Cockayne syndrome
Meaning of Cockayne syndrome: A rare inherited disorder of DNA repair marked by failure to grow, sun sensitivity and a progressive loss of skills.
Definition of Cockayne syndrome
Cockayne syndrome is a rare inherited disorder in which cells cannot properly repair damage to the DNA strands they are actively reading. Growth slows severely after the first months of life, the head stays small, the skin burns readily in sunlight, and hearing, sight and nervous system function decline over time. Features resembling premature aging give the condition its recognizable appearance.
What goes wrong at the level of the cell?
DNA is damaged constantly, by ultraviolet light and by the ordinary chemistry of a working cell. Several repair systems exist. The one affected here handles damage found on a strand that a cell is in the middle of copying into a working message, and it clears the obstruction so the process can continue. Faults in either of two genes, most often, leave that system unable to act. The cell stalls, and cells that cannot resolve the block die. Tissues with a high demand for continuous protein production, especially nerve tissue, are the worst affected.
What are the features?
| Area | Findings |
|---|---|
| Growth | Very short stature, low weight, small head |
| Nervous system | Loss of acquired skills, unsteadiness, stiffness |
| Eyes | Cataracts and degeneration of the retina |
| Hearing | Progressive loss |
| Skin | Severe sunburn from limited exposure |
| Appearance | Sunken eyes, thin nose, loss of fat under the skin |
How is it inherited and diagnosed?
Inheritance is recessive, meaning a child must receive a faulty copy of the gene from both parents, who are typically unaffected carriers. Each pregnancy of such a couple carries a one in four chance. The pattern of features prompts the suspicion, and genetic testing confirms it. A laboratory test measuring how well a person's cells recover their protein production after ultraviolet exposure can also demonstrate the repair defect directly. Severity varies, and recognized forms range from one apparent at birth to a milder late onset type.
How does it differ from other repair disorders?
Xeroderma pigmentosum involves a related repair pathway and also causes extreme sun sensitivity, but with a very high rate of skin cancer. This condition produces the burning without that cancer risk, an unexpected difference that has taught researchers a good deal about how the two pathways diverge. There is no treatment for the underlying genetic fault, so care is directed at nutrition, vision, hearing, mobility and protection from sunlight, and life expectancy is significantly shortened.
Used in a sentence
Cockayne syndrome was confirmed by genetic testing after severe growth failure and photosensitivity.
Good to know
Sun sensitivity in this condition is not accompanied by the high skin cancer rate seen in xeroderma pigmentosum, despite both arising from faults in related DNA repair pathways.