Median nail dystrophy (also known as "Dystrophia unguis mediana canaliformis," "Median canaliform dystrophy of Heller," and "Solenonychia") consists of longitudinal splitting or canal formation in the midline of the nail, a split which often resembles a fir tree, occurring at the cuticle and proceeding outward as the nail grows.

Thumbs, which are the most commonly involved, usually show an enlarged lunula resulting probably from repeated pressure applied on the base of the nail.

Hair abnormalities are very prominent in majority of the cases of TDO. Kinky/curly hair that is unusually dry and easily sheds is present at birth. In 80% of cases, the hair has a more relaxed appearance by adolescence. The presence of this hair texture type is a defining characteristic between a diagnosis of TDO verses amelogenesis imperfecta with hypomaturation. Additionally, in TDO the nails are usually abnormally thin, brittle, and split frequently. Cranial deficiencies are marked by the presence of having a long skull relative to its width, or protrusive foreheads due to increased thickness of the cranial bones and premature closing of the associated sutures in the skull. The long bones in the body (arms, legs) are also abnormally long and tend to fracture very easily. Osteosclerosis, commonly seen in TDO cases is characterized by an increase in bone density, affecting the skull and the mastoid process located behind the jawbone on the skull, as well as a shortened ramus seen in people with TDO. There are no known pathological problems associated with hair and bone changes in people with this disease. Changes in the long bones tend to appear later in development, but changes in the teeth appear once the teeth being to form, called primary dentition. The hair and bone abnormalities are evaluated radiographically during initial diagnosis, and visually during the course of the disease. Radiographic exams may be repeated if there is suspect of fracture.

Oligodactyly (from the Ancient Greek "oligos" meaning "few" and δάκτυλος "daktylos" meaning "finger") is the presence of fewer than five fingers or toes on a hand or foot.

It is quite often incorrectly called "hypodactyly", but the Greek prefixes and are used for scales (e.g. in hypoglycaemia and hypercholesterolemia). This as opposed to or scales, where and should be used (e.g. in oligarchy and polygamy). Oligodactyly is therefore the opposite of polydactyly. Very rare, this medical condition usually has a genetic or familial cause.

Oligodactyly is sometimes a sign or symptom of several syndromes including Poland syndrome and Weyer Ulnar Ray Syndrome. It is a type of Dysmelia.

Ectrodactyly is an extreme instance of oligodactyly, involving the absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly are often described as "claw-like" and may include only the thumb and one finger (usually either the little finger, ring finger, or a syndactyly of the two) with similar abnormalities of the feet.

People with oligodactyly often have full use of the remaining digits and adapt well to their condition. They are not greatly hindered in their daily activities, if at all. Even those with the most extreme forms are known to engage in tasks that require fine control, such as writing and bootmaking as well as working as a cab driver.

Vadoma people of Zimbabwe have a high frequency of oligodactyly.

Patient with skeletal open bites that accompany dental open bites may have Adenoid faces or Long face syndrome. They are said to have what is known as "Hyperdivergent Growth Pattern" which includes characteristics such as:

- Increased Lower Anterior Facial Height

- Occlusal plane diverges after the 1st molar contact

- May accompany dental open bite

- Narrow nostrils with upturned nose

- Dolicofacial or Leptoprosopic face pattern

- Constricted maxillary arch

- Bilateral Posterior Crossbite

- High and narrow palatal vault

- Presence of crowding in teeth

- Mentalis muscle strain upon forcibly closing of lips

- Possible gummy smile with increased interlabial gap

Cephalometric analysis features of skeletal open bite may include:

- Increased Frankfurt-Mandibular Plane angle

- Steep Occlusal Plane Angle

- Increased SN-MP Angle

- Short Mandibular ramus

- Increased mandibular body length

- Downward and backward position of mandible

- Increased gonial angle

- Proclined upper incisors, retroclined or upright lower incisors

- Posterior part of maxilla is tipped downwards

- Posterior facial height equals 1/2 of anterior facial height

- Increased hard tissue Lower Anterior Facial Height

- Increased total anterior facial height

- Short mandibular ramus

Viken Sassouni developed Sassouni analysis which indicates that patient's with long face syndrome have 4 of their bony planes (mandibular plane, occlusal plane, palatal plane, SN plane) steep to each other.

