Some specific symptoms vary from one type of leukodystrophy to the next but the vast majority of symptoms are shared as the causes for the disease generally have the same effects. Symptoms are dependent on the age of onset, which is predominantly in infancy and early childhood, although the exact time of onset may be difficult to determine. Hyperirritability and hypersensitivity to the environment are common, as well as some tell-tale physical signs including muscle rigidity and a backwards-bent head. Botox therapy is often used to treat patients with spasticity. Juvenile and adult onsets display similar symptoms including a decrease or loss in hearing and vision. While children do experience optic and auditory degeneration, the course of the disease is usually too rapid, causing death relatively quickly, whereas adults may live with these conditions for many years. In children, spastic activity often precedes progressive ataxia and rapid cognitive deterioration which has been described as mental retardation. Epilepsy is commonplace for patients of all ages. More progressed patients show weakness in deglutition, leading to spastic coughing fits due to inhaled saliva. Classic symptomatic progression of juvenile x-linked adrenoleukodystrophy is shown in the 1992 film, "Lorenzo's Oil".

Course and timetable are dependent on the age of onset with infants showing a lifespan of 2–8 years, juveniles 2–10 years and adults typically 10+ years. Adults typically see an extended period of stability followed by a decline to a vegetative state and death. While treatments do exist, most are in the experimental phase and can only promise a halt in the progression of symptoms, although some gene therapies have shown some symptomatic improvement. The debilitating course of the disease has led to numerous philosophical and ethical arguments over experimental clinical trials, patients’ rights and physician-assisted suicide.

Specific types of leukodystrophies include the following with their respective ICD-10 codes when available:

- (E71.3) Adrenomyeloneuropathy

- (E75.2) Alexander disease

- (E75.5) Cerebrotendineous xanthomatosis

- Hereditary CNS demyelinating disease

- (E75.2) Krabbe disease

- (E75.2) Metachromatic leukodystrophy

- (E75.2) Pelizaeus–Merzbacher disease

- (E75.2) Canavan disease

- (G93.49) Leukoencephalopathy with vanishing white matter

- (E71.3) Adrenoleukodystrophy

- (G60.1) Refsum disease

The Huntington's disease-like syndromes (often abbreviated as HD-like or "HDL" syndromes) are a family of inherited neurodegenerative diseases that closely resemble Huntington's disease (HD) in that they typically produce a combination of chorea, cognitive decline or dementia and behavioural or psychiatric problems.

HDL1 is an unusual, autosomal dominant familial prion disease. Only described in one family, it is caused by an eight-octapeptide repeat insertion in the "PRNP" gene. More broadly, inherited prion diseases in general can mimic HD.

The disease is one in a group of genetic disorders collectively known as leukodystrophies that affect growth of the myelin sheath, the fatty covering—which acts as an insulator—on nerve fibers in the CNS. PMD is generally caused by a recessive mutation of the gene on the long arm of the X-chromosome (Xq21-22) that codes for a myelin protein called proteolipid protein 1 or PLP1.

The onset of Pelizaeus–Merzbacher disease is usually in early infancy. The most characteristic early signs are nystagmus (rapid, involuntary, rhythmic motion of the eyes) and hypotonia (low muscle tone). Motor abilities are delayed or never acquired, mostly depending upon the severity of the mutation. Most children with PMD learn to understand language, and usually have some speech. Other signs may include tremor, lack of coordination, involuntary movements, weakness, unsteady gait, and over time, spasticity in legs and arms. Muscle contractures (shrinkage or shortening of a muscle) often occur over time. Mental functions may deteriorate. Some patients may have convulsions and skeletal deformation, such as scoliosis, resulting from abnormal muscular stress on bones.

There are several forms of Pelizaeus–Merzbacher disease including classic, connatal, transitional, and adult variants. The majority of disease-causing mutations result in duplications of the entire PLP1 gene. Interestingly, deletions at the PLP1 locus (which are rarer) cause a milder form of PMD than is observed with the typical duplication mutations, which demonstrates the critical importance of gene dosage at this locus for normal CNS function. Some of the remaining cases of PMD are accounted for by mutations in the gap junction A12 ("GJA12") gene, and are now called Pelizaeus-Merzbacher-like disease (PMLD). Other cases of apparent PMD do not have mutations in either the "PLP1" or "GJA12" genes, and are presumed to be caused either by mutations in other genes, or by mutations not detected by sequencing the "PLP1" gene exons and neighboring intronic regions of the gene. Among these is a new genetic disorder (discovered in 2003, 2004) which is caused by mutation in the transporter of thyroid hormone, MCT8, also known as SLC16A2, is believed to be account for a significant fraction of the undiagnosed neurological disorders (usually resulting in hypotonic/floppy infants with delayed milestones). This genetic defect was known as Allan–Herndon–Dudley syndrome (since 1944) without knowing its actual cause. Some of the signs for this disorder are as follows: normal to slightly elevated TSH, elevated T and reduced T (ratio of T/T is about double its normal value). Normal looking at birth and for the first few years, hypotonic (floppy), in particular difficulty to hold the head, possibly difficulty to thrive, possibly with delayed myelination (if so, some cases are reported with an MRI pattern similar to Pelizaeus–Merzbacher disease, known as PMD,) possibly with decreased mitochondrial enzyme activities, possibly with fluctuating lactate level. Patients have an alert face, a limited IQ, patients may never talk/walk, 50% need feeding tube, patients have a normal life span. MCT8 can be ruled out with a simple TSH/T/T thyroid test.

