INTRODUCTION

The thalassaemias are the commonest single gene disorder in Malaysia. However studies on the molecular basis of the disease have only been done in the last 15 years, where studies have largely concentrated in populations in West Malaysia. Prenatal diagnosis for the disease have only been available on a routine basis since 1994.

I. Total population

Malaysia is a multi-racial society. The three main races are the Malays, Chinese and Indians. In addition to these there are the Ceylonese, Indonesians, Pakistanis, Europeans, Eurasians, and Thais. The Malays are the indigenous inhabitants, although some are fairly recent immigrants from Indonesia. The Overseas Chinese in West Malaysia are almost exclusively from the Southeastern provinces of China-Guandong, Fugian and Giangxi. The following figures were available for the year 1992.

II. Magnitude of the problem of thalassaemia in Malaysia

Thalassaemia is a public health problem among the Malays and Chinese of Malaysia where Indians form only a small percentage of those with thalassaemia. The frequency of the genes is 20% for a -thalassaemia (3-5%, a°, a", 16%), 3- 50% for Hb E, 3-4% for b -thalassaemia, and 1-4% for Hb Constant Spring(l).

These abnormal genes interact to give more than 60 syndromes. The anticipated number of newborn infants afflicted each year with transfusion dependent beta-thalassaemia would be 178. To institute a comprehensive thalassaemia control programme for thalassaemia in this country, we have been characterising the mutations present in Malaysia since 1984. These abnormal genes interact to give more than 60 syndromes of thalassaemia that varies from an asymptomatic person to a severe state with death in the first year of life.

b THALASSAEMIA

b-thalassaemia is heterogeneous genetic disease with an autosomal pattern of inheritance. The disease can be confusing for both the patients and doctors, as the picture varies so much from one patient to the next.

Clinical aspect

The b -thalassaemia syndromes are due to a decrease ( b +) or absence ( b °) of the production of b-globin chains found in the adult human haemoglobin (Hb A, a2b2 Specific genetic abnormalities causing decreased production of the b- globin chain have been found to affect every stage of process of information flow from DNA to RNA to protein. This results in imbalanced a/non a globin chain synthesis, which is the major determinant of the clinical and haematological severity. The phenotype b° is likely to be more severe clinically than the b+ phenotype. Clinically, b-thalassaemia is divided into thalassaemia major, thalassaemia intermedia and thalassaemia trait (Table 1). Individuals who inherit the combinations b+ / b° and b+ / b+ have thalassaemia of a moderate clinical severity ( b -thalassaemia intermedia). Individuals who inherit a b thalassaemia gene from each parent usually develop the clinical manifestations of thalassaemia major, a severe anaemia requiring regular blood transfusions for survival.

The clinical manifestations of the thalassaemia syndromes result from ineffective erythropoiesis and shortened red blood cell survival, which in turn are caused by unbalanced globin chain synthesis. Any genetic or acquired factor that reduces the degree of chain imbalance may thus be able to ameliorate the clinical severity. Hereditary ovalocytosis, iron and folate deficiency aggravate the clinical severity, a -thalassaemia and increased synthesis of Hb F ameliorate it.

Genetic aspect

Over 160 different b -thalassaemia mutations have been identified which give rise to the phenotype b -thalassaemia. Each ethnic group has 4-5 mutations that comprise over 90% of the mutations present. The distribution of these mutations are assigned to the main ethnic groups: Mediterranean, Asian-Indian, Chinese, and Malay-Melanesian. Systematic studies of patients with thalassaemia show that over 14 b -thalassaemia alleles result in thalassaemia(2-5). The interactions of these various mutations result in the heterogeneity of the thalassaemia syndromes at phenotype level.
b -thalassaemia is rarely caused by extensive deletions. Non-deletional forms generally involve single base substitutions which result in (a) defective promoters, (b) nonsence mutations, (c) splice alterations, (d) creation of a new splice signal in intervening sequences, (e) enhanced activity of cryptic splice sites in exons, (f) frameshift mutations, or (g) changes of the poly A adenylation signal (Table 2).

In Malaysia, the predominant type of beta-thalassaemia has a b phenotype. In contrast, in the Chinese-Malaysians this was found to be b°, a feature in keeping with similar findings of b-thalassaemia in south China (5), Five mutations in the Malays, and four in the Chinese comprised 94% of the mutations seen (Table 3).