Open bite malocclusion can happen due to several reasons. It may be genetic in nature, leading to a skeletal open bite or can be caused by functional habits which may lead to dental open bite. In the earlier age, open bite may occur due to a transitional change from primary to the permanent dentition. Some factors that may cause an open bite are:

- Tongue thrusting

- Thumb sucking

- Long-term usage of Pacifier

- Macroglossia

- Airway obstruction

- Adenoid hypertrophy

- Nasal concha Hypertrophy

Ectodermal dysplasia is characterized by absent sweat glands resulting in dry (hypohydrotic), often scale-like skin, sparse and usually coarse scalp hair that is often blonde, sparse eyebrows and eyelashes, and small brittle nails. In addition, abnormalities of ectodermal derivatives, neuroectodermal derivatives, and mesectodermal derivatives are often found. The ectodermal derivative abnormalities can affect the epidermis including mammary, pituitary and sweat glands, as well as hairs, dental enamel, nails, lens, and the internal ear. Neuroectodermal derivatives that can be affected include sensory placodes, cutaneous pigmental cells, and hair buds. Mesectodermal derivatives affected can include the dermis, hypodermis, dentin, head muscles and conjunctival cells, cervicofacial vascular endothelial cells, and part of the maxillofacial skeleton.

The hypohydrotic symptoms of ectodermal dysplasia described above are evidenced not only in the skin of affected individuals, but also in their phonation and voice production. Because the vocal folds may not be as hydrated as is necessary during the adduction phase of vocal fold vibration (due to lack of lubrication), a complete seal may not be accomplished between the folds and mucosal wave movement may be disrupted. This results in air escapement between the folds and the production of breathy voice, which often accompanies the skin abnormalities of ectodermal dysplasia.

Tricho-dento-osseous syndrome (TDO) is a rare, systemic, autosomal dominant genetic disorder that causes defects in hair, teeth, and bones respectively. This disease is present at birth. TDO has been shown to occur in areas of close geographic proximity and within families; most recent documented cases are in Virginia, Tennessee, and North Carolina. The cause of this disease is a mutation in the DLX3 (distal-less 3) gene, which controls hair follicle differentiation and induction of bone formation. One-hundred percent of patients with TDO suffer from two co-existing conditions called enamel hypoplasia and taurodontism in which the abnormal growth patterns of the teeth result in severe external and internal defects. The hair defects are characterized as being rough, course, with profuse shedding. Hair is curly and kinky at infancy but later straightens. Dental defects are characterized by dark-yellow/brownish colored teeth, thin and/or possibly pitted enamel, that is malformed. The teeth can also look normal in color, but also have a physical impression of extreme fragility and thinness in appearance. Additionally, severe underbites where the top and bottom teeth fail to correctly align may be present; it is common for the affected individual to have a larger, more pronounced lower jaw and longer bones. The physical deformities that TDO causes become more noticeable with age, and emotional support for the family as well as the affected individual is frequently recommended. Adequate treatment for TDO is a team based approach, mostly involving physical therapists, dentists, and oromaxillofacial surgeons. Genetic counseling is also recommended.

Specific types of additional body parts include:

- Accessory breast – one or more additional breasts

- Accessory spleen – one or more additional spleens

- Cervical rib – an additional rib

- Diphallia - Having two penes/penises.

- Hermaphroditism – having both sexes' sex organs

- Hyperdontia – additional teeth

- Pelvic digit – a bony growth in the soft tissue of the pelvic region

- Polycephaly – an extra head

- Polydactyly – additional fingers or toes

- Polymelia — an extra arm or leg.

- Polyorchidism – having three or more testicles

- Supernumerary bones – these additional bones are fairly common, particularly in the feet, and are frequently mistaken for fractures on x-rays.

- Supernumerary kidney – a third kidney

- Supernumerary nipples – an additional nipple

- Supernumerary phantom limbs – where the brain acts as though a limb were there, but it is not.

- Syndactyly – webbing between the fingers or toes

- Uterus didelphys – two vaginal canals and/or uteri

Ectrodactyly involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand–split foot malformation (SHFM). The hands and feet of people with ectrodactyly are often described as "claw-like" and may include only the thumb and one finger (usually either the little finger, ring finger, or a syndactyly of the two) with similar abnormalities of the feet.

Ectodermal dysplasia describes abnormalities of structures derived from the embryonic ectoderm. These abnormalities affect both the superficial ectodermal layer, as well as the mesectodermal layer constituted by the neural crest.

Ectrodactyly, split hand, cleft hand, derived from the Greek "ektroma" (abortion) and "daktylos" (finger) involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly are often described as "claw-like" and may include only the thumb and one finger (usually either the little finger, ring finger, or a syndactyly of the two) with similar abnormalities of the feet.

It is a rare form of a congenital disorder in which the development of the hand is disturbed. It is a type I failure of formation – longitudinal arrest. The central ray of the hand is affected and usually appears without proximal deficiencies of nerves, vessels, tendons, muscles and bones in contrast to the radial and ulnar deficiencies. The cleft hand appears as a V-shaped cleft situated in the centre of the hand. The digits at the borders of the cleft might be syndactilyzed, and one or more digits can be absent. In most types, the thumb, ring finger and little finger are the less affected parts of the hand. The incidence of cleft hand varies from 1 in 90,000 to 1 in 10,000 births depending on the used classification. Cleft hand can appear unilateral or bilateral, and can appear isolated or associated with a syndrome.

