Stroke may appear to be rare in Saudi‐Arabian and Nigerian children with sickle cell disease, but not in Cameroonian sickle cell patients

Abstract

We read with much interest the excellent review entitled ‘Defining stroke risk in children with sickle cell anaemia’ (Hoppe, 2005), but felt the necessity to clarify two issues. In reviewing the epidemiology of stroke in sickle cell disease (SCD), Dr Hoppe stated that, ‘Stroke appears to be rare in SaudiArabian and Nigerian children with SCD’ and cited among other studies Izuora et al (1989) and Obama et al (1994). Concerning the incidence rates of stroke in SCD in Nigeria, Izuora et al (1989) did report a relative incidence of associated neurological disorders of 1AE3% and that cerebrovascular accidents were responsible for 57AE5% of that number. It should be noted that the study by Obama et al (1994) was not done in Nigeria. This study was done in Yaounde, Cameroon: a neighbouring country to Nigeria. In this study of paediatric stroke in general, the average annual stroke incidence was 1AE85 per 1000 (18AE5%) paediatric hospitalisations in Yaounde and the main aetiological factor was homozygous SCD, accounting for nearly a third of stroke cases (31AE4%). We have recently studied a sample of 120 homozygous sickle cell patients in Yaounde, Cameroon. Clinical examinations and computerised tomography scans identified a stroke prevalence of 6AE7% with an annual recurrence rate of 25% (Njamnshi et al, 2005). This prevalence rate in our study might be an underestimation, given that we did not use more sensitive procedures that detect silent infarcts like magnetic resonance imaging and neuropsychological testing. Moreover, recent genetic studies indicated that the Cameroon and atypical haplotypes were more prevalent than reported in patients with homozygous (SS) sickle cell disease in general (Sarnaik & Ballas, 2001). In one report on 80 beta S chromosomes studied in Cameroonians, 13 exhibited the Cameroon haplotype (Lapoumeroulie et al, 1992). Furthermore, neonates with four or more alpha-genes whose beta(S) haplotype was Ben/CAR, Cameroon or CAR/CAR seemed to be at a higher risk for cerebrovascular accidents than other patients (Sarnaik & Ballas, 2001; Lyra et al, 2005). This may explain why stroke does not appear to be rare in Cameroonian sickle cell patients. In conclusion, we believe that stroke is not so rare in SCD, as reported in African patients and, for Cameroon in particular, stroke risk in these patients may be even higher because of the presence of atypical beta(S) haplotypes. It is therefore important not to minimise the magnitude of this problem, which has far reaching consequences. Alfred Kongnyu Njamnshi Ambroise Wonkam Vincent de Paul Djientcheu Pierre Ongolo-Zogo Marie-Therese Obama Wali F. T. Muna Roman Sztajzel Faculty of Medicine and Biomedical Sciences, University of Yaounde 1, Yaounde, Cameroon, Africa, Department of Neurology, and Department of Genetic Medicine and Development, University Hospitals of Geneva, Geneva, Switzerland E-mail: aknjamnshi@yahoo.co.uk