CCD causes persistent secretory diarrhea. In a fetus, it leads to polyhydramnios and premature birth. Immediately after birth, it leads to dehydration, hypoelectrolytemia, hyperbilirubinemia, abdominal distention, and failure to thrive.

Like other mitochrondrial diseases, "MNGIE is a multisystem disorder". MNGIE primarily affects the gastrointestinal and neurological systems. Gastrointestinal symptoms may include gastrointestinal dysmotility, due to inefficient peristalsis, which may result in pseudo-obstruction and cause malabsorption of nutrients. Additionally, gastrointestinal symptoms such as borborygmi, early satiety, diarrhea, constipation, gastroparesis, nausea, vomiting, weight loss, and diverticulitis may be present in MNGIE patients. Neurological symptoms may include diffuse leukoencephalopathy, peripheral neuropathy, and myopathy. Ocular symptoms may include retinal degeneration, ophthalmoplegia, and ptosis. Those with MNGIE are often thin and experience continuous weight loss. The characteristic thinness of MNGIE patients is caused by multiple factors including inadequate caloric intake due to gastrointestinal symptoms and discomfort, malabsorption of food from bacterial overgrowth due to decreased motility, as well as an increased metabolic demand due to inefficient production of ATP by the mitochondria.

Not all of the DOOR symptoms are consistently present. They can vary in severity, and additional features can be noted in individuals affected by DOOR syndrome.

Some of these additional features are:

- Polyhydramnios (increased amniotic fluid during pregnancy) and increased nuchal fold during pregnancy

- Specific facial features such as a large nose

- Severe and sometimes refractory seizures, abnormalities on the magnetic resonance imaging of the brain

- Increased 2-oxoglutaric acid in the blood and urine - this compound is made or used by several enzymes

- Finger-like thumbs

- Visual impairment

- Peripheral neuropathy (nerves conducting sensation from extremities to the brain) and insensivity to pain

Intellectual impairment is present in all reported cases, but the severity can vary widely. The prognosis in terms of survival also varies greatly from early childhood till adulthood.

It is a genetic developmental disorder with clinical diversity characterized by hypoparathyroidism, sensorineural deafness and renal disease. Patients usually present with hypocalcaemia, tetany, or afebrile convulsions at any age. Hearing loss is usually bilateral and may range from mild to profound impairment. Renal disease includes nephrotic syndrome, cystic kidney, renal dysplasia, hypoplasia or aplasia, pelvicalyceal deformity, vesicoureteral reflux, chronic kidney disease, hematuria, proteinuria and renal scarring.

Congenital fiber type disproportion (CFTD) is an inherited form of myopathy with small type 1 muscle fibers that may occur in a number of neurological disorders. It has a relatively good outcome and follows a stable course. While the exact genetics is unclear there is an association with TPM3, ACTA1 and SEPN1 gene mutations. It is a rare condition.

BVVL is marked by a number of cranial nerve palsies, including those of the motor components involving the 7th and 9th-12th cranial nerves, spinal motor nerves, and upper motor neurons. Major features of BVVL include facial and neck weakness, fasciculation of the tongue, and neurological disorders from the cranial nerves. The neurological manifestations develop insidiously: they usually begin with sensorineural deafness, progress inexorably to paralysis, and often culminate in respiratory failure. Most mortality in patients has been from either respiratory infections or respiratory muscle paralysis. Pathological descriptions of BVVL include injury and depletion of 3rd-7th cranial nerves, loss of the spinal anterior horn cells, degeneration of Purkinje cells, as well as degeneration of the spinocerebellar and pyramidal tracts. The first symptoms in nearly all cases of BVVL is progressive vision loss and deafness, and the first initial symptoms are seen anywhere from one to three years.

Most cases of deafness are followed by a latent period that can extend anywhere from weeks to years, and this time is usually marked by cranial nerve degeneration. Neurological symptoms of BVVL include optic atrophy, cerebellar ataxia, retinitis pigmentosa, epilepsy and autonomic dysfunction. Non-neurological symptoms can include diabetes, auditory hallucinations, respiratory difficulties, color blindness, and hypertension.

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).