Split hand/foot malformation (SHFM) is characterized by underdeveloped or absent central digital rays, clefts of hands and feet, and variable syndactyly of the remaining digits. SHFM is a heterogeneous condition caused by abnormalities at one of multiple loci, including SHFM1 (SHFM1 at 7q21-q22), SHFM2 (Xq26), SHFM3 (FBXW4/DACTYLIN at 10q24), SHFM4 (TP63 at 3q27), and SHFM5 (DLX1 and DLX 2 at 2q31). SHFM3 is unique in that it is caused by submicroscopic tandem chromosome duplications of FBXW4/DACTYLIN. SHFM3 is considered 'isolated' ectrodactyly and does not show a mutation of the tp63 gene.

Supernumerary body parts are most commonly a congenital disorder involving the growth of an additional part of the body and a deviation from the body plan. Body parts may be easily visible or hidden away, such as internal organs.

Many additional body parts form by the same process as conjoined twins: the zygote begins to split but fails to completely separate. This condition may also be a symptom of repeated occurrences of continuous inbreeding in a genetic line.

Fibrochondrogenesis is a congenital disorder presenting several features and radiological findings, some which distinguish it from other osteochondrodysplasias. These include: fibroblastic dysplasia and fibrosis of chondrocytes (cells which form cartilage); and flared, widened

long bone metaphyses (the portion of bone that grows during childhood).

Other prominent features include dwarfism, shortened ribs that have a appearance, micrognathism (severely underdeveloped jaw), macrocephaly (enlarged head), thoracic hypoplasia (underdeveloped chest), enlarged stomach, platyspondyly (flattened spine), and the somewhat uncommon deformity of tongue (in which the tongue appears split, resembling that of a reptile).

Chimney sweep's cancer, also called soot wart, is a squamous cell carcinoma of the skin of the scrotum. It has the distinction of being the first reported form of occupational cancer, and was initially identified by Percivall Pott in 1775. It was initially noticed as being prevalent amongst chimney sweeps.

Disfigurement is the state of having one's appearance deeply and persistently harmed medically, such as from a disease, birth defect, or wound. General societal attitudes towards disfigurement have varied greatly across cultures and over time, with cultures possessing strong social stigma against it often causing psychological distress to disfigured individuals. Alternatively, many societies have regarded some forms of disfigurement in a medical, scientific context where someone having ill will against the disfigured is viewed as anathema. In various religious and spiritual contexts, disfigurement has been vaoriously described as being as a punishment from the divine for sin (such as Yahweh's defacement of Cain for Abel's murder in Judaism), as being (such as Paul of the New Testament's arguments about Christ's sufferings) caused by supernatural forces of hate and evil against the good and just, which will be later atoned for, or as being without explanation "per se" with people just having to endure.

The topic has been frequently commented on and referred to in a great many forms of fictional media as well. Villainous examples include the iconic fiend The Joker from various DC Comics and the mysterious figure with a "red right hand" from the song of the same name by band Nick Cave and the Bad Seeds. Heroic examples include Daredevil, a crime-fighter who was rendered blind (from Marvel Comics), and the compassionate character Edward Scissorhands from the film of the same name.

Fibrochondrogenesis is a rare autosomal recessive form of osteochondrodysplasia, causing abnormal fibrous development of cartilage and related tissues.

It is a lethal rhizomelic (malformations which result in short, underdeveloped limbs) form of dwarfism, exhibiting both skeletal dysplasia (malformations of bone) and fibroblastic dysplasia (abnormal development of fibroblasts, specialized cells that make up fibrous connective tissue, which plays a role in the formation of cellular structure and promotes healing of damaged tissues). Death caused by complications of fibrochondrogenesis occurs in infancy.

Trachyonychia, sometimes called sandpapered nails, is a condition characterized by rough accentuated linear ridges (longitudinal striations) on the nails of the fingers and toes. When the condition occurs on all the twenty nails of the fingers and toes, it is known as twenty-nail dystrophy, most evident in childhood, favoring males.

Trachyonychia causes the nails to become opalescent, thin, dull, fragile, and finely longitudinally ridged, and, as a result, distally notched. It can be a manifestation of lichen planus, psoriasis, alopecia areata, immunoglobulin A deficiency, atopic dermatitis, and ichthyosis vulgaris.

"The longitudinal striations can occur as a normal part of the aging process", and not until the nails start to thin and get a sandpaper look is the condition called trachonychia. The nails are opalescent and frequently are brittle and split at the free margin. There has been evidence of the condition as a cutaneous manifestation of lichen planus. It has also been associated with other diseases such as eczema, psoriasis, alopecia areata, and atopic dermatitis. Trachonychia is often seen in vitiligo patients – suggesting that they are more susceptible to this condition.

