Thalassemia Management

Introduction

The thalassemias are the most common single-gene disorder in the world and represent a major health burden worldwide.

It is a heterogeneous disorder recessively inherited resulting from various mutations of the genes, which code for the globin chain of Hb, leading to the reduced or absent synthesis of globin chains. When b chain synthesis is affected it is called b-thalassemia.

It was first described by Cooley and Lee in 1925 and the first case of beta-Thalassemia in India was reported by Dr.Mukherjee from Calcutta in 1938.

Thalassemia Management - Epidemiology

• Over 180 million people in the world and around 20 million in India carry the gene for beta-thalassemia.

• One Lac children are born world over with the homozygous state for Thalassemia, (8,000-10,000 children of whom are born in India).

• The frequency of Thalassemia trait is 3-18% in north India to 1-3% or less in the south. A higher frequency noted in certain communities viz. Sindhis, Kutchis, Lohanas, Bhanushalis, Punjabis, Mahars, Agris, Goud Saraswats, Gowdas, etc.

Thalassemia Management - Pathophysiology

• It is characterized by an imbalance in the production of A and B globin polypeptide chains of hemoglobin.

• In alpha -Thalassemia, a chain synthesis is decreased. In beta-thalassemia, beta chain synthesis is decreased. Excessive chains precipitate in the red cell membrane and damage it. It leads to premature red cell destruction both in the bone marrow and peripheral circulation particularly in the reticuloendothelial system of the spleen (ineffective erythropoiesis and hemolysis).

The synthesis of the gamma chain persists after fetal life. Increased fetal hemoglobin (HbF) with its high affinity for oxygen leads to tissue hypoxia, which in turn stimulates erythropoietin secretion leading to both medullary and extramedullary erythropoiesis (expansion of bone marrow space) causing a characteristic hemolytic facies with frontoparietal and occipital bossing, malar prominence and malocclusions of teeth. Complications include distortion of ribs and vertebrae and pathological fracture of the long bones, splenomegaly and its complications (hypersplenism), hepatomegaly, gallstones, and chronic leg ulcers.

Thalassemia Management - Clinical Manifestations

The spectrum of clinical manifestations of Beta-Thalassemia varies widely. One end of the spectrum is the serious homozygous form (Thalassemia Major) that presents in early infancy (6-18 months) with progressive pallor, splenohepatomegaly and bony changes and if left untreated, is invariably fatal during the first few years of life; and the other end of the spectrum is a heterozygous form (thalassemia minor) in which the patient can lead a practically normal life except for mild persistent anemia and have a normal life span. In between these two extremes are forms with varying degrees of clinical manifestations of anemia, splenohepatomegaly and bony changes who maintain their life fairly comfortably and are not dependent on blood transfusion for their survival and are called thalassemia intermedia and are also homozygous.

Thalassemia Management - Diagnosis

• CBC is frequently sufficient to postulate a diagnosis of thalassemia. Peripheral blood smears are diagnostic, with microcytic, hypochromic, poikilocytic, and polychromatic red cells. There is also moderate basophilic stippling with fragmented erythrocytes, target cells and large number of normoblasts and reticulocytes ranges from 2-4%.

• Osmotic fragility reveals reduced fragility.

• Bone marrow examination though not required for diagnosis, shows normoblastic erythroid hyperplasia.

• Hb electrophoresis is diagnostic. Fetal hemoglobin is increased in the patient and HbA2 is over 3.4% in both parents.

• Radiological findings include widening of medulla due to bone marrow hyperplasia, thinning of cortex and trabeculation in the long bones-metacarpals and metatarsals. Skull X-ray shows hair on end appearance.

• Periodic tests for organ dysfunctions is necessary which includes SGOT, SGPT, GGT, Sr.Bilirubin, Sr. Calcium, Sr. Creatinine, etc.

Management of Thalassemic Child

It consists of:

• Confirmation of diagnosis

• Correction of the anemia with repeated RBCs transfusions.