Milder mutations of the "PLP1" gene that mainly cause leg weakness and spasticity, with little or no cerebral involvement, are classified as spastic paraplegia 2 (SPG2).

Upington disease, also called Perthes-like hip disease, enchondromata, ecchondromata, and familial dyschondroplasia, is an extremely rare autosomal dominant malformation disorder. It has only one published source claiming its existence in three generations of one family from South Africa.

The diagnosis of PMD is often first suggested after identification by magnetic resonance imaging (MRI) of abnormal white matter (high T2 signal intensity, i.e. T2 lengthening) throughout the brain, which is typically evident by about 1 year of age, but more subtle abnormalities should be evident during infancy. Unless there is a family history consistent with sex-linked inheritance, the condition is often misdiagnosed as cerebral palsy. Once a "PLP1" or "GJA12" mutation is identified, prenatal diagnosis or preimplantation genetic diagnostic testing is possible.

The 'core' neuroacanthocytosis syndromes are chorea acanthocytosis and McLeod syndrome. Acanthocytes are nearly always present in these conditions and they share common clinical features. Some of these features are also seen in the other neurological syndromes associated with neuroacanthocytosis.

A common feature of the core syndromes is chorea: involuntary dance-like movements. In neuroacanthocytosis, this is particularly prominent in the face and mouth which can cause difficulties with speech and eating. These movements are usually abrupt and irregular and present during both rest and sleep.

Individuals with neuroacanthocytosis also often suffer from parkinsonism, the uncontrolled slowness of movements, and dystonia, abnormal body postures. Many affected individuals also have cognitive (intellectual) impairment and psychiatric symptoms such as anxiety, paranoia, depression, obsessive behavior, and pronounced emotional instability. Seizures may also be a symptom of neuroacanthocytosis.

Onset differs between individual neuroacanthocytosis syndromes but is usually between ages 20 and 40. Affected individuals usually live for 10–20 years after onset.

The disease is characterized by Perthes-like pelvic anomalies (premature closure of the capital femoral epiphyses and widened femoral necks with flattened femoral heads), enchondromata and ecchondromata.

The hallmark of the neuroacanthocytosis syndromes is the presence of acanthocytes in peripheral blood. "Acanthocytosis" originated from the Greek word "acantha", meaning thorn. Acanthocytes are spiculated red blood cells and can be caused by altered distribution of membrane lipids or membrane protein/skeleton abnormalities. In neuroacanthocytosis, acanthocytes are caused by protein but not lipid membrane abnormalities

An aging-associated disease is a disease that is most often seen with increasing frequency with increasing senescence. Essentially, aging-associated diseases are complications arising from senescence. Age-associated diseases are to be distinguished from the aging process itself because all adult animals age, save for a few rare exceptions, but not all adult animals experience all age-associated diseases. Aging-associated diseases do not refer to age-specific diseases, such as the childhood diseases chicken pox and measles. "Aging-associated disease" is used here to mean "diseases of the elderly". Nor should aging-associated diseases be confused with accelerated aging diseases, all of which are genetic disorders.

Examples of aging-associated diseases are atherosclerosis and cardiovascular disease, cancer, arthritis, cataracts, osteoporosis, type 2 diabetes, hypertension and Alzheimer's disease. The incidence of all of these diseases increases rapidly with aging (increases exponentially with age, in the case of cancer).

Of the roughly 150,000 people who die each day across the globe, about two thirds—100,000 per day—die of age-related causes. In industrialized nations, the proportion is higher, reaching 90%.

This disease can only be confirmed at the post-mortem, which includes identification of bilaterally symmetrical vacuolation of the neuropil and vacuolation in neurones. Lesions are likely to be found in basal ganglia, cerebral cortex and thalamus of the brain.

Heterogeneous medical condition in medicine are those medical conditions which have several etiologies, like hepatitis or diabetes. Medical conditions are normally defined pathologically (liver inflammation) or clinically (excessive urination) and not etiologically, and therefore it is normal to have more than one cause for them. The word is used as an opposition to homogeneous, meaning that given a group of patients, the disease is the same for all of them.

When a condition is heterogeneous, it is normally divided in endotypes.