DOOR (deafness, onychdystrophy, osteodystrophy, and mental retardation) syndrome is a genetic disease which is inherited in an autosomal recessive fashion. DOOR syndrome is characterized by mental retardation, sensorineural deafness, abnormal nails and phalanges of the hands and feet, and variable seizures. A similar deafness-onychodystrophy syndrome is transmitted as an autosomal dominant trait and has no mental retardation. Some authors have proposed that it may be the same as Eronen Syndrome, but since both disorders are extremely rare it is hard to make a determination.

The symptoms of CCD are variable, but usually involve hypotonia (decreased muscle tone) at birth, mild delay in child development (highly variable between cases), weakness of the facial muscles, and skeletal malformations such as scoliosis and hip dislocation.

Symptoms may be present at birth or may appear at any stage of life. There appears to be a growing number of people who do not become symptomatic until adulthood to middle age. While generally not progressive, again there appears to be a growing number of people who do experience a slow clinically significant progression of symptomatology. These cases may hypothetically be due to the large number of gene mutations of ryanodine receptor malfunction, and with continued research may in fact be found to be clinical variants.

CCD may be detectable on prenatal ultrasound. After birth, signs in affected babies typically are abdominal distension, visible peristalsis, and watery stools persistent from birth that show chloride loss of more than 90 mmol/l.

An important feature in this diarrhea that helps in the diagnosis, is that it is the only type of diarrhea that causes metabolic alkalosis rather than metabolic acidosis.

Mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE) is a rare autosomal recessive mitochondrial disease. It has been previously referred to as polyneuropathy, ophthalmoplegia, leukoencephalopathy, and POLIP syndrome. The disease presents in childhood, but often goes unnoticed for decades. Unlike typical mitochondrial diseases caused by mitochondrial DNA (mtDNA) mutations, MNGIE is caused by mutations in the TYMP gene, which encodes the enzyme thymidine phosphorylase. Mutations in this gene result in impaired mitochondrial function, leading to intestinal symptoms as well as neuro-ophthalmologic abnormalities. "A secondary form of MNGIE, called MNGIE without leukoencephalopathy, can be caused by mutations in the POLG gene".

Brown-Vialetto-Van-Laere syndrome (BVVL), sometimes known as Brown's Syndrome, is a rare degenerative disorder often initially characterized by progressive sensorineural deafness.

The syndrome most often affects children, adolescents, and young adults. As knowledge of BVVL grows some adult patients have now been diagnosed. There is no known cure, however with prompt treatment the prognosis may be positive with some patients stabilizing and even minor improvements noted in certain cases.

The first symptom is typically diabetes mellitus, which is usually diagnosed around the age of 6. The next symptom to appear is often optic atrophy, the wasting of optic nerves, around the age of 11. The first signs of this are loss of colour vision and peripheral vision. The condition worsens over time, and people with optic atrophy are usually blind within 8 years of the first symptoms. Life expectancy of people suffering from this syndrome is about 30 years.

Michel aplasia, also known as complete labyrinthine aplasia (CLA), is a congenital abnormality of the inner ear. It is characterized by the bilateral absence of differentiated inner ear structures and results in complete deafness (anacusis).

Michel aplasia should not be confused with michel dysplasia. It may affect one or both ears.

"Aplasia" is the medical term for body parts that are absent or do not develop properly. In Michel aplasia, the undeveloped (anaplastic) body part is the bony labyrinth of the inner ear. Other nearby structures may be underdeveloped as well.

Common symptoms of the disease are weakness and atrophy in the distal muscles of the lower limbs which progresses to the hands and arms, then to the trunk, neck and face. Respiratory impairment often follows.

The presentation of mitochondrial trifunctional protein deficiency may begin during infancy, features that occur are: low blood sugar, weak muscle tone, and liver problems. Infants with this disorder are at risk for heart problems, breathing difficulties, and pigmentary retinopathy. Signs and symptoms of mitochondrial trifunctional protein deficiency that may begin "after" infancy include hypotonia, muscle pain, a breakdown of muscle tissue, and a loss of sensation in the extremities called peripheral neuropathy. Some who have MTP deficiency show a progressive course associated with myopathy, and recurrent rhabdomyolysis.

