The recurrence of DOOR in siblings and the finding of DOOR syndrome in a few families with consanguinity suggest that the condition is an autosomal recessive genetic condition. Mutations in TBC1D24 have been identified in 9 families.

This disorder is caused by an abnormality of the TBCE gene, the locus for which is on Chromosome 1q42.3. The locus is a 230 kb region of gene with identified deletions and mutations in affected individuals. There are rare cases of the disorder not being due to a TBCE gene abnormality.

Schimmelpenning syndrome appears to be sporadic rather than inherited, in almost all cases. It is thought to result from genetic mosaicism, possibly an autosomal dominant mutation arising after conception and present only in a subpopulation of cells. The earlier in embryological development such a mutation occurs, the more extensive the nevi are likely to be and the greater the likelihood of other organ system involvement.

First reported from Saudi Arabia in 1988, Sanjad-Sakati syndrome, also known as "Hypoparathyroidism-Retardation-Dysmorphism (HRD) syndrome", or less commonly as the "Middle East syndrome", is a very rare genetically inherited disorder seen in the Middle East and children of Middle Eastern origin elsewhere in the world.The condition is named after Sami A. Sanjad and Nadia Awni Sakati.

Hennekam syndrome also known as intestinal lymphagiectasia–lymphedema–mental retardation syndrome, is an autosomal recessive disorder consisting of intestinal lymphangiectasia, facial anomalies, peripheral lymphedema, and mild to moderate levels of growth and intellectual disability.

It is also known as "lymphedema-lymphangiectasia-mental retardation syndrome".

In a subset of patients it is associated with CCBE1 according research published by its namesake, Raoul Hennekam. Other causal mutations were found in the FAT4 gene. Previously, mutations in the FAT4 gene had been only associated with van Maldergem syndrome. The molecular mechanism of the lymphedema phenotype in CCBE1-associated cases was identified as a diminished ability of the mutated CCBE1 to accelerate and focus the activation of the primary lymphangiogenic growth factor VEGF-C.

Alopecia contractures dwarfism mental retardation syndrome or (ACD mental retardation syndrome) is a developmental disorder which causes mainly baldness and dwarfism in combination with intellectual disability; skeletal anomalies, caries and nearsightedness are also typical.

The ACD mental retardation syndrome was first described in 1980 by Albert Schinzel and only few cases have since been identified in the world. At the time Dr. Schinzel made no conclusion of the hereditary pattern of this syndrome but similarities between cases reported by year 2000 seem to suggest autosomal or x-linked recessive inheritance or possibly a dominant mutation caused by mosaicism as causes of this syndrome.

Some researchers suggest that HGF is transmitted as a Mendelian trait since both autosomal dominant and autosomal recessive transmission has been reported since the early 1970s. (SOURCE 1) In more recent scientific literature, there is evidence in which pedigree analyses confirm autosomal dominant, autosomal recessive or even as X-linked inherited cases of the HGF trait.

In 2002, researchers described the SOS1 gene and proved for the first time that a single-nucleotide–insertion mutation of the SOS1 gene on codon 1083 is the preliminary cause of HGF1 in humans. (Source 1) Later on in 2010, there was a case study done on a 16-year-old male with severe gingival overgrowth, almost covering all teeth. Researchers approached this issue with periodontics - a partial gingivectomy and flap surgery. This case study concluded that surgery followed by regular follow-ups is a good way to treat HGF despite the fact that the risks of re-occurrence of the condition remain high.

Even more recently, a study was done in 2013 on a family that showed history of autosomal recessive inheritance of HGF. The study did not dismiss the return of HGF after treatment but did claim that general surgical intervention after scaling and root planning of teeth supplemented with good oral hygiene is good enough to prevent the re-occurrence of HGF. This case study also acknowledged how HGF can be part of a multi-system syndrome associated with disorders such as Zimmermann Laband syndrome (ear, nose, bone, and nail defects with hepatosplenomegaly), Rutherford syndrome (microphthalmia, mental retardation, athetosis, and hypopigmentation), Murray-Puretic Drescher syndrome and Ramon syndrome.

