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.

MDM is most common on the Dalmatian island of Mljet (or "Meleda"), thought to be because of a founder effect. It is of autosomal recessive inheritance. It may be caused by a mutation on the "SLURP1" gene, located on chromosome 8.

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

Tooth and nail syndrome (also known as "Hypodontia with nail dysgenesis," and "Witkop syndrome") is a rare disorder, first described in 1965, characterized by nails that are thin, small, and friable, and which may show koilonychia at birth.

It is associated with "MSX1".

Meleda disease (MDM) or "mal de Meleda", also called Mljet disease, keratosis palmoplantaris and transgradiens of Siemens, (also known as "Acral keratoderma," "Mutilating palmoplantar keratoderma of the Gamborg-Nielsen type," "Palmoplantar ectodermal dysplasia type VIII", and "Palmoplantar keratoderma of the Norrbotten type") is an extremely rare autosomal recessive congenital skin disorder in which dry, thick patches of skin develop on the soles of the hands and feet, a condition known as palmoplantar hyperkeratosis.

Lelis syndrome it is a genetic disorder, a rare condition with dermatological and dental findings characterized by the association of ectodermal dysplasia (hypotrichosis and hypohidrosis) with acanthosis nigricans. Other clinical features may include palmoplantar hyperkeratosis, nail dystrophy, intellectual deficit, disturbances of skin pigmentation (perioral and periorbital hyperpigmentation, vitiligo, and perinevic leukoderma) and hypodontia. Transmission is autosomal recessive.

CHILD syndrome is a rare disorder with only 60 recorded cases worldwide thus far in literature.

CHILD syndrome is not fatal unless there are problems with the internal organs. The most common causes of early death in people with the syndrome are cardiovascular malformations. However, central nervous system, skeletal, kidney, lung, and other visceral defects also contribute significantly.

Pure hair-nail type ectodermal dysplasia is a genetic mutation in the "hair matrix and cuticle keratin KRTHB5 gene" that causes ectodermal dysplasia of hair and nail type. Manifestations of this disorder include onychodystrophy and severe hypotrichosis. It represents as an autosomal dominant trait.

Coffin–Siris Syndrome is a rare genetic disorder that causes developmental delays and absent fifth finger and toe nails.

There had been 31 reported cases by 1991. The numbers of occurrence since then has grown and is reported to be around 80.

The differential includes Nicolaides–Baraitser syndrome.

Cooks syndrome is a hereditary disorder which is characterized in the hands by bilateral nail hypoplasia on the thumb, index finger, and middle finger, absence of fingernails (anonychia) on the ring finger and little finger, lengthening of the thumbs, and bulbousness of the fingers. In the feet, it is characterized by absence of toenails and absence/hypoplasia of the distal phalanges. In the second study of this disorder, it was found that the intermediate phalanges, proximal phalanges, and metacarpals were unaffected.

The disorder was first described by Cooks "et al." in 1985 after being discovered in two generations of one family. It was proposed that the inheritance of the disorder is autosomal dominant. A second family, this with three affected generations, confirmed that the inheritance of the disorder is autosomal dominant. Although several genetic disorders exist which can cause anonychia and onychodystrophy, such disorders often cause other anomalies such as deafness, mental retardation, and defects of the hair, eyes, and teeth. Cooks syndrome is not known to cause any such anomalies.

In 1999, a pair of siblings was found with brachydactyly type B. Because the disorder primarily affected the nails and distal phalanges, the research group concluded that brachydactyly type B and Cooks syndrome are the same disorder. However, in 2007, a 2-year-old girl was found with symptoms consistent with both brachydactyly type B and Cooks syndrome. It was found that the two syndromes were distinct clinically, radiologically, and genetically.

Dyskeratosis congenita (DKC), also called Zinsser-Cole-Engman syndrome, is a rare progressive congenital disorder with a highly variable phenotype. The entity was classically defined by the triad of abnormal skin pigmentation, nail , and leukoplakia of the oral mucosa, but these components do not always occur. DKC is characterized by short telomeres. Some of the manifestations resemble premature aging (similar to progeria). The disease initially mainly affects the skin, but a major consequence is progressive bone marrow failure which occurs in over 80%, causing early mortality.