• Removal of iron with iron chelating agents.

• Treatment of complications

• Correction of hemopoiesis by bone marrow transplantation.

• Prevention of the disease by antenatal diagnosis and genetic counselling.

• Pharmacological methods to increase gamma-chain synthesis.

• Gene replacement therapy.

Management of thalassemia major should be preferably done at a comprehensive thalassemia care center with outdoor transfusion facilities. A team approach includes a pediatric hematologist, a blood transfusion specialist, a psychologist, and a social worker, etc. This not only helps the patient and the family to face various medical and psychosocial problems but also helps in the early detection and management of complications.

Transfusion Therapy

Transfusion therapy in Thalassemia has two goals:

• To prevent anemia,

• To suppress endogenous erythropoiesis to avoid ineffective erythropoiesis.

  Blood transfusion is mandatory for all children with Thalassemia major and for those children with Thalassemia intermedia who cannot maintain Hb above 7 gm% or for those who show evidence of growth retardation, severe bony changes, or hypersplenism. Regular blood transfusions are presently the mainstay of treatment of Thalassemia.

When to transfuse:

• Transfusion is started at the time of diagnosis, that is when the child becomes clinically symptomatic.

• Thalassemia intermedia presents a complex therapeutic problem as these children may lead a near-normal life without being transfusion dependent. Occasionally, it may not be clear whether one is dealing with Thalassemia intermedia or major.

• Majority of Thalassemia intermedia can be detected by

  *Age of onset of symptoms is usually more than two years.

  *Increased indirect hyperbilirubinemia of 2 mg/dl or more.

  *High reticulocyte count more than 10% at the time of diagnosis.

  *Hb is usually maintained above 7-10 gm% without blood transfusion.

• If there is a doubt about the diagnosis, it is wiser to follow up these children regularly and transfusion therapy should be started only if Hb drops to less than 6-7 gm%, and then regular transfusions are continued to maintain Hb level above 10-12 gm%.

What to transfuse?

• Transfuse them with triple saline washed packed cells to avoid transfusion reactions as saline washing minimizes reactions due to leucocytes and plasma proteins.

• If the cold centrifuge is required and is not available, simply packed cells may be given.

• Frozen cells: Freezing the RBCs to -80 degree Celsius, with the addition of glycerol to protect RBCs from the damage of freezing and thawing, preserves 2,3-DPG and ATP in the red cells. Thus frozen cells can be stored as long as seven years at -20 degrees Celsius. However, cost and high technology are involved, which do not permit its use even in developed countries.

• Leucocyte filters are also effective in eliminating neutrophils. Various filters available are ImmuGuard 500, Sepsea, Travanol, Ery Pure B, Pal leucocytes filters, which cost around Rs.150-500, and are not reusable. They are superfluous for those patients who have not developed febrile reactions.

How much to transfuse

• Transfusion regimen may be¹ low transfusion regimen where Hb is maintained around 6-10 gm%,²hypertransfusion: Hb level 10-12 gm%, and supertransfusion where Hb is maintained at 12-14 gm%.

• The popular transfusion regimen of today is a hypertransfusion regime that aims at maintaining mean hemoglobin levels at12.5 gm/dl and pre-transfusion level not less than 10 gm%.

• Such a regimen permits normal growth and physical activity, suppresses erythropoiesis, thus preventing skeletal changes and gastrointestinal iron absorption and also inhibits extra-medullary hemopoiesis, thereby preventing splenomegaly and hypersplenism.

• With this regime, the requirement of blood is high only at the start of therapy, and does not produce more iron overload than the low transfusion regime.

• Pre-transfusion Hb level should be high enough to inhibit bone marrow activity i.e. around 9.5-10 gm%.

• post-transfusion Hb should not go above 16 gm/dl, since it can lead to hyperviscosity and its complications.

• When this therapy is started late in life when already hypersplenism has set in, splenectomy becomes mandatory.

