Summary Reduced bone mineral density (BMD) in childhood is a risk factor for osteoporosis in later life. This case–control study determined the prevalence of low BMD, calcium intake and physical activity in 62 haemophilic children and 62 sex‐, race‐ and age‐matched healthy boys as controls. Lumbar spine (L2‐L4) BMD was determined by dual‐energy X‐ray absorptiometry; BMD was considered to be low when Z‐score ≥2. Physical activity was assessed using a validated questionnaire and calcium intake with a standardized quantitative food frequency questionnaire. Twenty‐four patients (38%) had low BMD, whereas this was found in only 10 (16%) controls [odds ratio (OR) 2·86, 95% confidence interval (CI) 1·17–7·41; P = 0·014]. Lumbar BMD was significantly lower in the haemophilia patients than the controls (−1·6 ± 1·0 vs. −0·9 ± 0·9 respectively; P = 0·0004). Sedentary and low‐grade exercise predominated in haemophilia (77%) versus control (50%) (OR 3·2, 95% CI 1·36–7·79; P = 0·003). There were no differences between groups with regard to calcium intake. Our results suggest that low‐physical activity is a risk factor for reduced lumbar bone mass in the haemophilic group. This factor must be monitored to avoid a significant reduction in BMD that might contribute to further skeletal fragility.

Hemophilia A (HA) is one of the most common inherited bleeding disorders caused by FVIII gene mutations. Inversion of intron 22 (inv22) originates 50% of cases of severe HA and is a major risk factor for inhibitor development. Inversion of intron 1 (inv1) has been reported to occur in 2-3% of severe HA patients. We studied both inversions to determine their frequencies in Mexican patients with severe HA and to compare these data with other HA populations. The inv22 was evaluated as a risk factor for FVIII inhibitor development in severe HA patients. We studied 44 patients from 31 severe HA families for the detection of inv22 and 94 patients from 65 families to detect inv1. We used the subcycling long-distance PCR to detect inv22 and rapid PCR in duplex reactions to detect inv1. We found a frequency of 45% for the inv22 and no inv1-positive patients (0%). These frequencies were not statistically different from other populations, although haplotype analyses of FVIII gene and telomeric regions should be incorporated to explore population-specific variation of inv1 frequencies. Inv22-positive patients showed 1.88X higher risk for developing inhibitors with respect to patients carrying other severe mutations; however, this OR value was not significant. Our findings confirm inv22 as a hot-spot for severe HA and evidence the low frequency of inv1 in a Mexican population. The non-significant risk for developing inhibitors among inv22-positive patients agrees with the variety of genetic and non-genetic factors involved in such a complication. Am. J. Hematol. 82:283-287, 2007. V V C 2007 Wiley-Liss, Inc.

In Mexico, 15% of haemophilia A (HA) patients develop inhibitory alloantibodies in response to replacement therapy with factor VIII (FVIII), requiring bypass therapy such as activated prothrombin complex concentrate (APCC). Because bypass therapy has not been broadly available in Mexico even in recent years, this study aimed to evaluate the thrombin generation assay (TGA) in assessing the response to FVIII or APCC treatment in patients with severe HA positive to inhibitors. We studied 189 patients with severe HA. Clinical severity was verified by one-stage APTT-based clotting assay. Inhibitors to FVIII were investigated by the Nijmegen-Bethesda (N-B) method, and type of inhibition was assessed through serial plasma dilutions. Thrombin generation was measured with the calibrated automated thrombogram in inhibitor-positive plasmas previously spiked and incubated with FVIII or APCC. Data were analysed using anova, Student or Fisher's exact tests. We detected 47 (24.9%) subjects with high-titre (5-1700 N-B U mL(-1)) and 25 (13.2%) subjects with low-titre inhibitor antibodies (0.6-4.7 N-B U mL(-1)). We found an association between kinetic behaviour and clinical response to FVIII (P = 0.0049) or vs. FVIII response evaluated with TGA (P = 0.0007). Global concordance between clinical and in vitro response was 70%. By evaluating the capacity of thrombin formation in a plasma sample, TGA predicts the response to FVIII or APCC therapy and allows individual optimization of resources in patients with severe HA and high-titre inhibitors. The inhibition pattern of the antibodies to FVIII:C correlated with the TGA parameters and showed an association with the clinical response to FVIII.

A semi-quantitative expression analysis of both AML1-a and AML1-total was performed by RT-PCR in 19 children with acute lymphoblastic leukemia (ALL) at diagnosis. AML1-a expression was assessed in 16 bone marrow (BM) and 13 peripheral blood (PB) samples whereas AML1-total was assessed in 17 BM and 16 PB samples. These analyses were also carried out in 15 PB samples of healthy controls. In addition, 18/19 patients were karyotyped: 11 had an unmodified constitutional karyotype (CK) and seven exhibited acquired chromosomal abnormalities (ACA). The expression of AML1-a was significantly increased in BM and PB when compared with the controls (p < 0.013 and p < 0.035, respectively). A significant increase was found in the expression of AML1-a in BM of the ACA group compared with the CK group (p < 0.0009). The expression of AML1-a in BM and PB showed a significant increase in the ACA group compared with controls (p < 0.00001 and p < 0.012, respectively); in contrast, the CK group did not differ from the controls. These observations may mean that the increase of AML1-a favours the progression of leukemia.

Severe hemophilia A (HA) patients develop inhibitory alloantibodies to factor VIII:C and therefore require bypass agents that are scarce, expensive and may provoke secondary effects. Twenty-three severe HA patients who were high-responders to FVIII inhibitors were studied. FVIII:C activity in plasma was measured by one-stage activated partial thromboplastin time method, and the quantification of FVIII:C inhibitors was carried out by the Nijmegen-Bethesda method. Inhibition kinetics was assessed through serial plasma dilutions. FVIII:C activity was <1% in all patients. Kinetics behavior of the inhibitors was classified as type I in 14 patients, type II in four and an intermediate pattern that we named type III in one case. We were unable to apply the regression model to the remaining four of 23 patients in the study because of their low inhibitory titer (<3 Nijmegen-Bethesda units per ml). Seventy-eight percent of the patients with inhibitor type I did not respond to high doses of FVIII therapy, whereas 50% of patients with type II kinetics did (P = 0.5323). Generally, patients belonging to the same family had similar kinetics behavior as well as concordant treatment response. Although nonsignificant, our results suggest an association between kinetics behavior and treatment response that may be a valuable prognostic parameter for the management of these patients.