Serum calcium and vitamin D status of patients with sickle cell disease in Curacao: comparison with Saudi Arabia

Data from Saudi Arabia suggest that low vitamin D status is involved in skeletal abnormalities of patients with homozygous sickle-cell disease (HbSS). We measured parameters of calcium homeostasis and vitamin D status in HbSS patients (median age: 8 years, range: 3-19; 8 females, 10 males) and matched HbAA controls living in the tropical island of Curacao. Serum calcium of HbSS patients (2.32 ñ 0.07 mmol/l) was lower (ANCOVA, p = 0.002) than that of HbAA controls (2.44 ñ 0.14). None of the subjects had hypocalcaemia. There were no differences in phosphate, total protein, albumin, intact parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D; HbSS 87 ñ 27, HbAA 86 ñ 15 nmol/l] and 1,25-dihydroxyvitamin D. There were no significant relationships between serum calcium and albumin, calcium and total protein, and PTH and 25 (OH)D. Our data suggest that hypocalcaemia and hyperparathyroidic tendencies in Saudi Arabian HbSS patients are likely to be caused by the locally poor vitamin D status, attributable to insufficient exposure to direct sunlight (AU)

Two different forms of homozygous sickle-cell disease - abstract

Haematological, clinical and some molecular genetic features have been compared in two groups of patients with homozygous sickle-cell (SS) disease in Saudi Arabia, 33 patients from the Eastern Province (eastern) and 30 from the South Western Province (Western). Eastern patients all had the Asian haplotype of DNA polymorphisms within the beta globin gene cluster whereas Western patients were more variable but predominantly of the Benin haplotype. Eastern patients had significantly more deletional alpha thalassaemia, higher levels of total haemoglobin and foetal haemoglobin, and lower of HBA, mean volume reticulocytes, and platelets. Clinically, Eastern patients had a greater persistence of splenomegaly, less dactylitis, less acute chest syndrome, a more normal body build and greater subscapular skin fold thickness. Painful crises occurred with equal frequency in both groups. Avascular necrosis of the femoral head was common in both groups. The disease in the Eastern province has many mild features consistent with the higher HbF levels and more frequent alpha thalassaemia but bone pathology (painful crises, avascular necrosis of the femoral head, osteomyelitis) remains common. The disease in the West is more severe, consistent with the Benin haplotype suggesting an African origin (AU)

A genetic marker for elevated levels of haemoglobin F in homozygous sickle cell disease

Ten patients with sickle cell (SS) disease from a Jamaican family were found to have unusually high levels of haemoglobin F for this population. Each of them has inherited one sickle cell gene on a chromosome characterized by an arrangement of restriction fragment length polymorphisms (haplotype) which is very rare in the Jamaican population. Genetic analysis of the family suggests that there is a determinant linked to the á-globin gene cluster, charaterized by this haplotype, which is responsible for increased haemoglobin F production in response to anaemia. Interestingly this particular haplotype appears to be common in patients with SS disease in eastern Saudi Arabia in whom a high level of haemoglobin F is the rule rather than the exception. Hence it is possible that this haplotype (++-++) acts as a genetic marker for elevated levels of haemoglobin F in sickle cell disease (AU)

Neonatal screening for sickle cell disease in the Eastern Province of Saudi Arabia

Neonatal screening for sickle cell disease has been established in three hospitals in the Eastern Province of Saudi Arabia. In the first 17 months of this programme, 5630 cord blood samples were screened with the detection of 47 babies with an FS phenotype. The sickle cell trait occurred in 4.4 percent births at Al Khobar, in 6.7 percent in Dammam and in 17.9 percent in Qatif. An apparent excess of the FS phenotype over that predicted from the observed S gene frequency occurred at all three centres. The cause of this excess remains unknown although a high prevalence of sickle cell-beta-o thalassaemia and the effects of non-random mating may be contributory factors. (Summary)

Hb F synthesis in sickle cell anaemia: a comparison of Saudi Arab cases with those of African origin

Fetal haemoglobin (Hb F) synthesis has been studied in 22 cases of sickle cell anaemia (SS) from Saudi Arabia and compared with an equal number of cases of African origin. Among the Saudi Arabs y chain synthesis ranged from 4.0 percent to 19.9 percent of the total non-x chain synthesis (mean 8.1 percent) while the corresponding range for the Negro cases was <0.3 percent to 4.6 percent (mean 1.7 percent). In both groups the peripheral blood HB F level was on average 3-4 times higher than the proportion synthesized, indicating that the selective survival of Hb F containing cells (F cells) was an important factor in determining the final Hb F levels. Among the Saudi Arab cases there was a significant negative correlation between the degree of F cell enrichment and either the Hb F level or the percentage y chain synthesis. No such correlation was observed among the Negro cases. A high proportion of the cases in both groups were carriers of x thalassaemia in addition to SS, but no effect of x talassaemia on Hb F production was observed (AU)