Cockayne Syndrome


Cockayne Syndrome

Description, Causes and Risk Factors:

Cockayne syndrome is a heterogenous syndrome with various authors citing different features in their cases. The consistent clinical features appear to be cachectic dwarfism with a typical prematurely senile facies of sunken eyes, loss of facial adipose tissue, thin nose and large ears, with microcephaly, sensorineural deafness, retinitis pigmentosa, optic atrophy, photosensitivity, ataxia, peripheral neuropathy and mental retardation.

Developmental deterioration begins at about two years of age. Although most cases ultimately become bedridden and develop joint contractures; spasticlty with increased tone, hyperreflexia and extensor plantars do not appear to be a common presenting feature. No mention of spasticlty was made in Cockayne's original cases. Neill and Dingwall's two cases had brisk reflexes but plantars were flexor and limbs stiff but not spastic. In fact other authors have described a decrease in muscle tone and diminished deep tendon reflexes. Fujimoto made mention of a case with clasp-knife spasticlty of the extremities.

Cockayne Syndrome

The etiology of Cockayne's syndrome remains unknown although some authors have suggested inborn errors of metabolism as a possibility. Researchers beleive mutations in the ERCC6 and ERCC8 genes are the cause of Cockayne syndrome. The proteins made by these genes are involved in repairing damaged DNA via the transcription-coupled repair mechanism, particularly the DNA in active genes. If either the ERCC6 or the ERCC8 gene is altered, DNA damage is not repaired. As this damage accumulates, it can lead to malfunctioning cells or cell death.

However, attempts to identify this nature have been unsuccessful to date. The association between Cockayne's syndrome, premature ageing , atherosclerosis and possible inborn error of lipid metabolism have been raised but detailed biochemical analysis of serum lipids, cholesterol, phospholipids and proteins have usually been normal.

The annual incidence of Cockayne Syndrome is close to 1/200,000. Disease severity and the age of onset are variable.

Symptoms:

Patients with Cockayne syndrome usually appear normal at birth.Eventually, they present with a typical facial appearance of a pinched, narrow face and a beaked nose.Mental retardation, microcephaly, and growth failure become evident over time.Photosensitivity and progressive worsening neurologic signs and symptoms of ataxia and quick jerky movements are also noted.

Appearance and habitus in Cockayne syndrome: Microcephaly, a thin nose, and large ears give the patient a Mickey Mouse appearance.Patients may be cachectic.

Skin findings in Cockayne syndrome: Photosensitive eruption with erythema and scale may be observed.Affected areas show hyperpigmentation, telangiectasia, and atrophy.Subcutaneous lipoatrophy results in sunken eyes and an aged progeric appearance.

Diagnosis:

The differential diagnosis mainly includes mitochondrial diseases that may show similar clinical features to those seen in Cockayne Syndrome.

Diagnosis is based on detection of the specific TCR (T-cell receptor) defect that can be identified using a radioactive assay in cultured fibroblasts that measures the recovery of RNA synthesis after UV irradiation. This DNA repair test is a decisive tool for the diagnosis of Cockayne Syndrome. Brain imaging reveals diffuse hypomyelination of the cerebral white matter, calcifications in the putamen, and vermian atrophy.

Prenatal diagnosis can be performed on amniocytes or chorionic cells (using the same cellular test as that employed in fibroblasts) or by direct molecular sequencing if the causative mutations in the family have already been identified.

Treatment:

No specific treatment currently exists for Cockayne Syndrome. Patients should be treated according to the symptoms they have. Physical, occupational, speech, vision, and hearing therapy are most often beneficial.

Consult the following specialists for Cockayne syndrome patients:

  • Ear, nose, and throat specialist for sensorineural deafness.

  • Ophthalmologist for optic atrophy and cataracts.

  • Neurologist for neurologic deterioration, ataxia, and deafness.

  • Dentist for caries.

  • Geneticist for prenatal evaluation and genetic counseling.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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