Familial dysautonomia is seen almost exclusively in Ashkenazi Jews and is inherited in an autosomal recessive fashion. Both parents must be carriers in order for a child to be affected. The carrier frequency in Jewish individuals of Eastern European (Ashkenazi) ancestry is about 1/30, while the carrier frequency in non-Jewish individuals is unknown. If both parents are carriers, there is a one in four, or 25%, chance with each pregnancy for an affected child. Genetic counseling and genetic testing is recommended for families who may be carriers of familial dysautonomia.

Worldwide, there have been approximately 600 diagnoses recorded since discovery of the disease, with approximately 350 of them still living.

In affected individuals presenting with the ICCA syndrome, the human genome was screened with microsatellite markers regularly spaced, and strong evidence of linkage with the disease was obtained in the pericentromeric region of chromosome 16, with a maximum lod score, for D16S3133 of 6.76 at a recombination fraction of 0. The disease gene has been mapped at chromosome 16p12-q12.This linkage has been confirmed by different authors. The chromosome 16 ICCA locus shows complicated genomic architecture and the ICCA gene remains unknown.

In January 2001, researchers at Fordham University and Massachusetts General Hospital simultaneously reported finding the genetic mutation that causes FD, a discovery that opens the door to many diagnostic and treatment possibilities.

Despite that it probably would not happen in the near future, some expect that stem-cell therapy will result. Eventually, treatment could be given in utero.

While that may be years ahead, genetic screening became available around April 2001, enabling Ashkenazi Jews to find out if they are carriers. Screening organization Dor Yeshorim offers to test as part of its panel, which also includes Tay-Sachs disease and cystic fibrosis.

In the meantime, more research into treatments is being funded by the foundations that exist. These foundations are organized and run by parents of those with FD. There is no governmental support beyond recognizing those diagnosed with FD as eligible for certain programs.

Infantile convulsions and choreoathetosis (ICCA) syndrome is a neurological genetic disorder with an autosomal dominant mode of inheritance. It is characterized by the association of benign familial infantile epilepsy (BIFE) at age 3–12 months and later in life with paroxysmal kinesigenic choreoathetosis. The ICCA syndrome was first reported in 1997 in four French families from north-western France and provided the first genetic evidence for common mechanisms shared by benign infantile seizures and paroxysmal dyskinesia. The epileptic origin of PKC has long been a matter of debates and PD have been classified as reflex epilepsies.Indeed, attacks of PKC and epileptic seizures have several characteristics in common, they both are paroxysmal in presentation with a tendency to spontaneous remission, and a subset of PKC responds well to anticonvulsants. This genetic disease has been mapped to chromosome 16p-q12. More than 30 families with the clinical characteristics of ICCA syndrome have been described worldwide so far.

May–White syndrome is a rare familial progressive myoclonus epilepsy with lipomas, deafness, and ataxia. This syndrome is probably a familial form of mitochondrial encephalomyopathy.

Benign familial infantile epilepsy (BFIE), also known as benign familial infantile seizures (BFIS) or benign familial infantile convulsions (BFIC) is an epilepsy syndrome. Affected children, who have no other health or developmental problems, develop seizures during infancy. These seizures have focal origin within the brain but may then spread to become generalised seizures. The seizures may occur several times a day, often grouped in clusters over one to three days followed by a gap of one to three months. Treatment with anticonvulsant drugs is not necessary but they are often prescribed and are effective at controlling the seizures. This form of epilepsy resolves after one or two years, and appears to be completely benign. The EEG of these children, between seizures, is normal. The brain appears normal on MRI scan.

A family history of epilepsy in infancy distinguishes this syndrome from the non-familial classification (see benign infantile epilepsy), though the latter may be simply sporadic cases of the same genetic mutations. The condition is inherited with an autosomal dominant transmission. There are several genes responsible for this syndrome, on chromosomes 2, 16 and 19. It is generally described as idiopathic, meaning that no other neurological condition is associated with it or causes it. However, there are some forms that are linked to neurological conditions. One variant known as infantile convulsions and choreoathetosis (ICCA) forms an association between BFIE and paroxysmal kinesigenic choreoathetosis and has been linked to the PRRT2 gene on chromosome 16. An association with some forms of familial hemiplegic migraine (FHM) has also been found. Benign familial infantile epilepsy is not genetically related to benign familial neonatal epilepsy (BFNE), which occurs in neonates. However, a variation with seizure onset between two days and seven months called "benign familial neonatal–infantile seizures" (BFNIS) has been described, which is due to a mutation in the SCN2A gene.

Carnitine palmitoyltransferase II deficiency, Conn's syndrome, Adrenal insufficiency, Hyperthyroidism, Hypothyroidism, Diabetes, Hypogonadism, postorgasmic illness syndrome (POIS).

