Parrington 1

Danielle Dyan Parrington

November 1, 2002

Dr. J. Youngblom

Human Genetics

TR 9:40 – 11:07p.m.

Bloom’s Syndrome

        Bloom’s Syndrome (BS) is a rare autosomal recessive disorder characterized by photosensitivity, growth deficiency of prenatal onset, variable degree of immunodeficiency, and increased susceptability to neoplasms of many sites and types.  Bloom’s Syndrome is also known as Congenital Telangiectatic Erythema.  Bloom’s Syndrome is an inherited condition, which means that it is passed from parents to offspring.  Bloom’s Syndrome is caused by a gene that does not function properly.  Individuals with Bloom’s Syndrome have an unusually high number of breaks along their chromosomes.  A chromosome is a structure in our body that contains DNA-genetic material.

History and Background

        Bloom’s Syndrome was first described by New York Dermatologist David Bloom in 1954.  Since then, over 170 individuals have been recognized as being affected.  Because Bloom’s Syndrome is inherited as an autosomal recessive disease, once a couple has an affected child, there is a one in four (twenty-five

Parrington 2

percent) chance for affected offspring in all future pregnancies.  The gene mutation is very rare in most populations.  The gene mutation is more frequent among

Ashkenazi Jews, where the carrier rate may be greater than 1 out of 110, approximately one percent.  Carriers of Bloom’s Syndrome do not manifest symptoms of the disease.

        Individuals affected with Bloom’s Syndrome have inherited two copies of the Bloom's Syndrome gene mutation.  Typically they have certain features which don’t look phenotypically normal.  Most individuals are of an unusually small size at birth but otherwise have a normal degree of maturation.  Most have a very short stature after birth, only rarely reaching five feet in height.  There is a redness of the skin on the face, mainly the lower eyelids, the bridge of the nose and the adjoining upper cheek area, and the lower lip.   There are increased numbers of respiratory tract and ear infections, some of which can be life threatening.   The skin problem, which is aggravated by sun exposure (photosensitivity), varies in severity.  It may be quite disfiguring in some affected individuals, but very mild or even absent in others, however the skin condition improves with age.  Bloom’s syndrome is usually associated with dwarfism.  Diabetes occurs in approximately ten percent of individuals with Bloom’s Syndrome.  Intelligence is usually normal, although mild mental deficiency has occurred in a few affected persons.  Men with Bloom’s Syndrome are usually infertile, and fertility appears to be reduced in women affected with Bloom’s Syndrome.  The risk of cancer is greater than normal throughout life. The variety of sites and types that affect the general population.

Join now!

        Various types of leukemia develop at an average age of twenty-two.  Patients who survive beyond the age of twenty-two develop solid tumors at an average age

Parrington 3

of thirty-five.  These tumors are fortunately sensitive to chemotherapy and radiotherapy.  With an increase in age, resistance to infections gradually improves and so does the skins’ photosensitivity.

Cause of the Disease

          The syndrome is caused by mutation in the gene designated BLM which has been traced to chromosome 15q26.1.  The protein encoded by the normal gene has DNA ligase activity and functions in the maintaining genomic stability. ...

This is a preview of the whole essay