During the G0/G1 phase of the cell cycle, DNA damage can trigger a CSB-dependent recombinational repair process that uses an RNA (rather than DNA) template.The premature aging features of CS are likely due, at least in part, to the deficiencies in DNA repair (see DNA damage theory of aging). Diagnosis
People with this syndrome have smaller than normal head sizes (microcephaly), are of short stature (dwarfism), their eyes appear sunken, and they have an "aged" look. They often have long limbs with joint contractures (inability to relax the muscle at a joint), a hunched back (kyphosis), and they may be very thin (cachetic), due to a loss of subcutaneous fat. Their small chin, large ears, and pointy, thin nose often give an aged appearance. The skin of those with Cockayne syndrome is also frequently affected: hyperpigmentation, varicose or spider veins (telangiectasia), and serious sensitivity to sunlight are common, even in individuals without XP-CS. Often patients with Cockayne Syndrome will severely burn or blister with very little heat exposure. The eyes of patients can be affected in various ways and eye abnormalities are common in CS. Cataracts and cloudiness of the cornea (corneal opacity) are common. The loss of and damage to the nerves of the optic nerve, causing optic atrophy, can occur. Nystagmus, or involuntary eye movement, and pupils that fail to dilate demonstrate a loss of control of voluntary and involuntary muscle movement. A salt and pepper retinal pigmentation is also a typical sign.
They also compared Cockayne syndrome to what is now known as Hutchinson–Gilford progeria syndrome (HGPS), then called progeria, due to the advanced aging that characterizes both disorders. Types
CS Type I, the "classic" form, is characterized by normal fetal growth with the onset of abnormalities in the first two years of life. Vision and hearing gradually decline. The central and peripheral nervous systems progressively degenerate until death in the first or second decade of life as a result of serious neurological degradation. Cortical atrophy is less severe in CS Type I.
CS Type II is present from birth (congenital) and is much more severe than CS Type 1. It involves very little neurological development after birth. Death usually occurs by age seven. This specific type has also been designated as cerebro-oculo-facio-skeletal (COFS) syndrome or Pena-Shokeir syndrome Type II. COFS syndrome is named so due to the effects it has on the brain, eyes, face, and skeletal system, as the disease frequently causes brain atrophy, cataracts, loss of fat in the face, and osteoporosis. COFS syndrome can be further subdivided into several conditions (COFS types 1, 2, 3 (associated with xeroderma pigmentosum) and 4). Typically patients with this early-onset form of the disorder show more severe brain damage, including reduced myelination of white matter, and more widespread calcifications, including in the cortex and basal ganglia. CS Type III, characterized by late-onset, is typically milder than Types I and II. Often patients with Type III will live into adulthood.