17q21.31 Micro deletion Syndrome

17q21.31 micro deletion syndrome is a very rare genetic condition in which a tiny piece is missing from one of the 46 chromosomes, in this case the 17th chromosome, The tiny missing bit increases the possibility of developmental and speech delay and learning difficulties. 

Symptoms of 17q21.31 are that Some babies are born small and light for dates. In the early days, when feeding is difficult, growth may falter but it usually normalises. In time, some children catch up, but others remain short compared with other family members and a few are extremely short.

Young babies are very floppy, have difficulty feeding, often require tube feeding, babies will smile, hold their head up, sit, stand, move and walk and talk late and will have difficulty making the sounds of speech, and will always require support with learning.

Children and adults look more like others with 17q21.31 than like other members of their family. Some children have silvery hair but this usually darkens with age. Eyes are most typically blue. Children often have a tubular or pear-shaped nose with a bulbous tip that becomes more obvious with age, an open mouth and protruding tongue.

Other common features include a high forehead; upslanting eyes, sometimes with tiny skinfolds at the inner corners; and large ears. In time, the face may lengthen and features lose their delicacy.

Growth

Some babies are born small and light for dates. In the early days, when feeding is difficult, growth may falter but it usually normalises. In time, some children catch up, but others remain short compared with other family members and a few are extremely short.

Birth or development defects

When people have been described with a particular disorder, some conditions that may be typical for the disorder may not be listed. Conversely, conditions may be listed that are not typical. Most children and adults have no important birth defects. Boys are commonly born with undescended testicles. One baby in three has an anomaly of the kidneys or urinary system. Around a quarter are born with a hole in the heart, which may resolve naturally or be corrected by surgery. One baby in four is born with clicky or dislocated hips, requiring stabilisation to improve the development of the hip joint. Brain scans in more than one in three showed wide ventricles (the fluid-filled spaces in the brain). Three babies had a split in the roof of the mouth and one in four a hollowed chest. Two babies were born with craniosynostosis (premature fusion of some of the bones of the skull) and one had her skull reshaped surgically. The same child has glycogen storage disease type O, a very rare liver disorder.

Hands and feet.

Unusual features of the hands and feet are common in people with this chromosome disorder. Most are cosmetic - such as having long, slender fingers or slender lower limbs - but talipes (club foot) has occurred, where the feet need repositioning to make walking easier. A teenager and an adult each developed hallux valgus where the big toe tilts towards the smaller toes and a bony ‘bunion’ appears on the inside of the foot. Wearing comfortable wide-fitting shoes and padding the bony lump may deal with any discomfort. If that is not sufficient, a chiropodist can advise and if necessary, the joint can be corrected. These two individuals also developed pes cavus (an excessively high arch). Cavus feet tend to be stiffer than normal and may not take pressure as well as normal feet, aching if weightbearing for a while. Basic foot care is important and it may be hard to find well-fitting shoes. If necessary, an orthopaedic foot surgeon can advise about surgical correction. A further boy had flat and painful feet and had successful surgery (subtalar arthrodesis) to fuse bones in the heel. As a teenager he walks independently and wears shaped insoles to relieve pain.

Medical concerns

Children and adults are generally healthy. Seizures occur in around half but these usually seem to be easy to control with medication and some children outgrow them. A squint (strabismus) and long sight are also common and at least one child had cataracts removed from both eyes. Hearing appears usually to be normal, but a slight hearing loss in both ears was found in one child and a mild-to-moderate conductive and sensory loss in another, a low immune system is recorded too.

Behaviour.

Parents report that their children are friendly, co-operative and like to make others laugh. Some have a tendency to develop ‘fixations’ on items like foods or favourite films. Some children also have sensory issues.

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