Genitopatellar Syndrome is an autosomal dominant inheritance where the mutation in the KAT6B causes the syndrome. The KAT6B gene is responsible for making an enzyme called histone acetyltransferase which functions in regulating and making of histone which are proteins that attach to DNA and give the chromosomes their shape. The function of histone acetyltransferase produced from KAT6B is unknown but it is considered as a regulator of early developments. There is little known about how the mutation in the KAT6B causes the syndrome but researchers suspects that the mutations occur near the end of the KAT6B gene and causes it to produce shortened acetyltransferase enzyme. The shortened enzyme alters the regulation of other genes. On the other hand, the mutation of KAT6B leading to the specific features of genitopatellar syndrome is still not surely proven.

HGF1 - Caused by a mutation in the SOS1 gene localized on chromosome 2p21-p22

HGF2 - Caused by a mutation in the SOS1 gene localized on chromosome 5q13-q22

Mutations in the RE1-silencing transcription factor (REST) gene can also cause this syndrome.

- Non genetic

HGF may also be caused by unwanted side effects of pharmacological agents like phenytoin, ciclosporin, and some calcium-channel blockers, meaning HGF is a disease that can be drug-induced. However, there is little next to no research done in this area to support the claim.

- Inflammation

- Hormonal Imbalance

- Neoplasia

- More commonly associated with an autosomal dominant gene inheritance

- Multi-system syndromes: Zimmerman-Laband syndrome, Jones syndrome, Ramon syndrome, Rutherford syndrome, juvenile hyaline fibromatosis, systemic infantile hyalinosis, and mannosidosis

- Some unknown causes

Presenting at birth, features of the disorder include moderately severe IUGR, microcephaly, craniosynostosis, moderately severe post uterine growth retardation, deafness, deep set eyes, cryptorchidism, truncal obesity and acanthosis nigricans, small teeth, prognathism, dislocated radial heads without generalized skeletal dysplasia, however, tall vertebrae, moderate mental retardation, hypothyroidism, insulin resistance, hypoparathyroidism.

Genitopatellar syndrome is a rare disorder with characteristic craniofacial features, congenital flexion contractures of the lower limbs, absent or abnormal patellae, urogenital anomalies, and severe psychomotor retardation.

In 2012, it was shown that mutations in the gene KAT6B cause the syndrome.

Bangstad syndrome is a severe, inherited congenital disorder associated with abnormalities of the cell membrane.

It was characterized in 1989.

In 2012, a 5-generation Dutch family consisting of 7 males and 7 females with Wilson-Turner Syndrome. These individuals had some characteristics that differed from the stated phenotype mentioned by Wilson. These individuals have a larger stature, head, and chin, in addition to coarse facial features. Unlike the females in Wilson's study, these females shown signs of being affected, although less severe than their male counterparts. None of the men could live on their own. Studies verified that the phenotype of the disorder range on a large scale and can affect everyone differently. This research group also used next-generation sequencing of the X chromosome exome to identify the HDAC8 gene mutation

There is also ongoing research to determine the cause of the decreased or low androgen levels. It is studying the possible disturbance of the hypothalamic-pituitary-gonadal axis because of the low levels of androgen are combined with normal levels of FSH and LH.

Young–Simpson syndrome (YSS) is a rare congenital disorder with symptoms including hypothyroidism, heart defects, facial dysmorphism, cryptorchidism in males, hypotonia, mental retardation and postnatal growth retardation.

Other symptoms include transient hypothyroidism, macular degeneration and torticollis. The condition was discovered in 1987 and the name arose from the individuals who first reported the syndrome. An individual with

YSS has been identified with having symptoms to a similar syndrome known as Ohdo Blepharophimosis syndrome, showing that it is quite difficult to diagnose the correct condition based on the symptoms present. Some doctors therefore consider these syndromes to be the same.

The mode of inheritance has had mixed findings based on studies undertaken. One study showed that the parents of an individual with YSS are unrelated and phenotypically normal, indicating a sporadic mutation, thus making it difficult to base the cause of the condition on genetic makeup alone. However, another study was done of an individual with YSS who had first cousins as parents, giving the possibility of autosomal recessive inheritance.

One known cause of hypertrichosis cubiti is Wiedemann-Steiner syndrome.

