Genes Y Enfermedad

Genes and Disease

Blood and Lymph Diseases

Blood and Lymph Diseases

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Genes and Disease

Blood and Lymph Diseases

As most of the cells in the human body are not in direct contact with the external environment, the
circulatory system acts as a transport system for these cells. Two distinct fluids move through the
circulatory system: blood and lymph. Blood carries oxygen andnutrients to the body's cells, and
carries waste materials away. Blood also carries hormones, which control body processes, and
antibodies, to fight invading germs. The heart is the pump that keeps this transport system moving.
Together, the blood, heart, and blood vessels form the circulatory system.
The lymphatic system (lymph, lymph nodes and lymph vessels) supports the circulatory system
bydraining excess fluids and proteins from tissues back into the bloodstream, thereby preventing
tissue swelling. It also serves as a defense system for the body, filtering out organisms that cause
disease, producing white blood cells, and generating antibodies.
The biochemical make up of lymph — the fluid found in the lymphatic vessels — varies with the
site of origin. For example, lymph frombone marrow, spleen, and thymus have high concentrations
of white blood cells for fighting infection, while lymph from intestines is high in fat that has been
absorbed during digestion. Damage to the lymphatic and circulatory systems leaves the body more
susceptible to sickness and infection, as well as to serious conditions such as cancer.

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Genes and Disease

Blood and Lymph DiseasesAnemia, sickle cell
Sickle cell anemia is the most common inherited

shown to be effective in preventing painful crises.

blood disorder in the United States, affecting about

Hydroxyurea induces the formation of fetal Hb (HbF)

72,000 Americans or 1 in 500 African Americans.

—a Hb normally found in the fetus or newborn—

SCA is characterized by episodes of pain, chronic

which,when present in individuals with SCA, pre-

hemolytic anemia and severe infections, usually

vents sickling. A mouse model of SCA has been

beginning in early childhood.

developed and is being used to evaluate the effec-

SCA is an autosomal recessive disease caused

tiveness of potential new therapies for SCA.

by a point mutation in the hemoglobin beta gene
(HBB) found onchromosome 11p15.4. Carrier frequency of HBB varies significantly around the world,
with high rates associated with zones of high malaria
incidence, since carriers are somewhat protected
against malaria. About 8% of the African American
population are carriers. A mutation in HBB results in
the production of a structurally abnormal hemoglobin
(Hb), called HbS. Hb is an oxygen carrying protein
thatgives red blood cells (RBC) their characteristic
color. Under certain conditions, like low oxygen levels or high hemoglobin concentrations, in individuals
who are homozygous for HbS, the abnormal HbS
clusters together, distorting the RBCs into sickled
shapes. These deformed and rigid RBCs become
trapped within small blood vessels and block them,
producing pain and eventually damagingorgans.
Though, as yet, there is no cure for SCA, a
combination of fluids, painkillers, antibiotics and
transfusions are used to treat symptoms and complications. Hydroxyurea, an antitumor drug, has been

Important Links
Gene sequence
Genome view see gene locations
Entrez Gene collection of gene-related information
BLink [www.ncbi.nlm.nih.gov/sutils/blink.cgi?pid=4504349&org=1] relatedsequences in different organisms

The literature
Research articles online full text
Books online books section
OMIM catalog of human genes and disorders

Websites
Fact Sheet [http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html] from the National Heart, Lung and Blood Institute,
NIH
SCDAA [www.sicklecelldisease.org] Sickle Cell Disease Association of America

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