This is a very rare situation, in which the extra digit is on the ring, middle or index finger. Of these fingers, the index finger is most often affected, whereas the ring finger is rarely affected.

This type of polydactyly can be associated with syndactyly, cleft hand and several syndromes.

Polysyndactyly presents various degrees of syndactyly affecting fingers three and four.

This is a less common situation, in which the affectation is on the side of the hand towards the thumb. Radial polydactyly refers to the presence of an extra digit (or extra digits) on the radial side of the hand. It is most frequent in Indian populations and it is the second most common congenital hand disorder. The incidence of radial polydactyly is reported as 1 in every 3,000 live births. The clinical features of radial polydactyly will depend upon the extent of duplication.

Radial polydactyly varies from a barely visible radial skin tag to complete duplication. Thumb polydactyly varies from barely visible broadening of the distal phalanx to full duplication of the thumb including the first metacarpal.

Radial polydactyly is frequently associated with several syndromes.

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.

The triphalangeal thumb has a different appearance than normal thumbs. The appearance can differ widely; the thumb can be a longer thumb, it can be deviated in the radio-ulnar plane (clinodactyly), thumb strength can be diminished. In the case of a five fingered-hand it has a finger-like appearance, with the position in the plane of the four fingers, thenar muscle deficiency, and additional length. There is often a combination with radial polydactyly.

Very frequent signs

- Abnormal gastrointestinal tract

- Absent pectoral muscles

- Brachydactyly (Short fingers)

- Dextrocardia

- Diaphragmatic hernia/defect

- Humerus absent/abnormal

- Liver/biliary tract anomalies

- Maternal diabetes

- Oligodactyly/missing fingers

- Radius absent/abnormal

- Rhizomelic micromelia (relatively shorter proximal segment of the limbs compared to the middle and the distal segments)

- Sparsity or abnormality of axillary hair on affected side

- Syndactyly of fingers (webbing)

- Ulna absent/abnormal

- Upper limb asymmetry

- Abnormal rib

- Simian crease on affected side

Frequent signs

- Hypoplastic/absent nipples

- Scapula anomaly

Occasional signs

- Agenesis/hypoplasia of kidneys

- Encephalocele/exencephaly

- Abnormal morphology of hypothalamic-hypophyseal axis

- Abnormal function of hypothalamic-hypophyseal axis

- Microcephaly

- Preaxial polydactyly

- Ureteric anomalies (reflux/duplex system)

- Vertebral segmentation anomaly

Generally, triphalangeal thumbs are non-opposable. In contrast to most people with opposable thumbs, a person suffering from TPT cannot easily place his or her thumb opposite the other four digits of the same hand. The opposable thumb's ability to effortlessly utilize fingers in a "pinch" formation is critical in precision gripping. For the thumb to adequately grip, certain thumb criteria must be met (e.g. suitable position and length, stable joints and good thenar muscle strength). Because triphalangeal thumbs cannot easily oppose and do not possess many of the optimal qualities found in most opposable thumbs, they tend to cause the hand to be less effective in use and, therefore, prove to be more problematic in daily life.

Additional findings that may be present in HFGS according to the latest research are:

- Limited metacarpophalangeal flexion of the thumb or limited ability to oppose the thumb and fifth finger

- Hypoplastic thenar eminences

- Medial deviation of the great toe (hallux varus), a useful diagnostic sign when present

- Small great toenail

- Fifth-finger clinodactyly, secondary to a shortened middle phalanx

- Short feet

- Altered dermatoglyphics of the hands; when present, primarily involving distal placement of the axial triradius, lack of thenar or hypothenar patterning, low arches on the thumbs, thin ulnar loops (deficiency of radial loops and whorls), and a greatly reduced ridge count on the fingers

Radiographic findings

- Hypoplasia of the distal phalanx and first metacarpal of the thumbs and great toes

- Pointed distal phalanges of the thumb

- Lack of normal tufting of the distal phalanges of the great toes

- Fusions of the cuneiform to other tarsal bones or trapezium-scaphoid fusion of the carpals

- Short calcaneus

- Occasional bony fusions of the middle and distal phalanges of the second, third, fourth, or fifth toes

