Hemoglobin SC Disease - An Overview

Introduction:

Hemoglobin SC disease is also called sickle cell hemoglobin C or sickle hemoglobin C disease. It is a type of genetic blood disorder classified under sickle cell anemia. Sickle cell anemia is a blood disease that is present at birth. It changes the shape of red blood cells because of a problem with the gene that makes hemoglobin in red blood cells. Hemoglobin, which is a protein, has the function of carrying oxygen-rich blood to the various tissues of the body. Sickle cell anemia gets its name from the shape of the red blood cells, which change from being round to having a C-shaped curve, like a sickle.

What Is Hemoglobin SC Disease?

A normal red blood cell comprises millions of molecules of a protein called hemoglobin. And this hemoglobin is made up of two alpha subunits produced by two alpha globin genes called HBA1 and HBA2 and two beta subunits produced by the beta-globin gene called HBB. The genetic defect in the beta-globin gene produces two abnormal types of hemoglobin called hemoglobin S (HbS) and hemoglobin C (HbC). It is called hemoglobin SC disease when a person has both types of abnormal hemoglobin in their red blood cells.

How Is Hemoglobin SC Disease Inherited?

It is an autosomal recessive disorder. A person may carry the mutated gene but not have the disease. So they are called carriers of the disease. They will have one mutated gene from one parent, either hemoglobin S or hemoglobin C, and another normal gene from the other parent, hemoglobin A. So they can have hemoglobin A, AC, or AS in their blood. But if a parent has hemoglobin AS and another has hemoglobin AC, they can pass on their defective gene to their child with hemoglobin SC. So, with each pregnancy, there is a 25% chance that the parents, who are carriers of the defective gene, will pass on hemoglobin SC, a 50% chance that the child will also be a carrier of hemoglobin AS or AC and a 25% chance that the child will inherit a normal hemoglobin A.

What Are the Signs and Symptoms of Hemoglobin SC Disease?

Infants affected by this disease start showing symptoms at six months. But it may vary from case to case.

• Fever: Fever in babies with hemoglobin SC disease will have serious infections.

• Splenic Sequestration: Blood passes in and out of the spleen. In the spleen of an infant affected with this disease, the sickled cells are trapped inside the organ and do not move out. This accumulation produces symptoms like swollen stomach, irritability, and excessive sleepiness. It is a very serious problem for babies.

• Anemia: Sickle cells are not as long-lived as normal blood cells. Hence, there is a reduction in blood count, which causes mild anemia. An acute condition of increased breakdown of blood cells that can cause severe anemia is called a hemolytic crisis.

• Pain in the Arms, Legs, and Back: The sickle cells are stiff, sticky, and fragile. They do not move smoothly along the blood vessels. They have a higher tendency to stick together and form clogs. This causes severe arm and leg pain and is called a "pain crisis" or "vaso-occlusive crisis."

• Jaundice: As the sickle cells are destroyed easily and faster, they accumulate more waste products in the blood. These waste products cause jaundice which leads to the yellowing of the white portion of the eyes and skin.

• Swollen hands and feet: It is often the first symptom in babies. Hands and feet are warm and sensitive to touch.

• Skin problems.

• Tiredness or weakness.

• Eye and vision problems.

• Delayed growth.

• Frequent infections.

How Is Hemoglobin SC Disease Diagnosed?

• Patient History: A detailed history of symptoms and clinical evaluation will help diagnose the disease.

• Blood Tests: Complete blood count is measured. It shows mild anemia with hemoglobin ranging from 6-8 g/dl. The peripheral blood smear shows curved-shaped sickle cells.

• High-Performance Liquid Chromatography or Hemoglobin Electrophoresis: A blood test measures the number of different types of hemoglobin present in the blood.

• Genetic Tests: An affected individual's DNA is tested for the defective beta-globin gene, which gives an accurate diagnosis. The gene location is on chromosome 11, where valine replaces glutamic acid in the 6th position to produce hemoglobin S and lysine replaces glutamic acid to form hemoglobin C. Any closely related family member is tested to identify whether an individual is a carrier of a defective gene.

• Prenatal Screening:

  • Chorionic Villus Sampling: A small piece of placenta is extracted at the 11th week of pregnancy.

  • Amniocentesis: Amniotic fluid around the developing fetus is tested during the 16th week of pregnancy.

What Is the Treatment for Hemoglobin SC Disease?

1. Medications used to control the symptoms are:

• • Hydroxyurea: This drug reduces the frequency of pain crises. The trigger factors that can cause a crisis should be identified and avoided.
  • Voxelotor is used to prevent the formation of sickled cells.
  • L-glutamine therapy can prevent complications related to sickle cell.
  • Crizanlizumab-tmca drug helps to control the acute episodes of pain during a crisis.

2. Blood transfusions are required to replace the lost blood levels due to anemia.

3. Bone marrow transplantation is performed on a healthy donor who is usually genetically related to the patient, such as siblings or family members. It involves transplanting the affected person’s bone marrow with a healthy one, which will produce normal hemoglobin and perform better bodily functions.

4. Gene Therapy: At present, this treatment option is under research. The mutated gene is corrected.

5. Regular vaccinations should be done to prevent infection or illness, and antibiotics should be given to treat any infection.

6. An active lifestyle with a diet full of essential nutrients and regular exercise can help to minimize the symptoms.

7. Drinking plenty of water and rehydration with intravenous fluids should be practiced, and places or situations that make your body too hot or too cold and that reduce the oxygen levels in the blood, like high altitudes, should be avoided.

8. Folic acid supplements are given.

9. Regular checkups should be done with a cardiologist, ophthalmologist, neurologist, and hematologist to monitor any systemic complications.

What Are the Complications of Hemoglobin SC Disease?

• Acute chest syndrome-fever, chest pain, cough.

• Priapism-painful and persistent erection of the penis.

• Proliferative sickle cell retinopathy or Retinitis proliferans- patients see flashes of light, floaters, or dark shadows due to retinal detachment.

• Sensorineural deafness-Loss of hearing.

• Renal complications-presence of blood in the urine.

• Stroke-sudden weakness, paralysis of one side or both sides of the body, trouble walking, talking, or seeing, and confusion.

• Pulmonary hypertension.

• Pregnancy complications.

• Leg ulcers.

• Deep vein thrombosis.

• Osteonecrosis.

• Neurological complications.

• Cardiac complications.

• Cholelithiasis(gallstones).

Conclusion:

There is no specific cure for this disease. The symptomatic management of the pain and other clinical manifestations is done. Patients require regular checkups with their healthcare providers. This disease is a lifelong condition. Most affected people will have a normal life expectancy and can live into their 50s. They should be careful about acquiring any infections. Researchers are constantly finding ways to treat this disease.