Abnormal development of the skeletal portions of the second arch

1. Nondifferentiation of the stapes, with resultant absence of round and oval window.

2. Abnormal course of the facial nerve.

Skull base abnormalities

1. Hypoplasia of the petrous temporal bone.

2. Hypoplastic and sclerotic petrous apex may mimic labyrinthitis ossificans.

3. Platybasia.

4. Aberrant course of jugular veins.

Central core disease (CCD), also known as central core myopathy, is an autosomal dominant congenital myopathy (inborn muscle disorder). It was first described by Shy and Magee in 1956. It is characterized by the appearance of the myofibril under the microscope.

Barakat syndrome, is a rare disease characterized by hypoparathyroidism, sensorineural deafness and renal disease, and hence also known as HDR syndrome. It was first described by Amin J. Barakat et al. in 1977.

Desmin-related myofibrillar myopathy is a subgroup of the myofibrillar myopathy diseases and is the result of a mutation in the gene that codes for desmin which prevents it from forming protein filaments, instead forming aggregates of desmin and other proteins throughout the cell.

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.

Centronuclear myopathies (CNM) are a group of congenital myopathies 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.

Symptoms of CNM include severe hypotonia, hypoxia-requiring breathing assistance, and scaphocephaly. Among centronuclear myopathies, the X-linked myotubular myopathy form typically presents at birth, and is thus considered a congenital myopathy. However, some centronuclear myopathies may present later in life.

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.

Keratitis–ichthyosis–deafness syndrome (also known as "Erythrokeratodermia progressiva Burns," "Ichthyosiform erythroderma, corneal involvement, and deafness," and "KID syndrome,") presents at birth/infancy and is characterized by pregressive corneal opacification, either mild generalized hyperkeratosis or discrete erythematous plaques, and neurosensory deafness.

It is caused by a mutation in connexin 26.

Patients with CED complain of chronic bone pain in the legs or arms, muscle weakness (myopathy) and experience a waddling gait. Other clinical problems associated with the disease include increased fatigue, weakness, muscle spasms, headache, difficulty gaining weight, and delay in puberty. Some patients have an abnormal or absent tibia, may present with a flat foot, or scoliosis.

This disease may also cause bones to become abnormally hardened which is referred to as sclerosis. This hardening may affect the bones at the base of the skull or those in the hands, feet, or jaw. This causes ongoing pain and aching within the body parts that are affected. The pain has been described as either a hot electric stabbing pain, an ever-increasing pressure sensation around the bones (especially before electrical storms) or as a constant ache that radiates through several long bones at once. Pain may also occur in the hips, wrists, knees and other joints as they essentially just 'lock-up' (often becoming very stiff, immobile and sore), mostly when walking up or down staircases, writing for extended periods of time, or during the colder months of the year. Those with the disease tend to have a very characteristic walk medically diagnosed as a 'waddling gait'. This is observed by the broad-based gait with a duck-like waddle to the swing phase, the pelvis drops to the side of the leg being raised, notable forward curvature of the lumbar spine and a marked body swing.

The pain is especially severe during a 'flare-up', these can be unpredictable, exhausting and last anywhere from a few hours to several weeks. This is a common occurrence for several CED patients, often causing myopathy and extensive sleep deprivation from the chronic, severe and disabling pain. Patients may even require the use of a wheelchair (or additional carer's help with getting dressed, showering, mobility/shopping, preparing meals or lifting heavy items) especially when bedridden or housebound for days or weeks at a time. 'Flare-ups' may be attributed to, or exacerbated by growth spurts, stress, exhaustion, exercise, standing or walking for too long, illness, infection, being accidentally knocked/hurt or injured, after surgery/anaesthetics, cold weather, electrical storms, and sudden changes in barometric pressure.

CED may also affect internal organs, the liver and spleen, which may become enlarged. A loss of vision and/or hearing can occur if bones are adversely affected by the hardening in the skull. Hence proactive specialist check-ups, X-rays, diagnostic tests/scans, and regular blood tests are recommended on an annual basis to monitor the CED bony growth and secondary medical issues that may arise from this condition.