- Delayed carpal or tarsal maturation

- Metacarpophalangeal profile reflecting shortening of the first metacarpal, the first and second phalanges, and the second phalanx of the second and fifth digits

Urogenital Defects

Females may have the following:

- Vesicoureteral reflux secondary to ureteric incompetence

- Ectopic ureteral orifices

- Trigonal hypoplasia

- Hypospadiac urethra

- Subsymphyseal epispadias

- Patulous urethra

- Urinary incontinence (related to structural anomalies and weakness of the bladder sphincter muscle)

- Small hymenal opening

- Various degrees of incomplete Müllerian fusion with or without two cervices or a longitudinal vaginal septum

Males may have the following:

- Retrograde ejaculation (related to structural anomalies and weakness of the bladder sphincter muscle)

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

Diagnosing the congenital clasped thumb is difficult in the first three to four months of life, as it is normal when the thumb is clutched into the palm in these first months.

Diagnoses that cause the same flexion or adduction abnormalities of the thumb are:

- Congenital clasped thumb

- Congenital Trigger thumb (flexion of the interphalangeal joint) - Trigger finger

- Spasticity: overstimulation of muscles

Syndrome associated flexion-adduction of the thumb:

- Freeman-Sheldon syndrome (a congenital, heritable affection of the face, the hands, the feet and some joints)

- Distal arthrogryposis

- MASA syndrome

- X-linked hydrocephalus

- Adducted thumb syndrome

- Waardenburg syndrome

- Whistling face syndrome (Freeman-Sheldon syndrome)

- Digitotalar dysmorphism

- Multiple pterygium syndrome

Hand-foot-genital syndrome (HFGS) is characterized by limb malformations and urogenital defects. Mild bilateral shortening of the thumbs and great toes, caused primarily by shortening of the distal phalanx and/or the first metacarpal or metatarsal, is the most common limb malformation and results in impaired dexterity or apposition of the thumbs. Urogenital abnormalities include abnormalities of the ureters and urethra and various degrees of incomplete Müllerian fusion in females and hypospadias of variable severity with or without chordee in males. Vesicoureteral reflux, recurrent urinary tract infections, and chronic pyelonephritis are common; fertility is normal.

Poland syndrome, named after British surgeon Alfred Poland, is a rare birth defect characterized by underdevelopment or absence of the chest muscle (pectoralis) on one side of the body, and usually also webbing of the fingers (cutaneous syndactyly) of the hand on the same side (the ipsilateral hand). In most affected individuals, the missing part is the large section of the muscle that normally attaches to the upper arm on one side and the breastbone (sternum) on the other. Other abnormalities may occur on the affected side of the torso. In some cases, additional muscles in the chest wall, side, and shoulder are missing or underdeveloped.

There may also be rib cage abnormalities, such as shortened ribs, and the ribs may be noticeable due to less fat under the skin (subcutaneous fat). Breast and nipple abnormalities may also occur, and underarm (axillary) hair is sometimes sparse or abnormally placed. In most cases, the abnormalities in the chest area do not cause health problems or affect movement. Poland syndrome most often affects the right side of the body, and occurs more often in males than in females.

It is usually considered a unilateral condition. Some have claimed that the term can be applied in bilateral presentation, but others recommend using alternate terminology in those cases.

Heart-hand syndromes are a group of rare diseases that manifest with both heart and limb deformities.

, known heart-hand syndromes include Holt–Oram syndrome, Berk–Tabatznik syndrome, heart-hand syndrome type 3, brachydactyly-long thumb syndrome, patent ductus arteriosus-bicuspid aortic valve syndrome and heart hand syndrome, Slovenian type.

The thumb contains five groups of muscle and/or tendons:

1. Extensor tendons (to stretch the thumb)

2. Flexor muscles/tendons (to bend the thumb)

3. Abductor muscles/tendons (to move the thumb outwards)

4. Adductor muscle (to move the thumb inwards)

5. Opposing muscles (to move the thumb opposite the small finger)

In order for the thumb to maintain a normal position, a strict balance between these groups is required. Weak or absent extensors and/or abductors (the extensor pollicis brevis tendon, the extensor pollicis longus tendon or, rarely, the abductor pollicis longus tendon), can cause a disbalance, leading to an abnormal position of the thumb: congenital clasped thumb. There is also the possibility that two tendons are affected simultaneously.