The most common causes of myalgia by injury are: sprains and strains.

The cause of this condition is unknown but evidence of familial inheritance and sporadic genetic mutation has been linked to cases of FHS. Two possibly familial cases have been reported—one in a mother and son, and the other in a mother and daughter. This suggests an autosomal dominant inheritance but additional cases need to be investigated to establish this. Another report has suggested that the inheritance may be autosomal recessive. In all of these cases, however, the mothers and children were not similarly affected, suggesting a variable clinical expression of the syndrome.

In a study published by the "American Journal of Human Genetics" in 2012, exome sequencing was used to investigate a group of unrelated individuals with classic features of FHS and identified heterozygous mutations in SRCAP as causative of this disorder. Each reported mutation was truncating (nonsense or frameshift) and occurred between codons 2,407 and 2,517 in exon 34, resulting in the loss of three C-terminal AT-hook motifs. SRCAP encodes a SNF2-related chromatin-remodeling ATPase that is a coactivator for CREB-binding protein (or CBP), which is the major cause of Rubinstein–Taybi syndrome. This disrupted interaction between the proteins most likely explains the clinical overlap between FHS and RTS.

- SRCAP has been shown to transduce signals of nuclear (steroid) hormone receptors and Notch pathways, showing that it plays diverse roles in gene expression.

- SRCAP contains several functional domains (SNF2 like ATPase, an N-terminal HSA domain, and three C-terminal AT-hook DNA-binding motifs).

- The CBP interaction domain of SRCAP is located centrally.

Thus, the mechanism of disease in FHS is suspected to be dominant-negative (or antimorphic) due to the mutation in the final exon that results in the loss of the major transactivation function of SRCAP (or loss of one or more critical domains). All of the patients that carried the mutation also had obvious physical symptoms (i.e., prominent nose, delayed bone age, and short stature). Those who tested negative for the mutation often had dysmorphic facial features distinct from classical FHS, as well as a formal diagnosis of autism.

Floating–Harbor syndrome, also known as Pelletier–Leisti syndrome, is a rare disease with fewer than 50 cases described in the literature. It is usually diagnosed in early childhood and is characterized by the triad of proportionate short stature with delayed bone age, characteristic facial appearance, and delayed speech development. Although its cause is unknown, it is thought to result from genetic mutation, and diagnosis is established by the presence of a heterozygous SRCAP mutation in those with clinical findings of FHS.

Overall, the prognosis for patients with NOMID is not good, though many (80%) live into adulthood, and a few appear to do relatively well. They are at risk for leukemia, infections, and some develop deposits of protein aggregated called amyloid, which can lead to kidney failure and other problems. The neurologic problems are most troubling. The finding that other diseases are related and a better understanding of where the disease comes from may lead to more effective treatments.

Familial British dementia is a form of dementia. It was first reported by Cecil Charles Worster-Drought in 1933 and is therefore also known as Worster-Drought syndrome. It is caused by a mutation in the ITM2B gene (also known as BRI2); a different mutation of the same gene causes the similar syndrome of familial Danish dementia. The combination of amyloid pathology and neurofibrillary tangles has led to comparison with the pathology of Alzheimer's disease.

NPCA is a syndrome and can have diverse causes. It has a genetic basis and inheritance is considered to be autosomal recessive. However, autosomal dominant variety has also been reported. There may be familial balanced translocation t(8;20)(p22;q13) involved.

This is a rare condition with an incidence estimated to be less than 1 in a million live births. About 100 cases have been reported worldwide. The bulk of cases are sporadic but familial forms with autosomal dominant transmission have also been described.

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

A team from the National Institute of Nutrition, Hyderabad conducted research in the affected regions and found out that the disease was confined to a dalit colony. They also found out that the disease was affecting people of all age groups and it was non-contagious and non-infectious. This research was further followed by research conducted over four years (1984–88) by the Indian Council of Medical Research (ICMR). Study groups involving experts from different medical fields were formed and these groups visited the affected places to conduct experiments. They were also helped by the Health Department of Karnataka who also provided a team to assist them. Despite undertaking extensive research, the team could not come into any conclusion on the cause of the disease. The team wound up in 1988 and this was the first phase of their research. The second phase of the research by ICMR was started in the year 2001 under the leadership of S. S. Agarwal of the Sanjay Gandhi Post-graduate centre in Lucknow. Some of the activities in the second phase were to x-ray the patients and also study their family history to see if the disease was related to genetics. The study reported that Handigodu syndrome is a syndrome of familial spondyloepi(meta)physeal dysplasia. It is inherited as an autosomal dominant trait. All the presentations of the varied manifestation of the disease could be explained as being caused by defective development of bones as a result of monogenic disorder.