Amount and Frequency of transfusion:

• It is desirable that patients receive not more than 10 cc packed cells/kg/day, which raises Hb level by about 3.5 gm/dl. In most of the patients, transfusion of about 10 cc of packed RBC/kg every third week is adequate to maintain Pre-transfusion baseline Hb level at desired 10-11 gm/dl.

  The rate of transfusion should be 5-7 ml/kg body weight/hour to avoid sudden increase in blood volume.

• In patients with cardiac insufficiency, transfusions may have to be given every second week and sometimes every week. - The duration of transfusion should be prolonged by decreasing the rate to 1-3 ml/kg/hr and not more than 5 ml/kg/hour.

How often to transfuse:

• Transfusions should preferably be given on an out-patient basis, at intervals of 2-4 weeks.

• Blood to be transfused should be crossmatched using Coomb's sera to minimize reactions. Blood should be taken from a voluntary donor and should be screened for hepatitis B antigen, HCV, Syphilis, malaria, and HIV.

• The patients should be assessed annually for mean hemoglobin levels maintained overall blood requirement, physical growth and development, evidence of hypersplenism, antibody development, and iron overload. On average, the annual blood requirement is 180-200 ml of blood/kg. However, if the requirement exceeds this level, hypersplenism, or the development of anti-red cell antibodies have to be considered.

Complications of transfusions:

Febrile Reactions: It is seen in 3-20% of patients and may be due to leucocyte or platelet antibodies, antibodies against RBC antigens, allergic reactions to other plasma or blood proteins, or due to pyrogens present in transfused blood. Chills followed by fever may occur within an hour of transfusion or may be delayed for 24 hours. Headache, nausea, and vomiting may be associated.

Febrile reactions usually respond to antipyretic and anti-histaminic agents. Leucocyte filters are also effective in eliminating neutrophils, which are responsible for pyrogenic reactions.

Hemolytic Transfusion Reactions: It occurs in 5-15% of cases. These are due to major or minor blood group mismatch and are characterized by fever, chills, tachycardia, nausea, vomiting, pallor, restlessness, anxiety, flushing of the face, precordial oppression and pain, increased pulse rate and respiratory rate, generalized tingling sensation, pain in back and thigh, shock with cold and clammy skin, cyanosis and collapse. Delirium and convulsions may develop. The most feared complications are acute renal failure, hemorrhagic diathesis due to DIC, and anaphylactic shock, all of which may be of life-threatening proportions. Patients may develop indirect hyperbilirubinemia, hemoglobinemia, hemoglobinuria, reticulocytosis, and positive Coomb's test and can occasionally go into acute renal failure and shock.

On the onset of any early symptoms, transfusion should be stopped immediately. Anything unusual that alarms the mother should be respected. Older children (with Thalassemia) sometimes can even sense that something has gone wrong. As the mother always remembers the blood group of the child, it is a sound policy to show her the label on the bottle before starting the transfusion. For the first fifteen minutes, transfusion should be given slowly so as to detect any reactions at the earliest moment. If facilities are available, all patients should be typed for the common RBC antigens ie Rh, Cc, Dd, Ee, Kell, Kidd, and Duffy (before starting regular transfusion). The monitoring of the antibodies must be continued life long.

Other reactions uncommonly seen and thought to be of uncertain etiology are sudden development of hypertension, convulsions, cerebral hemorrhage, and edema after multiple transfusions.

Transfusion transmitted diseases like malaria, syphilis, hepatitis B, Hepatitis C, Cytomegalovirus, and HIV infection can occur. All thalassemias who are negative for the hepatitis B surface antigen and antibody should receive hepatitis b vaccine -4 doses at day 0, 1 month, 2nd month, and 12th month intramuscularly. It also can be given intradermally in the dose of 0.1 ccs, thus reducing the cost. This has been found to be effective by some workers. However, efficacy is not well-proven.

Iron Overload and Chelation Therapy

Two factors contribute to iron overload in a thalassemic child:

• Enhanced gastrointestinal absorption of iron.

