DEAR DR. DONOHUE: I am an African-American woman who is curious about sickle cell anemia. I know it is a disease of African-Americans, but I would like to know why. In fact, I would like to know more about it, because my knowledge of it is nonexistent. – S.S.

ANSWER: Sickle cell anemia is mostly found in blacks, but it is not limited to them. Asian Indians, people whose ethnic heritage comes from countries on the east coast of the Mediterranean, and a few Arabs can suffer from it. Sickle red blood cells give these people protection from malaria infection.

For a child to have sickle cell anemia, both of his or her parents must carry one gene. A one-gene carrier has sickle cell trait. About 10 percent of blacks have the trait. Carriers have few to no symptoms. When a carrier man marries a carrier woman, their children have a one in four chance of coming down with sickle cell anemia. That child will have gotten one sickle cell gene from the mother and one from the father.

As is true of all anemias, sickle cell anemia has a dearth of red blood cells. The signs of a red blood cell deficit are constant tiredness and shortness of breath upon little exertion.

In addition, when people with sickle cell anemia suffer a drop in blood oxygen, their red blood cells transform into cells having the shape of a sickle. Sickle cells stick to each other and obstruct blood flow. That is a sickle cell crisis, and it is most painful. Bones hurt. Kidney function deteriorates. Skin ulcers often appear, and such ulcers are difficult to treat.

Hydroxyurea is a drug that lessens the number of sickle cell crises that a patient has.

Some sickle cell patients benefit from bone marrow transplants or stem cell transplants. Such procedures should be done in large hospitals that have an expert staff.

DEAR DR. DONOHUE: I talked with a friend in Arizona who told me that she has lung fungus. I thought that the only fungal infections were things like athlete’s foot and ringworm. What is a lung fungus infection?

ANSWER: There are many, many fungal lung infections, and fungal infections can happen to just about every body organ. Because most of them are uncommon, their names sound strange. They are not, however, rare.

In the mid-Atlantic, Southeast and Central United States, a not-uncommon fungal lung infection is histoplasmosis.

Blastomycosis is another fungal lung infection found in the same areas and in Canada.

In the Southwest – Arizona, California and Texas – a common fungal infection that primarily infects the lungs is coccidioidomycosis (kok-SID-ee-OID-oh-my-COE-suss). In some cities in that locale, the infection rate is as high as 90 percent. You have not heard its name because most of the time such an infection produces no symptoms.

It can, however, cause pneumonia, and that is a nasty infection. It is difficult to treat, and treatment drugs are often difficult on the patient.

I apologize for the name. A more pronounceable name for this fungal infection is “valley fever” – the “valley” referring to the San Joaquin Valley.

DEAR DR. DONOHUE: What is the significance of slender black lines under the fingernail tips? Someone looked at my nails, pointed the black lines out to me and said they indicate heart trouble. My father died at 42 from a heart attack, and this information has made me nervous. Is there any truth to it? – K.L.

ANSWER: Black lines about the width of a strand of black thread under the fingernail tips can be splinter hemorrhages. They are indications of one kind of heart disease, the heart valve infection known as bacterial endocarditis.

Believe me. You do not have bacterial endocarditis. You would be deathly ill if you did. Your lines most likely are the result of nail trauma. You can forget them.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.