The b+ transcriptional mutations -28 (A to G), -88(Cto T) and the mutations causing a polyadenylation defect, poly A (AATAA to AATAGA) are mild mutations . The mutation within the conserved promoter regions -28 (A to G) is resposible for the b-thalassaemia phenotype due to reduced b-globin mRNA production. The mutation in the second intervening sequence, IVS2-654 ( C to T) is of moderate severity and in the homozygous state has the phenotype of thalassaemia intermedia. The following b mutations in codon 17(A to T), codon 35 (-C), IVS 1-1(G to T), codon 41-42 (-TCTT), and codon 71-72(+A) are severe mutations associated with no Hb A synthesis. Patients with these mutations in the homozygous state are associated with severe anaemia and require regular blood transfusions. The most common b-thalassaemia mutation seen in the Chinese is in codon 41-42 (-TCTT) which has a b phenotype. In this latter mutation, no functional mRNA is synthesized. IVS 1-5 (G to C ) which has a b+ phenotype is the most common mutation among the Malays (6). In this mutation, Hb A is synthesized in small amounts and hence this latter mutation is clinically moderately severe. Hb E and Hb Malay are common b- thalassaemia haemoglobinopathies in Malaysia. Both have a clinical phenotype of b+ thalassaemia. Hence, the compound heterozygote of these haemoglobinopathies with a b-thalassaemia mutation will result in thalassaemia intermedia where the clinical phenotype will depend on the severity of the interacting b-thalassaemia mutation and presence of ameliorating or aggravating factors(6-8). In the Malays, this interaction in the majority results in thalassaemia intermedia which is not blood transfusion dependent. DNA studies form an essential part in the characterization of the b-thalassaemia phenotype. This provides the information on the prognosis of the disease, aids the planning of treatment protocols, genetic counselling, and prenatal diagnosis. However the expertise for this is limited in Malaysia, DNA diagnostic tests being available in 3 centres, 2 in the Klang Valley (Hospital Universiti Kebangsaan Malysia, University Hospital) and the third in the north at Universiti Sains Malaysia in Kelantan. Prenatal diagnosis is being offered at the centres in the Klang Valley.

II. Health Budget

There is no budget allocated solely for the management of thalassaemia patients.

III. Desferal iron chelation therapy

A limited number of patients are provided with iron chelation therapy. This was commenced in 1978 for a few patients and no newly diagnosed children have been allowed Desferal (Desferroxamine B methane) therapy from government funding after 1986. In 1998, because of the reduction of allocation of funds for drug purchase, Desferal (DF) has been placed as 'non formulary drug' and no stocks are available through government fUnding. Patients have to buy Desferal for use either at hospital price or at the pharmacy.

Desferal as purchased from Novartis Corporation (Malaysia) Sdn Bhd Company 1
No. 10920-H, Lot 9 Jalan 26/1, Kaw Perindustrian Hicom, 40400 Shah Alam.
Tel 603-5116500, Fax 603-5116514
Total number of boxes sold by Novartis: 10 vials per box

From a local study done by Dr. Pyar Kaur, Senior consultant Paediatrician, Hospital Pulau Pinang, the number of transfusion dependent thalassaemia patients was identified as 942 in 1996. In retrospect, a single patient on DF on the average of I vial/per day/ would need to use about 365 vials a year i.e. 36.5 boxes (10 vials per box). For 942 patients this would lead to the use of 34,383 boxes or 343.830 vials of DF. In 1996. Novartis recorded the sales for DF in Malaysia as 7,938 boxes. Thus only 217 (23.0%) of patients received DF (if one assumes that all the DF sold by Novartis was used by thalassaemia patients. 725 (77%) of transfusion dependent thalassaemics are destined to die in the 1st or 2nd decade of life in the absence of iron chelation therapy(9-10).

IV. BLOOD TRANSFUSIONS

The following are guidelines for the rational use of blood products in transfusion dependent thalassaemia patients from a consensus study coordinated by the National Blood Services Centre Kuala Lumpur.
(a) the blood group phenotype should be done at the time of diagnosis
(b) screen for HbsAg and immunise if not already done at birth
(c) transfUse packed red .cells to maintain the Hb at 120 G/L for hyper-transfusion regime where patients are given desferal for chelation therapy.
* if chelation is not available, a low or intermediate transfusion regime may be followed.
The red cells used for transfusion should be preferably be white cell depleted. Use filters for filtering packed red cells is recommended. The packed red cells used for thalassaemia should be less than 12 weeks old. Pre and post transfusion Hbs (1-24 hrs after transfUsion) should be recorded. Hbs should be monitored to achieve at least a 20-30 G/Lrise in haemoglobim. The Hb levels, amounts and dates of transfusions should be recorded to look for a change in pattern in transfusion requirements.