• Transfusional siderosis

Normal body iron content is 3-5 gm, whereas in a thalassemic child it could be around 0.75 gm/kg. It results from increased GI absorption of iron and blood received during transfusion therapy. In normal individual 1 mg of iron/day is absorbed from the gut, while in a thalassemic child it may be as high as 10 mg/day. Each cubic centimeter of packed cells contains 1-1.6 mg of iron. With an average annual transfusion requirement of 180 cc/kg of packed cells, the body accumulates 200 mg/kg of iron every year. Transfusional iron overload leads to deposition of iron in the heart leading to cardiomyopathy and irregularity of heartbeats, in the pancreas, in the Islet of Langerhans leading to diabetes, in the liver and spleen leading to hepatosplenomegaly, hepatic fibrosis and cirrhosis of the liver, in the pituitary glands leading to growth retardation, delayed puberty character, in the thyroid and parathyroid gland leading to that subclinical or clinical organ dysfunction, and in the skin leading to bronze or black discoloration of the skin. Increased susceptibility to bacterial infection especially Yersinia is seen with iron overload, because relatively high serum iron levels may favor bacterial growth, or because of blockage of the mononuclear phagocyte system by the excessive red cell destruction. Iron accumulation in the myocardium can lead to death, either by involving the conducting tissues or by causing intractable cardiac failure due to cardiomyopathy. Serum ferritin concentration reflects the iron overload and is usually above 1000 ug/L. S. Ferritin above 7500 ug/L is found to be lethal. Despite extensive research for an ideal chelating agent, desferrioxamine is currently the only chelating agent of real value for the management of thalassemia, being able to promote the excretion of iron.

DESFERRIOXAMINE (DFO):

Desferrioxamine is a hydroxylamine compound produced by streptomyces pilots. A single gram of DFO is able to bind 85 mg of iron. Desferal (Desferrioxamine) should be started before the age of 3-5 years. Given on daily basis for a minimum of 5-6 times per week, it is given subcutaneously over 6-8 hours using an infusion pump. The daily dose of Desferal is about 30-70 mg/kg and should be tailored according to the need of the patient. In general, the goal is to keep the serum ferritin level below 1000 ng/ml.

TOXICITY OF DESFERAL:

Toxicity is minimal, no tachyphylaxis has been observed. When given parenterally there may be the liberation of histamine leading to bradycardia, hypo/hypertension, rigors, headache, photophobia, feeling cold and hot, etc. When given subcutaneously, local pain, induration, irritability, and redness may occur. The visual abnormality may occur and includes decreased acuity of vision, peripheral field vision defects, defective dark adaptation, thinning of retinal vessels, retinal stippling and abnormal visual evoked responses and cataract, in 4-10% of patients.

High incidence of high-frequency sensorineural hearing loss has been reported in 4-38% of patients. As the auditory and visual toxicity are reversible, yearly slit-lamp examination and audiometry are mandatory. Delayed linear growth has also been reported in children under three years of age treated with Desferal and may be accompanied by mild skeletal abnormalities such as the short trunk, sternal protrusion, and genu valgum.

ROLE OF VITAMIN C:

Ascorbic acid deficiency increases insoluble iron (hemosiderin). Vitamin C helps in the conversion of hemosiderin into ferritin from which iron can be chelated. High doses of Vitamin C can lead to increased free radical reaction and lipid peroxidation resulting in tissue damage and rapid cardiac decompensation and even death. The addition of vitamin C 100 mg daily prior to DFO therapy increases iron excretion. 60% of DFO chelated iron is excreted in urine and 40% in the stool.

NEWER CHELATING AGENTS:

Over the last 20 years, more than 500 oral chelating compounds have been tried all over the world in search of an ideal chelating agent that can be effective, cheap, safe, and can be given orally.