The following tendon deviations can induce congenital clasped thumb:

- The flexor tendons are too short (the thumb is drawn into the palm)

- The abductor tendons are hypoplastic or absent

- The extensor tendons are hypoplastic or absent

Furthermore, a tight thumb web space (the area between thumb and index finger) can contribute to congenital clasped thumb. The thumb cannot be properly abducted (moved outwards), if the web space is too tight.

To summarize, the causes of congenital clasped thumbs may vary between patients and can sometimes be a combination of the preceding components. Treatment should be tailored to all occurring components in order to achieve good results.

Sometimes babies born with choanal atresia also have other abnormalities:

- coloboma

- heart defects

- mental retardation

- growth impairment

- others (see also CHARGE syndrome)

Also any condition that causes significant depression of the nasal bridge or midface retraction can be associated with choanal atresia. Examples include the craniosynostosis syndromes such as Crouzon syndrome, Pfeiffer syndrome, Treacher Collins and Antley-Bixler syndrome.

The following is a list of symptoms that have been associated with Roberts syndrome:

- Bilateral Symmetric Tetraphocomelia- a birth defect in which the hands and feet are attached to shortened arms and legs

- Prenatal Growth Retardation

- Hypomelia (Hypoplasia)- the incomplete development of a tissue or organ; less drastic than aplasia, which is no development at all

- Oligodactyly- fewer than normal number of fingers or toes

- Thumb Aplasia- the absence of a thumb

- Syndactyly- condition in which two or more fingers (or toes) are joined together; the joining can involve the bones or just the skin between the fingers

- Clinodactyly- curving of the fifth finger (little finger) towards the fourth finger (ring finger) due to the underdevelopment of the middle bone in the fifth finger

- Elbow/Knee Flexion Contractures- an inability to fully straighten the arm or leg

- Cleft Lip- the presence of one or two vertical fissures in the upper lip; can be on one side (unilateral) or on both sides (bilateral)

- Cleft Palate- opening in the roof of the mouth

- Premaxillary Protrusion- upper part of the mouth sticks out farther than the lower part of the mouth

- Micrognathia- small chin

- Microbrachycephaly- smaller than normal head size

- Malar Hypoplasia- underdevelopment of the cheek bones

- Downslanting Palpebral Fissures- the outer corners of the eyes point downwards

- Ocular Hypertelorism- unusually wide-set eyes

- Exophthalmos- a protruding eyeball

- Corneal Clouding- clouding of the front-most part of the eye

- Hypoplastic Nasal Alae- narrowing of the nostrils that can decrease the width of the nasal base

- Beaked Nose- a nose with a prominent bridge that gives it the appearance of being curved

- Ear Malformations

- Intellectual disability

- Encephalocele (only in severe cases)- rare defect of the neural tube characterized by sac-like protrusions of the brain

Mortality is high among those severely affected by Roberts syndrome; however, mildly affected individuals may survive to adulthood

It can be unilateral or bilateral.

- Sometimes, a unilateral choanal atresia is not detected until much later in life because the baby manages to get along with only one nostril available for breathing.

- Bilateral choanal atresia is a very serious life-threatening condition because the baby will then be unable to breathe directly after birth as babies are obligate nasal breathers (they mainly use their noses to breathe). In some cases, this may present as cyanosis while the baby is feeding, because the oral air passages are blocked by the tongue, further restricting the airway. The cyanosis may improve when the baby cries, as the oral airway is used at this time. These babies may require airway resuscitation soon after birth.

Heart-hand syndrome type 1 is more commonly known as Holt–Oram syndrome. Is the most prevalent form of heart-hand syndrome.

It is an autosomal dominant disorder that affects bones in the arms and hands (the upper limbs) and may also cause heart problems. The syndrome includes an absent radial bone in the arms, an atrial septal defect, and a first degree heart block.

