The prognosis is poor; affected individuals are either stillborn or die shortly after birth. The longest survival reported in literature is of 134 days.

This syndrome is transmitted as an autosomal recessive disorder and there is a risk for recurrence of 25% in future pregnancies.

Children with Pfeiffer syndrome types 2 and 3 "have a higher risk for neurodevelopmental disorders and a reduced life expectancy" than children with Pfeiffer syndrome type 1, but if treated, favorable outcomes are possible. In severe cases, respiratory and neurological complications often lead to early death.

The cause of Goldenhar syndrome is largely unknown. However, it is thought to be multifactorial, although there may be a genetic component, which would account for certain familial patterns. It has been suggested that there is a branchial arch development issue late in the first trimester.

An increase in Goldenhar syndrome in the children of Gulf War veterans has been suggested, but the difference was shown to be statistically insignificant.

The true prevalence of PMS has not been determined. More than 1200 people have been identified worldwide according the Phelan-McDermid Syndrome Foundation. However, it is believed to be underdiagnosed due to inadequate genetic testing and lack of specific clinical features. It is known to occur with equal frequency in males and females. Studies using chromosomal microarray for diagnosis indicate that at least 0.5% of cases of ASD can be explained by mutations or deletions in the "SHANK3" gene. In addition when ASD is associated with ID, "SHANK3" mutations or deletions have been found in up to 2% of individuals.

Autoimmune polyendocrine syndrome type 2, a form of autoimmune polyendocrine syndrome also known as Schmidt's syndrome, or APS-II, is the most common form of the polyglandular failure syndromes. It is heterogeneous and has not been linked to one gene. Rather, individuals are at a higher risk when they carry a particular human leukocyte antigen (HLA-DQ2, HLA-DQ8 and HLA-DR4). APS-II affects women to a greater degree than men.

Prevalence ranges from 1 in 3500 to 5600 live births. Male-female ratio is found to be 3:2.

Recent findings in genetic research have suggested that a large number of genetic disorders, both genetic syndromes and genetic diseases, that were not previously identified in the medical literature as related, may be, in fact, highly related in the genetypical root cause of the widely varying, phenotypically-observed disorders. Thus, Alstrom syndrome is a ciliopathy. Other known ciliopathies include primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Meckel-Gruber syndrome and some forms of retinal degeneration.

Perlman syndrome is a rare disease with an estimated incidence of less than 1 in 1,000,000. As of 2008, less than 30 patients had ever been reported in the world literature.

A prognosis for Alström syndrome is complicated because it widely varies. Any person that has the syndrome have different set of disorders. Permanent blindness, deafness, and Type 2 diabetes may occur. Liver and kidney failure can progressively get worse. The life expectancy is usually reduced and the patients rarely live past 50 years old.

Symptoms(and signs) that are consistent with this disorder are the following:

With appropriate treatment and management, patients with Weaver syndrome appear to do well, both physically and intellectually, throughout their life and have a normal lifespan. Their adult height is normal as well.

The incidence of Fraser syndrome is 0.043 per 10,000 live born infants and 1.1 in 10,000 stillbirths, making it a rare syndrome.

NBCCS has an incidence of 1 in 50,000 to 150,000 with higher incidence in Australia. One aspect of NBCCS is that basal-cell carcinomas will occur on areas of the body which are not generally exposed to sunlight, such as the palms and soles of the feet and lesions may develop at the base of palmar and plantar pits.

One of the prime features of NBCCS is development of multiple BCCs at an early age, often in the teen years. Each person who has this syndrome is affected to a different degree, some having many more characteristics of the condition than others.

Weaver syndrome and Sotos syndrome are often mistaken for one another due to their significant phenotypic overlap and similarities. Clinical features shared by both syndromes include overgrowth in early development, advanced bone age, developmental delay, and prominent macrocephaly. Mutations in the NSD1 gene may also be another cause for confusion. The NSD1 gene provides instructions for making a protein that is involved in normal growth and development. Deletions and mutations in the NSD1 gene is a common cause for patients with Sotos syndrome and in some cases for Weaver syndrome as well.

Features distinguishing Weaver syndrome from Sotos syndrome include broad forehead and face, ocular hypertelorism, prominent wide philtrum, micrognathia, deep-set nails, retrognathia with a prominent chin crease, increased prenatal growth, and a carpal bone age that is greatly advanced compared to metacarpal and phalangeal bone age.

The fifth type of hyper-IgM syndrome has been characterized in three patients from France and Japan. The symptoms are similar to hyper IgM syndrome type 2, but the AICDA gene is intact. These three patients instead had mutations in the catalytic domain of uracil-DNA glycosylase, an enzyme that removes uracil from DNA. In both type 2 and type 5 hyper-IgM syndromes, the patients are profoundly deficient in IgG and IgA because the B cells can't carry out the recombination steps necessary to class-switch.

Neu-Laxova syndrome is a heterogeneous metabolic disorder caused by homozygous or compound heterozygous mutations in the "PHGDH", "PSAT1" and "PSPH" genes. These genes are involved in the serine biosynthesis pathway and are essential for cell proliferation.

Mutations in all three genes had been previously identified as the cause of serine-deficiency syndromes. Although there is some clinical overlap between NLS and these neurometabolic disorders, the phenotype in other serine-deficiency disorders is milder.