Among the various drugs under trial, few have completed animal studies, a few are being tried in human volunteers. The only drug which has entered human trial is Dimethylhydroxy Pyridone (1,2 Diemethy1-3-Hydroxy Pyrid-4-one (L1), developed in Hider's laboratory-London⁴⁰, also called as Deferiprone and is available in India with the brand name of Kelfer.

Deferiprone (L1):

Absolute neutropenia and thrombocytopenia also have been reported in occasional cases. Physical examination, particularly of the joints and complete blood count including platelet count, must be done regularly when child is on Deferiprone (L1) therapy.

Splenectomy

With the advent of hyper and super-transfusion therapy, splenomegaly and hypersplenism have become a rarity and hence splenectomy is usually not needed in these patients. If the child has already developed splenomegaly and signs of hypersplenism and is above 5 years of age, splenectomy is indicated. The indications for splenectomy are:

• An increase in the yearly requirement of packed cells more than double the basal requirement i.e. packed cell 200 cc/kg/year or more.

• Decrease in WBC and platelet count, which is a late manifestation of hypersplenism.

• All children needing splenectomy should receive the pneumococcal vaccine

• H-influenza vaccine, and meningococcal vaccine 4 weeks prior to surgery.

• In endemic areas, prophylactic antimalarial treatment may be given to prevent malaria.

• Prophylactic penicillin therapy must be continued life-long.

• Episodes of infection should be treated promptly and newer antibiotics may be empirically started to prevent septicemia and other complications (if necessary these children should be hospitalized). Blood culture and sensitivity of antibiotics must be performed to guide treatment.

Bone Marrow Transplantation

A ray of hope for a permanent cure and a better future for children with genetic disorders has brightened with the rapid advancement in the techniques and the success of bone marrow transplantation. The credit of first bone marrow transplantation in thalassemia major goes to E.Donald Thomas who performed this procedure in an 18-month-old thalassemic child in 1982 using HLA matched elder sister as a donor. This child was cured of thalassemia. The first BMT in thalassemia in India was successfully done by Dr.M.Chandi at Christian Medical College, Vellore.

The principles of bone marrow transplantation in thalassemia are:

• To destroy and prevent regeneration of defective stem cells

• Sufficient immune suppression for good engraftment of normal marrow

• To infuse stem cells with normal gene for beta globin.

• To prevent GVHD with high doses therapy of Busulphan, Cyclophosphamide, total body irradiation and other modalities.

All over the world, over 1000 transplantations have been done with a 70-80% cure rate.

The three most important adverse prognostic factors for survival and event-free survival are the presence of hepatomegaly (liver more than 2 cms. below costal margin), portal fibrosis, and iron overload. (Lucarelli et al). Bone marrow transplantation is most successful in patients who are young, properly transfused, well-chelated and in good clinical shape without hepatomegaly.

The cost of BMT in India is around Rs.4-5 lacs and is being done at Christian Medical College, Vellore and Tata Memorial Hospital, Parel, Mumbai, and AIIMS in Delhi.

Neocyte Transfusion

Propper et al in 1980, introduced the concept of transfusing thalassemic children with young red cells (Neocytes). In the conventionally used unit of blood, red cells have a survival of 60 days. The mean age of neophytes being 120 days, they survive in the recipient for 90 days, thus reducing the amount of blood required and prolonging the interval between two transfusions. IBM-2991 can be utilized for both washing the red cells and dividing them into populations of different ages by differential centrifugation techniques. There is a reduction in the total units of blood transfused and iron overload. However, this is not cost-effective. The requirement of blood donors is increased and it requires costly equipment, technology, and highly developed transfusion services. It is also time-consuming.