Symptoms of the disease are an acute pain and swelling in the hips and knee joints. Some of the other characteristics of this disease are dwarfism from birth, deformation of the limbs after age seven and death as early as between 25 and 30 years or even younger. Depending on the mobility of the affected patients, the disease has been identified with three severities: in mild to moderate cases, the patient is able to walk with difficulty, in severe cases mobility is very restricted, whereas in acute cases the limbs are bent and badly crippled making the patients crawl.

Benign hereditary chorea (BHC), also known as benign familial chorea, is a rare autosomal dominant neurogenetic syndrome. It typically presents in childhood with isolated chorea. Unlike other neurogenetic causes of chorea such as Huntington's disease, BHC is not progressive, and not associated with cognitive decline or psychiatric problems in the vast majority of cases.

BHC is caused by a single-nucleotide insertion mutation in "TITF1", which encodes thyroid transcription factor 1 (TTF-1). This gene is also known as NK2 homeobox 1 (NKX2-1)

In some cases, additional developmental abnormalities of lung and thyroid tissue are found in BHC, leading to the suggested alternative name "brain-lung-thyroid syndrome".

It is not known how mevalonate kinase mutations cause the febrile episodes, although it is presumed that other products of the cholesterol biosynthesis pathyway, the prenylation chains (geranylgeraniol and farnesol) might play a role.

The cause of the disease is unknown. It was originally thought that the epidermal changes were secondary to profound malnutrition as a result of protein-losing enteropathy. Recent findings have called this hypothesis into question; specifically, the hair and nail changes may not improve with improved nutrition.

Other conditions consisting of multiple hamartomatous polyps of the digestive tract include Peutz-Jeghers syndrome, juvenile polyposis, and Cowden disease. Related polyposis conditions are familial adenomatous polyposis, attenuated familial adenomatous polyposis, Birt–Hogg–Dubé syndrome and MUTYH.

Office of Rare Diseases listed Lyngstadaas syndrome as a "rare disease". This means that Lyngstadaas syndrome, or a subtype of Lyngstadaas syndrome, affects less than 200,000 people in the US population.

Orphanet, a consortium of European partners, currently defines a condition rare when if affects 1 person per 2,000. They list Lyngstadaas syndrome as a "rare disease".

Hyperimmunoglobulinemia D with recurrent fever (HIDS) is a periodic fever syndrome originally described in 1984 by the internist Jos van der Meer, then at Leiden University Medical Centre. No more than 300 cases have been described worldwide.

The syndromes within CAPS overlap clinically, and patients may have features of more than one disorder. In a retrospective cohort of 136 CAPS patients from 16 countries, the most prevalent clinical features were fever (84% of cases, often with concurrent constitutional symptoms such as fatigue, malaise, mood disorders or failure to thrive), skin rash (either urticarial or maculopapular rash; 97% of cases) especially after cold exposure, and musculoskeletal involvement (myalgia, arthralgia, and/or arthritis, or less commonly joint contracture, patellar overgrowth, bone deformity, bone erosion and/or osteolytic lesion; 86% of cases). Less common features included ophthalmological involvement (conjunctivitis and/or uveitis, or less commonly optic nerve atrophy, cataract, glaucoma or impaired vision; 71% of cases), neurosensory hearing loss (42% of cases), neurological involvement (morning headache, papilloedema, and/or meningitis, or less commonly seizure, hydrocephalus or mental retardation; 40% of cases), and AA amyloidosis (4% of cases). Age of onset is typically in infancy or early childhood. In 57% of cases, CAPS had a chronic phenotype with symptoms present almost daily, whereas the remaining 43% of patients experienced only acute episodes. Up to 56% of patients reported a family history of CAPS. Previous studies confirm these symptoms, although the exact reported rates vary.

Cryopyrin-associated periodic syndrome (CAPS) is a group of rare, heterogeneous autoinflammatory disease characterized by interleukin 1β-mediated systemic inflammation and clinical symptoms involving skin, joints, central nervous system, and eyes. It encompasses a spectrum of three clinically overlapping autoinflammatory syndromes including familial cold autoinflammatory syndrome (FCAS, formerly termed familial cold-induced urticaria), the Muckle–Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disease (NOMID, also called chronic infantile neurologic cutaneous and articular syndrome or CINCA) that were originally thought to be distinct entities, but in fact share a single genetic mutation and pathogenic pathway.

Hereditary gelsolin amyloidosis is a cutaneous condition inherited in an autosomal dominant fashion.

The condition was first described in 1969, by the Finnish ophthalmologist Jouko Meretoja, and is also known as Familial amyloid neuropathy type IV, Meretoja syndrome, Hereditary amyloidosis, Finnish type.

The disorder primarily associated with eye, skin and cranial nerve symptoms. It is a form of amyloidosis, where the amyloid complexes are formed from fragments of the protein gelsolin in the plasma, due to a mutation in the GSN gene (c.654G>A or c.654G>T).