Substitution of glutamic acid by valine

# What disorder is a result of a genetic mutation causing the substitution of glutamic acid by a valine and results in dental radiographs with enlarged marrow spaces?
A. Cystic fibrosis
B. Muscular dystrophy
C. Polio
D. Sickle-cell anemia

The correct answer is: D. Sickle cell anemia.

Sickle-cell anemia is an inherited disease in which the red blood cells, normally disc-shaped, become crescent-shaped. As a result, they function abnormally and cause small blood clots. These clots give rise to recurrent painful episodes called "sickle cell pain crises." Sickle-cell anemia (also called sickle-cell disease) is the result of the production of abnormal hemoglobin (Hemoglobin S) due to a genetic defect. lt is carried as a trait by  10% of African Americans and 0.2% have sickle-cell anemia. It is more common in females and usually clinically manifests itself before the age of 30. The typical signs of anemia are present. The patient is weak, short of breath, and easily fatigued. Muscle and joint pains are common.

Dental radiographs are often of diagnostic value: marrow spaces are markedly enlarged because of the loss of many trabeculae; the trabeculae, which are present, are often abnormally prominent. Occasionally, osteosclerotic areas are noted in the midst of large radiolucent marrow spaces. However, the lamina dura and the teeth are unaffected.

Note: The gene defect is a known mutation of a single nucleotide (thymine for an adenine) of the beta-globin gene, which results in glutamic acid to be substituted by valine. Sickle cell anemia occurs when a person inherits two abnormal genes (one from each parent). If a person inherits one abnormal gene for the disease, they have what is called sickle cell trait. The life span of red blood cells is reduced from 120 to 20 days.

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