Pharmacological MethodstTo Increase Gamma Chain Production and Gene Manipulation

The main pathology of beta-thalassemia is reduced production of beta-chain leading to an excess of the unpaired alpha-globin chain which precipitates leading to ineffective erythropoiesis or hemolysis of RBCs resulting in anemia. It has been noted that hypomethylation of a gene increases its expression and when methylated, the gene is not expressed. A number of drugs like 5'Azacytidine and hydroxyurea have been shown to increase the production of gamma chains both in animals and human beings by causing hypomethylation of genes by decreasing the activity of the enzyme DNA methyltransferase. This increase in gamma chain synthesis prevents the Alpha chain precipitation by forming HbF (a 2 g 2) and thereby increasing the life span of red cells. 5-Azacytidine is recommended in the dose of 2 mg/kg/day intravenous infusion in ringer lactate or saline solution at the rate of 6 mg/hour for 7 days. This leads to an increase in Hb from 8 to 10.8 gm% in 2-3 weeks and an increase in fetal Hb from 1.06% to 20% on the 40th day. Side effects like nausea, vomiting, suppression of bone marrow, and potential carcinogenesis have put limitations on its use in practice and unless a more effective compound with less toxicity becomes available such therapy is not recommended for thalassemia major. Augmenting the production of the gamma chain reduces the imbalance of the globin chain and increases the synthesis of HbF and thus lessening the severity of the disease. Various drugs that stimulate HbF production are 5-azacytidine, hydroxyurea, Butyrate compounds, and erythropoietin.

Butyrates:

These are found naturally increased in diabetic mothers. Their babies at birth have 100% HbF. In vitro trials found the efficacy of these drugs in increasing HbF production. This drug is given I.V. infusion slowly over 6-8 hours in a dose of 200-400 mg/kg/day and has shown to increase HbF to 8-12% and cause a rise in Hb by 2-3 gm%. The problem with this drug is the tedious I.V. route. Oral analog, Na Butyrate is useful in some patients to sustain the response after IV therapy. The side effects are few and include nausea, vomiting, electrolyte disturbances, and occasional seizures. The actual efficacy of this drug is found to be lacking in many patients with sickle cell anemia and thalassemia intermedia. Further trials are awaited before it becomes available commercially. L-carnitine, an analog of butyrate, has been tried in thalassemic patients but the response obtained has been poor in most of the trials.

Genetic Engineering:

The insertion of a normal gene in the stem cells of the recipient remains a known challenging goal of future therapy. There are two main approaches to gene therapy: 1) Somatic approach in which non-germ line cells are involved. 2) The transgenic approach in which transfused gene can be expressed in subsequent generations. This therapy is still in the experimental stage and likely to be the therapy of future management of thalassemia.

Antenatal diagnosis and genetic counseling:

As thalassemia is inherited in an autosomal recessive manner there are 25% chances of producing thalassemia major child in each pregnancy. Population screening, identification of carriers, genetic counseling, antenatal diagnosis in women at risk, and selective termination of affected fetus can prevent the birth of thalassemia major child. Prenatal diagnosis can be done by estimation of the relative rate of globin biosynthesis by fetoscopy and fetal blood sampling around 16-18 weeks of intrauterine life or by analysis of fetal DNA by ultrasound-guided chorionic villus biopsy at around 8-9 weeks of gestation or fetal amniocytes by amniocentesis.

Thalassemia Management - Conclusion

With a better understanding of molecular biology and pathophysiology of thalassemia, advances in transfusion therapy, organized quality care, and effective chelation therapy, thalassemias can become fully active members of the society with proper physical, mental and sexual growth (without any disfiguration). They are able to profit from their opportunities and enjoy positions that they are entitled to in society. With the free availability of oral chelators in the near future, and the establishment of more and more outdoor transfusion centers and thalassemia societies, the management of thalassemia major will become easier and economically feasible. With the advent of BMT, a cure is possible. Gene therapy still remains a hope for the future. In developed countries where all these facilities are already available, more and more thalassemic children are leading a normal healthy life and even achieving parenthood. Prenatal screening and diagnosis as well as modern management of thalassemia are technologically complex and expensive, and thus their benefits remain limited only to the industrialized developed world & in certain centres in India. Unfortunately, developing countries like ours still have a long way to go.