Polymorphism of the human platelet antigen-5 system is a risk factor for occlusive vascular complications in patients with sickle cell anemia.
BACKGROUND
Polymorphisms of platelet membrane glycoproteins such as human platelet antigen (HPA)-1b, HPA-2b, the -5T/C Kozak sequence and C807T have been described as risk factors for vascular disease. Vaso-occlusion episodes are a common feature of sickle cell anaemia (SCA), leading to complications such as stroke, acute chest syndrome, avascular head femur necrosis and priapism. Complex interactions are involved in vaso-occlusion, and activated platelets may play an important role. These data raised the question of whether platelet polymorphisms could be implicated in occlusive vascular complications (OVC) of SCA.


METHODS
In this study, 97 patients with SCA were analysed in two groups: 34 patients presenting with OVC (SCA-VC) and 63 without these complications (SCA-N). The distribution of the HPA-1, -2 and -5 systems, as well as C807T dimorphism and -5T/C Kozak sequence alleles, was evaluated using DNA-based methods.


RESULTS
Patients of the SCA-VC group showed a higher frequency of the HPA-5b allele (0.324) compared with those of the SCA-N group (0.111) (chi2 = 13.19, P = 0.0002). None of the other polymorphisms, isolated or associated as haplotypes, demonstrated any correlation with the development of OVC in these patients.


CONCLUSIONS
The findings of this study suggest that the HPA-5b allele is a genetic risk factor for the development of OVC in patients with SCA. This allele could be explored as a target for the development of new therapeutic approaches.
Castro
V
V
Hematology and Hemotherapy Center, State University of Campinas-UNICAMP, São Paulo, Brazil. vagner@unicamp.br
Alberto
F L
FL
Costa
R N P
RN
Lepikson-Neto
J
J
Gualandro
S F M
SF
Figueiredo
M S
MS
Annichino-Bizzacchi
J M
JM
Saad
S T O
ST
Costa
F F
FF
D000293:Adolescent; D000328:Adult; D000368:Aged; D000755:Anemia, Sickle Cell / Q000150:complications*; D016824:Antigens, Human Platelet / Q000235:genetics*; D001157:Arterial Occlusive Diseases / Q000209:etiology* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D012307:Risk Factors
C055973:5b alloantigen, human; D016824:Antigens, Human Platelet