Cockayne Syndrome, Type B
Patient Information
Characteristics
Background and History
Edward A. Cockayne, a London physician specializing in hereditary diseases of children, first described features of this syndrome in a book published in 1933. It is one of several hereditary forms of genetic disease in which features of premature aging are present. Three types of Cockayne syndrome have been described based on the age of onset and clinical course.
Clinical Correlations
Neurologic and physical abnormalities are usually evident at birth or during the neonatal period. The head is usually small and infants are short. They usually do not develop normal milestones of normal development. They also feed poorly and there is a constant risk of aspiration with respiratory infections common. Physical growth is extremely slow and some never grow beyond the size of a 6 month old child. The joints may become contracted which further impedes physical mobility. The skin is highly sensitive to the sun's rays. Cataracts are common and the eyes appear ‘sunken’. Tremors, or shakiness, are common.
Genetics
Inheritance
This is an autosomal recessive disorder which requires the presence of two mutations to cause disease. Parents are not affected but carry a single copy of the mutation. If both parents carry the mutation, they can expect that 25% of their offspring will have Cockayne syndrome.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis is often made by pediatricians and medical geneticists at birth or soon after based on the clinical features and the progression of symptoms. Most patients die before the age of 5 years. No specific treatment is available but physical and supportive therapy can be helpful. Protection from the sun is important.
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