Research on the risk for developing schizophrenia in Ashkenazi Jews and other populations showed that 3q29 microdeletion syndrome leads to a significant higher rate of schizophrenia.

Unlike Borjeson-Forssman-Lehmann syndrome, a disorder that was determined to be very similar to WTS, the individuals with Wilson–Turner syndrome do not develop cataracts or hypermetropia later in life. By far, the most debilitating part of this disorder is intellectual disability. Many of the other symptoms are more easily managed through hormone treatment, proper diet and exercise, and speech therapy.

While many cases of HPMRS are caused by mutations in the PIGV gene, there may be genetic heterogeneity in the spectrum of Mabry syndrome as a whole. PIGV is a member of the molecular pathway that synthesizes the glycosylphosphatidylinositol anchor. The loss in PIGV activity results in a reduced anchoring of alkaline phosphatase to the surface membrane and an elevated alkaline phosphatase activity in the serum.

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.

Wiedemann–Rautenstrauch (WR) syndrome , also known as neonatal progeroid syndrome, is an autosomal recessive progeroid syndrome.

WR was first reported by Rautenstrauch and Snigula in 1977; and the earliest reports made subsequently have been by Wiedemann in 1979, by Devos in 1981, and Rudin in 1988. There have been over 30 cases of WR.

WR is associated with abnormalities in bone maturation, and lipids and hormone metabolism. Affected individuals exhibit intrauterine and postnatal growth retardation, leading to short stature and an aged appearance from birth. They have physical abnormalities including a large head (macrocephaly), sparse hair, prominent scalp veins, inward-folded eyelid (entropion), widened anterior fontanelles, hollow cheeks (malar hypoplasia), general loss of fat tissues under the skin (lipoatrophy), delayed tooth eruption, abnormal hair pattern (hypotrichosis), beaked nose, mild to severe mental retardation and dysmorphism.

Marfan lipodystrophy syndrome (MFLS) has sometimes been confused with Wiedemann–Rautenstrauch syndrome, since the Marfanoid features are progressive and sometimes incomplete. MFLS is caused by mutations near the 3'-terminus of "FBN1" that cause a deficiency of the protein hormone asprosin and progeroid-like symptoms with reduced subcutaneous white adipose tissue.

The RASopathies are developmental syndromes caused by germline mutations (or in rare cases by somatic mosaicism) in genes that alter the Ras subfamily and mitogen-activated protein kinases that control signal transduction, including:

- Capillary malformation-AV malformation syndrome

- Autoimmune lymphoproliferative syndrome

- Cardiofaciocutaneous syndrome

- Hereditary gingival fibromatosis type 1

- Neurofibromatosis type 1

- Noonan syndrome

- Costello syndrome, Noonan-like

- Legius syndrome, Noonan-like

- Noonan syndrome with multiple lentigines, formerly called LEOPARD syndrome, Noonan-like

Hyperphosphatasia with mental retardation syndrome, HPMRS, also known as Mabry syndrome, has been described in patients recruited on four continents world-wide. Mabry syndrome was confirmed to represent an autosomal recessive syndrome characterized by severe mental retardation, considerably elevated serum levels of alkaline phosphatase, hypoplastic terminal phalanges, and distinct facial features that include: hypertelorism, a broad nasal bridge and a rectangular face.

Hypertrichosis cubiti (also known as "hairy elbow syndrome") is a cutaneous condition characterized by multiple terminal hairs on both elbows in children.

X-linked hypertrichosis is a hereditary disorders characterized by generalized congenital hypertrichosis.

In general, children with a small isolated nevus and a normal physical exam do not need further testing; treatment may include potential surgical removal of the nevus. If syndrome issues are suspected, neurological, ocular, and skeletal exams are important. Laboratory investigations may include serum and urine calcium and phosphate, and possibly liver and renal function tests. The choice of imaging studies depends on the suspected abnormalities and might include skeletal survey, CT scan of the head, MRI, and/or EEG.

Depending on the systems involved, an individual with Schimmelpenning syndrome may need to see an interdisciplinary team of specialists: dermatologist, neurologist, ophthalmologist, orthopedic surgeon, oral surgeon, plastic surgeon, psychologist.