Classification of radial dysplasia is practised through different models. Some only include the different deformities or absences of the radius, where others also include anomalies of the thumb and carpal bones. The Bayne and Klug classification discriminates four different types of radial dysplasia. A fifth type was added by Goldfarb et al. describing a radial dysplasia with participation of the humerus. In this classification only anomalies of the radius and the humerus are taken in consideration. James and colleagues expanded this classification by including deficiencies of the carpal bones with a normal distal radius length as type 0 and isolated thumb anomalies as type N.

Type N: Isolated thumb anomaly

Type 0: Deficiency of the carpal bones

Type I: Short distal radius

Type II: Hypoplastic radius in miniature

Type III: Absent distal radius

Type IV: Complete absent radius

Type V: Complete absent radius and manifestations in the proximal humerus

The term absent radius can refer to the last 3 types.

Facial femoral syndrome is a rare congenital disorder. It is also known as femoral dysgenesis, bilateral femoral dysgenesis, bilateral-Robin anomaly and femoral hypoplasia-unusual facies syndrome. The main features of this disorder are underdeveloped thigh bones (femurs) and unusual facial features.

ONH may be found in isolation or in conjunction with myriad functional and anatomic abnormalities of the central nervous system. Nearly 80% of those affected with ONH will experience hypothalamic dysfunction and/or impaired development of the brain, regardless of MRI findings or severity of ONH.

ONH can be unilateral (in one eye) or bilateral (in both eyes), although it presents most often bilaterally (80%). Because the unilateral cases tend to have better vision, they are typically diagnosed at a later age than those with bilateral ONH. Visual acuity can range from no light perception to near-normal vision.

Children diagnosed with ONH generally present with vision problems which include nystagmus (involuntary movement of the eyes), which tends to develop at 1 to 3 months and/or strabismus (inability to align both eyes simultaneously), manifested during the first year of life.

The majority of children affected experience improvement in vision during the first few years of life, though the reason for this occurrence is unknown. There have been no reported cases of decline in vision due to ONH.

The diagnosis is based on the combination of unusual facial features and the dysplastic or absent femurs.

Diagnosis may be made antenatally.

Radial dysplasia, also known as radial club hand or radial longitudinal deficiency, is a congenital difference occurring in a longitudinal direction resulting in radial deviation of the wrist and shortening of the forearm. It can occur in different ways, from a minor anomaly to complete absence of the radius, radial side of the carpal bones and thumb. Hypoplasia of the distal humerus may be present as well and can lead to stiffnes of the elbow. Radial deviation of the wrist is caused by lack of support to the carpus, radial deviation may be reinforced if forearm muscles are functioning poorly or have abnormal insertions. Although radial longitudinal deficiency is often bilateral, the extent of involvement is most often asymmetric.

The incidence is between 1:30,000 and 1:100,000 and it is more often a sporadic mutation rather than an inherited condition. In case of an inherited condition, several syndromes are known for an association with radial dysplasia, such as the cardiovascular Holt-Oram syndrome, the gastrointestinal VATER syndrome and the hematologic Fanconi anemia and TAR syndrome. Other possible causes are an injury to the apical ectodermal ridge during upper limb development, intrauterine compression, or maternal drug use (thalidomide).

The most prominent and extensively documented findings of Weismann-Netter-Stuhl syndrome are on plain radiographs of the bones. Findings include bilateral and symmetric anterior bowing of both tibiae and fibulae, lateral bowing of the tibiae, femoral bowing, and squaring of iliac and pelvis bones.

Weismann-Netter-Stuhl syndrome, also known as Weismann-Netter Syndrome or more technically by the term tibioperoneal diaphyseal toxopachyosteosis, is a rare disorder characterized by bowing of the lower legs and an abnormal thickening of thinner bone in the leg.

The main sign is anterior bowing and posterior cortical thickening of the diaphyses of both the tibiae and fibulae. It is thought to be inherited in an autosomal dominant fashion, and is most often bilateral and symmetric in nature. Associated features include dwarfism and mild intellectual disability, as well as a process known as tibialization of the fibulae, which involves thickening and enlargement of these bones to an extent resembling the tibiae. The combination of the presence of tibialization of the fibulae, which is highly specific for the disorder, and the absence of laboratory abnormalities ruling out alternative diagnoses including rickets, essentially confirms the diagnosis.