A review from 2000 stated that life expectancy was reduced because of a tendency to develop cancer relatively early as well as deaths due to infections related to immunodeficiency.

Autosomal recessive inheritance is the most likely, but sporadic mutations and autosomal dominant cases may also occur.

This syndrome has been associated with mutations in the ARID1B gene.

Mutations in SOX11 are associated to this syndrome.

The diagnosis is generally based on the presence of major and at least one minor clinical sign and can be confirmed by molecular genetic testing of the causative genes. Recent studies revealed that fifth finger nail/distal phalanx hypoplasia or aplasia is not a mandatory finding.

Monilethrix (also referred to as beaded hair) is a rare autosomal dominant hair disease that results in short, fragile, broken hair that appears beaded. It comes from the Latin word for necklace ("monile") and the Greek word for hair ("thrix").

Severe congenital onychogryphosis affecting all twenty nailbeds has been recorded in two families who exhibit the dominant allele for a certain gene. Congenital onychogryphosis of the fifth toe (the little toe) is fairly common, but asymptomatic and seldom brought to the attention of medical professionals. Rather, it is brought to the attention of manicurists who routinely file the clawed toenail flat.

DKC can be characterized by cutaneous pigmentation, premature graying, of the nails, leukoplakia of the oral mucosa, continuous lacrimation due to atresia of the lacrimal ducts, often thrombocytopenia, anemia, testicular atrophy in the male carriers, and predisposition to cancer. Many of these symptoms are characteristic of geriatrics, and those carrying the more serious forms of the disease often have significantly shortened lifespans.

In racquet nails (also known as brachyonychia, nail en raquette, and racquet thumb), the nail plate is flattened, the end of the thumb is widened and flattened, and the distal phalanx is abnormally short. In racquet nails, the width of the nail bed and nail plate is greater than their length. The condition is painless and asymptomatic.

Racquet nails usually occur on one or both thumbs, but may appear on all fingers and toes. It may be genetic, inherited as an autosomal-dominant trait, or acquired. Genetic disorders associated with racquet nail include Larsen syndrome, Brooke–Spiegler syndrome, Rubinstein–Taybi syndrome, Hajdu–Cheney syndrome, cartilage–hair hypoplasia, pycnodysostosis, acrodysostosis, and brachydactylia.

Acquired racquet nail is associated with acroosteolysis and psoriatic arthropathy. Acquired racquet nail may also be diagnostic of bone resorption in hyperparathyroidism.

Racquet nail often presents with other nail conditions such as onycholysis, koilonychia, pachyonychia, Muehrcke's lines, leuconychia, and half-and-half nails. Cosmetic surgery can be used to improve the appearance of the nails.

Although it has been described in families, it has been suggested that it might not have a genetic link.

Zimmermann–Laband syndrome (ZLS), also known as Laband–Zimmermann syndrome, and Laband's syndrome, is an extremely rare autosomal dominant congenital disorder.

Some recommend avulsion of the nail plate with surgical destruction of the nail matrix with phenol or the carbon dioxide laser, if the blood supply is good.

Onychomatricoma is a cutaneous condition characterized by a distinctive tumor of the nail matrix.

This nail disease can mimic many nail problems and should be examined and biopsied by a dermatologist. In particular, a main concern is the malignant and destructive potential that may exist.

Symptoms include gingival fibromatosis, associated with hypoplasia of the distal phalanges, nail dysplasia, joint hypermobility, and sometimes hepatosplenomegaly. The nose and pinnae are usually large and poorly developed, which gives the individuals with the syndrome abnormal facial characteristics. Mental retardation may also occur. Both males and females are equally affected. Gingival fibromatosis is usually present at birth or appears short after. The term Zimmermann–Laband was coined by Carl Jacob Witkop in 1971.

People with yellow nail syndrome have been found to have a moderately reduced lifespan compared to people without the condition.

Omphalocele has been described in two patients with Apert syndrome by Herman T.E. et al. (USA, 2010) and by Ercoli G. et al. (Argentina, 2014). An omphalocele is a birth defect in which an intestine or other abdominal organs are outside of the body of an infant because of a hole in the bellybutton area. However, the association between omphalocele and Apert syndrome is not confirmed yet, so additional studies are necessary.