The above serve only as guidelines, and physicians managing the transfusion requirements of thalassaemia patients practise regimes of their choice. In Malaysia, the current practice at the National Blood Services Centre is to provide buffy coat poor packed cells to all patients and filtered blood on request to those patients with a past history of transfusion reactions. Prestorage filteration is not practised. Bedside filters may be purchased by patients at a price from RM 60-200 for use during transfusions and these are provided free at government hospitals depending upon their availability. Most transfusion dependent beta-thalassaemia patients are on low-moderate transfusion programs. Pretransfusion Hbs are 60-70 G/L and post transfusion Hbs at 100- 110 G/L. Only a few are on hypertransfusion programs. Blood banks in Malaysia screen blood for HIV, HBV and HCV. HBV immunisation is provided to all patients with thalassaemia since 1992.

V. PRENATAL DIAGNOSIS

Facilties for DNA based studies on fetal DNA obtained from fetal blood and chorionic villus samples for prenatal diagnosis of thalassaemia are currently available at the University Hospital and Hospital Universiti Kebangsaan Malaysia. Obstetricians trained in chorionic villus sampling are limited in number.

VI. BONE MARROW TRANSPLANTATION

These facilties are available at University Hospital Kuala Lumpur and at Hospital Kuala Lumpur.

VII THALASSAEMIA ASSOCIATIONS

(1) Malaysian Association ol Thalassaemia
c/o Mr. Abd Gani bin Che Man
105-2 Jalan Kg Pandan, Tamar
Maluri, 55100 Kuala Lumpur.
Tel- 03-9857688

(2) Penang Thalassaemia Society
56 Jalan Goh Guan Ho
11400 Penang
Tel: 04-2288048

(3) Kedah Thalassaemia Society
5017 (1st Floor) Taman PKNK
05200 Alor Setar, Kedah.
Tel: 04-7307140

(4) Johor Thalassaemia Society
Lot 5395 Jalan Kurniawati, Kampung
Kurnia, 80250 Johor Bharu
Tel: 07-3320369

(5) Sarawak Thalassaemia Society
c/o Dr. Bibiana Teo's clinic
Jalan Keretapi, 93150 Kuching,
Sarawak
Tel: 082-420008

(6) Perak Thalassaemia Society
190 Persiaran Bercham Selatan 26
Taman Sri Kurau, 31400 Bercham,
lpoh, Perak.
Tel: 05-5468476

(7) Kuantan Thalassaemia Society
c/o Wong Cheng Wah
48, 2nd Floor Jalan Gambul
25000 Kuantan, Pahang.
Tel: 010-9877131

(8) Sabah Thalassaemia Society
c/o Pathology Dept.
Hospital Queen Elizabeth
88586 Kota Kinabalu, Sabal-
Tel: 088-218766

**AII seven thalassaemia societies function independantly from the Malaysian Association of Thalassaemia. The 'Malaysian Association of Thalassaemia' 'appears' to involve only the Klang Valley i.e. around Kuala Lumpur.

References
1. George E, Khuziah R. Malays with thalassaemia in west Malaysia.
Trop. Geogr. Med. 1984, 36: 123-125.

2. Yang KG, Kutlar F., George E et al. Molecular characterization of b-globin gene mutations in Malay patients with Hb E-b thalassaemia and
thalassaemia major. Brit. J. Haematol. 1989, 72: 73-80.

3 George E, Li HJ, Fei FH et al. Types of thalassaemia amomg patients attending a large University clinic in Kuala Lumpur, Malaysia.
Hemoglobin 1992(l&2): 51-66.

4. Jankovic L, Effrernov GD, Petkov G et al. Two novel mutations leading to b+ - thalassaemia . Brit. J. Haematol. 1990, 75: 122-126.

5. George E, Yamg KG, Kutlar F et al. Chinese in west Malaysia: the geography of beta thalassaemia mutations. Singapore Medical Journal 1990 31-374-377

6. George E, Wong HB. Hb E b- thalassaemia in west Malaysia: clinical features in the most common beta-thalassaemia mutation of the Malays IVS 1-5 ( G to C). Singapore Medical Journal 1993, 34: 500-503.

7. George E. Hb E P-thalassaemia, a west Malaysian experience 1992.
(ISBN-983-997766-05)

8. George E, Huisman THJ, Faridah K et al. First observation of haemoglobin Malay. Med. J. Malaysia 19989, 44, 3: 256-262.

9. George E. MD thesis. A review of thalassaemia syndromes in west Malaysia and an evaluation of the serum ferritin levels in this condition. National University of Singapore 1992.

10. George E. Wong HB, George R et al. Serum ferritin concentrations in transfusion dependent beta-thalassaemia. Singapore Medical Journal 1994 35- 62-65