases, but is generally characterised by ossification of the external ears, learning difficulties, and facial abnormalities. It was first described in 1982 in Scotland's Royal National Larbert Institution by Dr D.A.A. Primrose.

Primrose syndrome appears to occur spontaneously, regardless of family history. The cause is currently unknown and there are no known treatments.

MPS-III A, B, C and D are considered to be clinically indistinguishable, although mutations in different genes are responsible for each disease. The following discussion is therefore applicable to all four conditions.

The disease manifests in young children. Affected infants are apparently normal, although some mild facial dysmorphism may be noticeable. The stiff joints, hirsuteness and coarse hair typical of other mucopolysaccharidoses are usually not present until late in the disease. After an initial symptom-free interval, patients usually present with a slowing of development and/or behavioral problems, followed by progressive intellectual decline resulting in severe dementia and progressive motor disease. Acquisition of speech is often slow and incomplete. The disease progresses to increasing behavioural disturbance including temper tantrums, hyperactivity, destructiveness, aggressive behaviour, pica and sleep disturbance. As affected children have normal muscle strength and mobility, the behavioural disturbances are very difficult to manage. The disordered sleep in particular presents a significant problem to care providers. In the final phase of the illness, children become increasingly immobile and unresponsive, often require wheelchairs, and develop swallowing difficulties and seizures. The life-span of an affected child does not usually extend beyond late teens to early twenties.

Although the clinical features of the disease are mainly neurological, patients may also develop diarrhea, carious teeth, and an enlarged liver and spleen. There is a broad range of clinical severity. The disease may very rarely present later in life as a psychotic episode.

Of all the MPS diseases, MPS III produces the mildest physical abnormalities. It is important, however, that simple and treatable conditions such as ear infections and toothaches not be overlooked because of behavior problems that make examination difficult. Children with MPS III often have an increased tolerance of pain. Bumps and bruises or ear infections that would be painful for other children often go unnoticed in children with MPS III. Parents may need to search for a doctor with the patience and interest in treating a child with a long-term illness. Some children with MPS III may have a blood-clotting problem during and after surgery.

The diagnosis may be confirmed by assay of enzyme levels in tissue samples and gene sequencing. Prenatal diagnosis is possible.

Diagnosis is often confirmed by several abnormalities of skeletal origin. There is a sequential order of findings, according to Cormode et al., which initiate in abnormal cartilage calcification and later brachytelephalangism. The uniqueness of brachytelephalangy in KS results in distinctively broadened and shortened first through fourth distal phalanges, while the fifth distal phalanx bone remains unaffected. Radiography also reveals several skeletal anomalies including facial hypoplasia resulting in underdevelopment of the nasal bridge with noticeably diminished alae nasi. In addition to distinguishable facial features, patients generally demonstrate shorter than average stature and general mild developmental delay.

Wolfram syndrome, also called DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), is a rare autosomal-recessive genetic disorder that causes childhood-onset diabetes mellitus, optic atrophy, and deafness as well as various other possible disorders.

It was first described in four siblings in 1938 by Dr. Don J. Wolfram, M.D. The disease affects the central nervous system (especially the brainstem).

The symptoms of Leigh syndrome are classically described as beginning in infancy and leading to death within a span of several years; however, as more cases are recognized, it is apparent that symptoms can emerge at any age—including adolescence or adulthood—and patients can survive for many years following diagnosis. Symptoms are often first seen after a triggering event that taxes the body's energy production, such as an infection or surgery. The general course of Leigh syndrome is one of episodic developmental regression during times of metabolic stress. Some patients have long periods without disease progression while others develop progressive decline.

Infants with the syndrome have symptoms that include diarrhea, vomiting, and dysphagia (trouble swallowing or sucking), leading to a failure to thrive. Children with early Leigh disease also may appear irritable and cry much more than usual. Seizures are often seen. Excess lactate may be seen in the urine, cerebrospinal fluid, and blood of a person with Leigh syndrome.

As the disease progresses, the muscular system is debilitated throughout the body, as the brain cannot control the contraction of muscles. Hypotonia (low muscle tone and strength), dystonia (involuntary, sustained muscle contraction), and ataxia (lack of control over movement) are often seen in people with Leigh disease. The eyes are particularly affected; the muscles that control the eyes become weak, paralyzed, or uncontrollable in conditions called ophthalmoparesis (weakness or paralysis) and nystagmus (involuntary eye movements). Slow saccades are also sometimes seen. The heart and lungs can also fail as a result of Leigh disease. Hypertrophic cardiomyopathy (thickening of part of the heart muscle) is also sometimes found and can cause death; asymmetric septal hypertrophy has also been associated with Leigh syndrome. In children with Leigh-syndrome associated ventricular septal defects, caused by pyruvate dehydrogenase deficiency, high forehead and large ears are seen; facial abnormalities are not typical of Leigh syndrome.

However, respiratory failure is the most common cause of death in people with Leigh syndrome. Other neurological symptoms include peripheral neuropathy, loss of sensation in extremities caused by damage to the peripheral nervous system.

Hypertrichosis is seen in Leigh syndrome caused by mutations in the nuclear gene SURF1.

Leigh syndrome (also called Leigh disease and subacute necrotizing encephalomyelopathy) is an under-recognized inherited neurometabolic disorder that affects the central nervous system. It is named after Archibald Denis Leigh, a British neuropsychiatrist who first described the condition in 1951.

An individual displaying MERRFs syndrome will manifest not only a single symptom, but regularly patients display more than one affected body part at a time. It has been observed that patients with MERRF syndrome will primarily display Myoclonus as a first symptom, along with it they can also manifest seizures, cerebellar ataxia and myopathy. Secondary features include dementia, optic atrophy, bilateral deafness, peripheral neuropathy, spasticity or multiple lipomata. Additional symptoms include dementia, optic atrophy, bilateral deafness and peripheral neuropathy, spasticity, lipomatosis, and/or cardiomyopathy with wolff parkinson-white syndrome. Most patients will not exhibit all of these symptoms, however more than one of these symptoms will be present in a patient who has been diagnosed with MERRFS disease. Due to the multi-symptoms presented by the individual, the severity of the syndrome is very difficult to evaluate. Mitochondrial disorders may present at any age, and this holds truth for MERRS, since it forms part of them. Therefore, if a patient is presenting some of these symptoms, the doctor is able to narrow it down to MEERF mitochondrial disorder.