Acrocallosal syndrome (also known as ACLS) is a rare autosomal recessive syndrome characterized by corpus callosum agenesis, polydactyly, multiple dysmorphic features, motor and mental retardation, and other symptoms. The syndrome was first described by Albert Schinzel in 1979.

It is associated with "GLI3".

Griscelli syndrome type 2 (also known as "partial albinism with immunodeficiency") is a rare autosomal recessive syndrome characterized by variable pigmentary dilution, hair with silvery metallic sheen, frequent pyogenic infections, neutropenia, and thrombocytopenia.

The key problem is the early fusion of the skull, which can be corrected by a series of surgical procedures, often within the first three months after birth. Later surgeries are necessary to correct respiratory and facial deformities.

Qazi–Markouizos syndrome is a rare hereditary condition characterized by non-progressive, congenital hypotonia, severe intellectual disability, an increased proportion of type 2 muscle fibers, which additionally exhibited increased size, as well as dysharmonic skeletal maturation. To date, the molecular mechanism of Qazi–Markouizos syndrome, which is also known as Puerto Rican infant hypotonia syndrome, remains unknown.

Genetic

- Inborn errors of metabolism

1. Congenital disorder of glycosylation

2. Mitochondrial disorders

3. Peroxisomal disorder

4. Glucose transporter defect

5. Menkes disease

6. Congenital disorders of amino acid metabolism

7. Organic acidemia

Syndromes

- Contiguous gene deletion

1. 17p13.3 deletion (Miller–Dieker syndrome)

- Single gene defects

1. Rett syndrome (primarily girls)

2. Nijmegen breakage syndrome

3. X-linked lissencephaly with abnormal genitalia

4. Aicardi–Goutières syndrome

5. Ataxia telangiectasia

6. Cohen syndrome

7. Cockayne syndrome

Acquired

- Disruptive injuries

1. Traumatic brain injury

2. Hypoxic-ischemic encephalopathy

3. Ischemic stroke

4. Hemorrhagic stroke

- Infections

1. Congenital HIV encephalopathy

2. Meningitis

3. Encephalitis

- Toxins

1. Lead poisoning

2. Chronic renal failure

- Deprivation

1. Hypothyroidism

2. Anemia

3. Congenital heart disease

4. Malnutrition

Genetic factors may play a role in causing some cases of microcephaly. Relationships have been found between autism, duplications of chromosomes, and macrocephaly on one side. On the other side, a relationship has been found between schizophrenia, deletions of chromosomes, and microcephaly. Moreover, an association has been established between common genetic variants within known microcephaly genes ("MCPH1, CDK5RAP2") and normal variation in brain structure as measured with magnetic resonance imaging (MRI)i.e., primarily brain cortical surface area and total brain volume.

The spread of Aedes mosquito-borne Zika virus has been implicated in increasing levels of congenital microcephaly by the International Society for Infectious Diseases and the US Centers for Disease Control and Prevention. Zika can spread from a pregnant woman to her fetus. This can result in other severe brain malformations and birth defects. A study published in The New England Journal of Medicine has documented a case in which they found evidence of the Zika virus in the brain of a fetus that displayed the morphology of microcephaly.

RHBDF2 may also play a role in ovarian epithelial cancer.

Possible associations with gastric cancer and lung cancer have been suggested. Other possible associations include corneal defects, congenital pulmonary stenosis, total anomalous pulmonary venous connection deafness and optic atrophy.

Acrocallosal syndrome (ACLS, ACS, Schinzel-Type) is a rare, heterogeneous, autosomal recessive disorder [3]. The heterogeneity of this condition refers to the multiple genes that may function to contribute to varying degrees of this syndrome [3] and is often linked to consanguinity [2,5]. Characteristics of this syndrome include agenesis of the corpus, macrocephaly, hypertelorism, polydactyly, mental and motor retardation [2], craniofacial dysmorphism, hallux dudplication [3], and sometimes palatal clefting [5]. It has also been reported that there are many similar signs and symptoms between ACLS, Greig cephalopolysyndactyly, and Hydrolethalus Syndrome (HLS), although there is little evidence to support common genetic causation at this point [3].

This condition is inherited as an autosomal dominant syndrome and characterized by palmoplantar keratoderma, oral precursor lesions particularly on the gums (leukoplakia) and a high lifetime risk of esophageal cancer (95% develop esophageal cancer by the age of 65). Relapsing cutaneous horns of the lips has been reported in this condition.

There are several types of this condition have been described – epidermolytic (Vörner type) and non-epidermolytic. Another classification divides these into an early onset type (type B) which occurs in the first year of life and is usually benign and a type A tylosis which occurs between the ages of 5 and 15 years and is strongly associated with esophageal cancer.

Cytoglobin gene expression in oesphageal biopsies is significantly reduced (70% reduction) in this condition. The mechanism of this change is not known.

The minimal deletion causing this syndrome has been defined as a 3 megabase region that contains the genes GPR35, GPC1 and STK25.

Almost all deletions are found to be terminal deletions at the end of chromosome 2. There is a high frequency of "de novo" deletions, but multiple cases within a single family are also observed. Equal proportions of maternally and paternally derived rearrangements were seen in Aldred's series. No common breakpoints for the deletion were identified indicating that the 2q37 rearrangement is unlikely to be mediated by non-homologous recombination and low-copy repeats. In a study of 20 patients, no clear relationship was found between clinical features and the size or position of the monosomic region.