Hemolytic disease of newborn (HDN) due to blood group incompatibility is the cause of hyperbilirubinemia in a large number of neonates(1). With the decline in Rh(D) HDN due to anti-Q immunoprophylaxis, HDN due tc:> antibodies to other blood group antigens such as non (D) rhesus (C, c, E, e, C e(f), C^x, E^W, Rh 36, Rh 37), Kell (K, Js^a JS^b), Duffy (Fy^b) Kidd Jk^a, Jk^b, JK3), MNS (M, S, s, U), Diego (Di^a, Di^b) and P Blood group systems have become a relatively greater problem(2). Heddle et al.(3) found that the most frequently produced red cell alloantibodies were to the antigens of Rhesus, Kell and Kidd system. We report a case of HDN due to the presence of anti-Jk^b antibodies in the mother.

A 28-year-old fourth-gravida mother delivered a full term appropriate-for-gestation female baby. The birth weight was 2.7 kg and the apgar score was 7, 8, 8 at 1, 5 and 15 minutes, respectively. The baby was noticed to be icteric at 30 hours of age. There was no history of neonatal hyper- bilirubinemia in any of the siblings. The mother had no history of antepartum hemorrhage, abortion or intrauterine death in earlier pregnancies. She had a history of blood transfusion fifteen years back. On physical examination of the neonate, no significant finding was observed. The investigation revealed a total serum bilirubin of 14.4 mg/dl, with a predominance of unconjugated bilirubin (13. 8 mg/dl). The blood group was B Rh(D) positive and di- rect antiglobulin test was negative. Hemoglobin concentration was found to be 18.8 g/dl with a reticulocyte count of 6%. Peripheral blood smear showed polychro-matophilia with nucleated red cells (10/100 WBC). The blood glucose level was 90 gl dl. G6PD screening done by methylene blue reduction test showed normal activity. Septic screen did not reveal any abnormality.

Blood group of the mother was 0 Rh (D) positive. A partial Witebsky test was done to look for evidence of ABO-HDN by performing IgG anti-A and IgG anti-B titres. IgG titres of more than 1:32 were considered significant. The titres of IgG anti-A and IgG anti-B were low (1:2 and 1:4, respectively). Maternal serum was , tested against screening red cells consisting of two OR₁R₁ and one OR₂R₂ red cells carrying most of the clinically significant blood group antigens in the homozygous state. The techniques used for antibody screening were saline at 22.C (room temperature), saline at 37°C, albumin layering, enzyme (pa- pain-cystein) and indirect antiglobulin test (IA T). An antibody was detected with en- zyme technique against one of the screening cells. The antibody Was identified using a red cell panel of 10 'O' cells fully typed for antigens of clinical importance. The antibody was identified as, anti-Jk^b. The baby responded to phototherapy.

Antibodies in Kidd system are generally IgG with potential to cross placenta and these show dosage effect. There are three known antibodies to Kidd antigens, i.e., anti-Jk^a, anti-Jk^b and .anti-Jk3 (anti-Jk^a-b-)(4). Anti-Jk^a is the most commonly encountered of these. Both anti-Jk^a and anti-Jk^b can cause HDN and severe hemolytic transfusion reaction. Anti Jk-3 has been known to cause mild HDN. These antibodies have a propensity to disappear rapidly from the patient's sera. In a study(S), 10 out of 17 anti-Jk^a and 4 out of 11 anti-Jk^b which were detected during initial testing disappeared on long term follow up. Anti-Jk^b has been frequently detected in association with other antibodies such as anti-S, anti-Fy^a, anti-C, anti-M and other kidd antibodies(6). Forty one per cent of women with anti-Jk^b had autoimmune disease in a series(6).

This case emphasises the importance of antibody screening in sera of mothers of hyperbilirubinemic neonates. Anti-Jkb is a clinically significant antibody which may be associated with significant risk of HDN and 1 or stillbirth in subsequent pregnancies and, therefore a close monitoring of future pregnancies by clinical, laboratory and radiologic investigation is required. As the baby has persistent maternal antibodies for ,a period of first four months, the red cell transfusions 1 exchange transfusion during this period should be Jk^b negative. Ex-change transfusion using Jk^b positive red cells will worsen the jaundice by causing increased hemolysis.

We would also like to highlight that blood transfusion department should develop red cell panel for antiqody screening. The preparation of red cell panel is cost effective as once prepared and properly frozen at -80⁰ C, these can be used for all future investigation for maternal antibody screening for a period of more than 10 years. Maternal antibody screening of hyperbilirubinemic neonates may therefore not only help in diagnosis of the case but also assist in the management of the case and future pregnancies.

 

V. Tomar,
N.Dhingra,
N. Madan,
M.M.A. Faridi*,
Departments of Pathology and Pediatrics*,
University College of Medical Sciences
and G. T.B. Hospital,
Delhi 110 095,
India.