Conditions that can cause disfigurement include:

- severe acne

- acromegaly

- amniotic band constriction

- amputation

- argyria

- birthmarks

- burns

- cancer

- cataracts

- circumcision

- cleft lip

- eczema

- elephantiasis

- erysipelas

- gangrene

- gigantomastia

- gynecomastia

- keloids

- leprosy

- necrosis

- McCune–Albright syndrome

- neurofibromatosis

- noma

- paralysis

- proteus syndrome

- radiation poisoning

- scalping

- scars

- smallpox

- severe strabismus

- synkinesis

- Syphilis

- vitiligo

- severe warts

Plastic surgery or reconstructive surgery is available in many cases to disfigured people. Some health insurance companies and government health care systems cover plastic surgery for these problems when they do not generally cover plastic surgery for what is labeled as "cosmetic purposes".

The term "disfigurement" is sometimes used pejoratively to describe the results of intentional body modification. Scarification and other forms of such modification will sometimes be referred to as such by neutral parties or by advocates of the processes as well. Many types of body modification are subject to strong social debate as such.

There are several classifications for cleft hand, but the most used classification is described by Manske and Halikis see table 3. This classification is based on the first web space. The first web space is the space between the thumb and the index.

Table 3: Classification for cleft hand described by Manske and Halikis

Among the symptoms(and signs) for this condition are the following:

- lack of apparent hair growth

- hair appears patchy

- hair breaks easily close to scalp

- hair may have thickenings or nodes in the shaft

- ends of hair thinned or split

- whitish discoloration of hair tips

- hair breaks easily at tips

People with Aarskog-Scott syndrome often have distinctive facial features, such as widely spaced eyes (hypertelorism), a small nose, a long area between the nose and mouth (philtrum), and a widow's peak hairline. They frequently have mild to moderate short stature during childhood, but their growth usually catches up with that of their peers during puberty. Hand abnormalities are common in this syndrome and include short fingers (brachydactyly), curved pinky fingers (fifth finger clinodactyly), webbing of the skin between some fingers (cutaneous syndactyly), and a single crease across the palm. Other abnormalities in people with Aarskog-Scott syndrome include heart defects and a split in the upper lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate).

Most males with Aarskog-Scott syndrome have a shawl scrotum, in which the scrotum surrounds the penis instead of hanging below. Less often, they have undescended testes (cryptorchidism) or a soft out-pouching around the belly-button (umbilical hernia) or in the lower abdomen (inguinal hernia).

The intellectual development of people with Aarskog-Scott syndrome varies widely. Some may have mild learning and behavior problems, while others have normal intelligence. In rare cases, severe intellectual disability has been reported.

Burn scar contracture refers to the tightening of the skin after a second or third degree burn. When skin is burned, the surrounding skin begins to pull together, resulting in a contracture. It needs to be treated as soon as possible because the scar can result in restriction of movement around the injured area.

Trichorrhexis nodosa is a defect in the hair shaft characterized by thickening or weak points (nodes) that cause the hair to break off easily. This group of conditions contributes to the appearance of hair loss, lack of growth, and damaged-looking hair.

Favid (of "favus" Latin for "honeycomb" or tinea favosa) is a disease usually affecting the scalp, but occurring occasionally on any part of the skin, and even at times on mucous membranes.

The word “Favid” is more used than French word “favus”, which is close to the Latin etymology.

In medicine, split hand syndrome is a neurological syndrome in which the hand muscles on the side of the thumb (lateral, thenar eminence) appear wasted, whereas the muscles on the side of the little finger (medial, hypothenar eminence) are spared. Anatomically, the abductor pollicis brevis and first dorsal interosseous muscle are more wasted than the abductor digiti minimi.

If lesions affecting the branches of the ulnar nerve that run to the wasted muscles are excluded, the lesion is almost sure to be located in the anterior horn of the spinal cord at the C8-T1 level. It has been proposed as a relatively specific sign for amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease). It can also occur in other disorders affecting the anterior horn, such as spinal muscular atrophy, Charcot-Marie-Tooth disease, poliomyelitis and progressive muscular atrophy. A slow onset and a lack of pain or sensorial symptoms are arguments against a lesion of the spinal root or plexus brachialis. To an extent, these features can also be seen in normal aging (although technically, the apparent muscle wasting is sarcopenia rather than atrophy).

The term split hand syndrome was first coined in 1994 by a researcher from the Cleveland Clinic called Asa J. Wilbourn.

Aarskog–Scott syndrome is a rare disease inherited as X-linked and characterized by short stature, facial abnormalities, skeletal and genital anomalies. This condition mainly affects males, although females may have mild features of the syndrome.

The Aarskog–Scott syndrome (AAS) is also known as the Aarskog syndrome, faciodigitogenital syndrome, shawl scrotum syndrome and faciogenital dysplasia.