Inflammatory demyelinating diseases (IDDs), sometimes called Idiopathic (IIDDs) because the unknown etiology of some of them, and sometimes known as borderline forms of multiple sclerosis, is a collection of multiple sclerosis variants, sometimes considered different diseases, but considered by others to form a spectrum differing only in terms of chronicity, severity, and clinical course.

Multiple Sclerosis for some people is a syndrome more than a single disease. It can be considered among the acquired demyelinating syndromes with a multiphasic instead of monophasic behaviour. Multiple sclerosis also has a prodromal stage in which an unknown underlying condition, able to damage the brain, is present, but no lesion has still developed.

Feline spongiform encephalopathy (FSE) is a prion disease thought to be related or identical to Bovine spongiform encephalopathy (BSE).This disease is known to affect domestic and captive feline species. Lezmi S. et al. (2003), suggested that this infectious agent might be spread by both haematogenous and nervous pathways. Like BSE, this disease can take several years to develop. It is probable, but not proven, that the affected animals contract the disease by eating contaminated bovine meat.

The signs and symptoms of X-linked recessive hypoparathyroidism are characteristic of hypoparathyroidism and its consequent hypocalcemia. They include acute symptoms, like paresthesia, twitching of the hands and feet, unconsciousness, and trouble breathing; and chronic symptoms, including seizures, tiredness, irritability, cardiac insufficiency, abnormal heart rhythms, papilledema, cataracts, calcium deposits in the brain, and loss or brittleness of hair, skin, and nails.

Lichen ruber moniliformis is a rare skin disease named for Fred Wise and Charles R. Rein.

It is one of several diseases also known as Kaposi's disease, based on its characterization in 1886 by Moritz Kaposi.

It is thought to be a rare variety of lichen planus.It is also known as "Morbus moniliformis lichenoides".

By age 3 about 30% of rats have had cancer, whereas by age 85 about 30% of humans have had cancer. Humans, dogs and rabbits get Alzheimer's disease, but rodents do not. Elderly rodents typically die of cancer or kidney disease, but not of cardiovascular disease. In humans, the relative incidence of cancer increases exponentially with age for most cancers, but levels off or may even decline by age 60–75 (although colon/rectal cancer continues to increase).

People with the so-called segmental progerias are vulnerable to different sets of diseases. Those with Werner's syndrome suffer from osteoporosis, cataracts and cardiovascular disease, but not neurodegeneration or Alzheimer's disease; those with Down syndrome suffer type 2 diabetes and Alzheimer's disease, but not high blood pressure, osteoporosis or cataracts. In Bloom syndrome, those afflicted most often die of cancer.

The disease causes numerous whitish punctiform papules and brownish macules arranged in a necklace-like pattern.

Neuroborreliosis is often preceded by the typical symptoms of Lyme disease, which include erythema migrans and flu-like symptoms such as fever and muscle aches. Neurologic symptoms of neuroborreliosis include the meningoradiculitis (which is more common in European patients), cranial nerve abnormalities, and altered mental status. Sensory findings may also be present. Rarely, a progressive form of encephalomyelitis may occur. In children, symptoms of neuroborreliosis include headache, sleep disturbance, and symptoms associated with increased intracranial pressure, such as papilledema, can occur. Less common childhood symptoms can include meningitis, myelitis, ataxia, and chorea. Ocular Lyme disease has also been reported, as has neuroborreliosis affecting the spinal cord, but neither of these findings are common.

An endotype is a subtype of a condition, which is defined by a distinct functional or pathobiological mechanism. This is distinct from a phenotype, which is any observable characteristic or trait of a disease, such as morphology, development, biochemical or physiological properties, or behavior, without any implication of a mechanism. It is envisaged that patients with a specific endotype present themselves within phenotypic clusters of diseases.

One example is asthma, which is considered to be a syndrome, consisting of a series of endotypes. This is related to the concept of disease entity

Some NMO patients present double positive for autoantibodies to AQP4 and MOG. These patients have MS-like brain lesions, multifocal spine lesions and retinal and optic nerves atrophy.

X-linked recessive hypoparathyroidism is a rare, congenital form of hypoparathyroidism.

A number of diseases can produce symptoms similar to those of Lyme neuroborreliosis. They include:

- Alzheimer's disease

- Acute disseminated encephalomyelitis

- Viral meningitis

- Multiple sclerosis

- Bell's palsy

Neuroborreliosis presenting with symptoms consistent with amyotrophic lateral sclerosis has been described.

Diagnosis is determined by clinical examination of visible symptoms. Neuroborreliosis can also be diagnosed serologically to confirm clinical examination via western blot, ELISA, and PCR.

The Baggio–Yoshinari syndrome (BYS), formerly known as the Brazilian Lyme-like disease and Brazilian human borreliosis, is a disease transmitted by the "Amblyomma cajennense" tick, but the organism that causes the infection is still unknown. Clinical features resemble those of Lyme disease (LD).