Fetal hemoglobin-boosting haplotypes of BCL11A gene and HBS1L-MYB intergenic region in the prediction of clinical and hematological outcomes in a cohort of children with sickle cell anemia.

Single nucleotide polymorphisms (SNPs) of BCL11A gene and HBS1L-MYB intergenic region (named HMIP-2) affect both fetal hemoglobin (HbF) concentration and clinical outcomes in patients with sickle cell anemia (SCA). However, no previous study has examined the interaction among these SNPs in the regulation of HbF. We examined whether HbF-boosting haplotypes combining alleles of functional SNPs of BCL11A and HMIP-2 were associated with clinical outcomes and hematological parameters, and whether they interact to regulate HbF in a cohort of Brazilian children with SCA. The minor haplotype of BCL11A ("TCA", an allele combination of rs1427407, rs766432, and rs4671393) was associated with higher HbF, hemoglobin and lower reticulocytes count compared to reference haplotype "GAG". The minor haplotype of HMIP-2 ("CGC", an allele combination of rs9399137, rs4895441, and rs9494145) was associated with higher HbF and hemoglobin compared to reference haplotype "TAT". Subjects carrying minor haplotypes showed reduced rate of clinical complications compared to reference haplotypes. Non-carriers of both minor haplotypes for BCL11A and HMIP-2 showed the lowest HbF concentration. Subjects carrying only the minor haplotype of BCL11A showed significantly higher HbF concentration than non-carriers of any minor haplotype, which showed no significant difference compared to subjects carrying only the minor haplotype of HMIP-2. Interestingly, subjects carrying both minor haplotypes of BCL11A ("TCA") and HMIP-2 ("CGC") showed significantly higher HbF levels than subjects carrying only the minor haplotype of BCL11A. Our novel findings suggest that HbF-boosting haplotypes of BCL11A and HMIP-2 can predict clinical outcomes and may interact to regulate HbF in patients with SCA.

Evidence for interactions between inflammatory markers and renin-angiotensin system molecules in the occurrence of albuminuria in children with sickle cell anemia.

Sickle cell anemia (SCA) is an important cause of chronic kidney disease, but its pathophysiology is not completely understood. The aim of this study was to compare inflammatory biomarkers in urine samples of SCA children with and without albuminuria, and to explore correlations with renin-angiotensin system (RAS) molecules. A cross-sectional study of 213 children selected from the Minas Gerais state cohort were assigned to two groups: Group 1-89 children with SCA who had albuminuria; Group 2-124 children with SCA and normal albuminuria matched by age and sex with group 1. A subset of 89 children was prospectively followed for a median time of 1.1 year. Inflammatory biomarkers (chemokines and cytokines) in urine were measured using cytometric beads array, and RAS molecules were measured by ELISA. Children with albuminuria had significantly higher urinary levels of IP-10/CXCL10, MCP-1/CCL2, MIG/CXCL9, IL-8/CXCL8, IL-12p70, TNF, IL-10, and IL-6 than patients with normal albuminuria. In the correlation analysis, albumin/creatinine ratio was significantly and positively correlated with IP-10/CXCL10, MCP-1/CCL2, MIG/CXCL9, IL-8/CXCL8, TNF, IL-10, and IL-6. Significant correlations were found between inflammatory and RAS molecules. In the prospective analysis, cumulative risk of persistent albuminuria was higher for children with urinary levels of IP-10/CXCL10 or IL-6 above the 50th percentile. Our data showed that inflammatory markers and RAS molecules might contribute to the occurrence of albuminuria in children with SCA, suggesting that both pathways interact in sickle cell nephropathy.

Functional polymorphisms of BCL11A and HBS1L-MYB genes affect both fetal hemoglobin level and clinical outcomes in a cohort of children with sickle cell anemia.

Fetal hemoglobin (HbF) ameliorates clinical severity of sickle cell anemia (SCA). The major loci regulating HbF levels are HBB cluster, BCL11A, and HMIP-2 (HBS1L-MYB). However, the impact of noncoding single-nucleotide polymorphisms (SNPs) in these loci on clinical outcomes and their functional role on regulating HbF levels should be better elucidated. Therefore, we performed comprehensive association analyses of 14 noncoding SNPs in five loci with HbF levels and with clinical outcomes in a cohort of 250 children with SCA from Southeastern Brazil, and further performed functional annotation of these SNPs. We found SNPs independently associated with HbF levels: rs4671393 in BCL11A (ß-coefficient = 0.28), rs9399137 in HMIP-2A (ß-coefficient = 0.16), and rs4895441 in HMIP-2B (ß-coefficient = 0.15). Patients carrying minor (HbF-boosting) alleles for rs1427407, rs93979137, rs4895441, rs9402686, and rs9494145 showed reduced count of reticulocytes (p < 0.01), while those carrying the T allele of rs9494145 showed lower white blood cell count (p = 0.002). Carriers of the minor allele for rs9402686 showed higher peripheral saturation of oxygen (p = 0.002). Patients carrying minor alleles in BCL11A showed lower risk of transfusion incidence rate ratio (IRR ≥ 1.3; p < 0.0001). This effect was independent of HbF effect (p = 0.005). Carriers of minor alleles for rs9399137 and rs9402686 showed lower risk of acute chest syndrome (IRR > 1.3; p ≤ 0.01). Carriers of the reference allele for rs4671393 showed lower risk of infections (IRR = 1.16; p = 0.01). In conclusion, patients carrying HbF-boosting alleles of BCL11A and HMIP-2 were associated with milder clinical phenotypes. Higher HbF concentration may underlie this effect.

Immunophenotyping of the cerebrospinal fluid as a prognostic factor at diagnosis of acute lymphoblastic leukemia in children and adolescents.

This study aimed at evaluating the use of immunophenotyping (IMP) in the identification of blast cells in the cerebrospinal fluid (CSF) of children and adolescents with acute lymphoblastic leukemia (ALL). Sixty-seven patients aged 18 years or younger were included. Fifty-five CSF samples were analyzed at initial diagnosis and 17 at the time of relapse. A cytological analysis (CA) was performed in all 72 samples, while IMP was done in 63. Blasts were identified in only three samples by CA, whereas all three samples were found negative by IMP, one of which had no isolation of nucleated cells after centrifugation. Among the samples analyzed by IMP, 11 showed a positive blast count, two of which had been inconclusive using CA. No equivalence was found between CA and IMP results (p = 0.55). CSF IMP positivity was not associated with other risk factors for ALL relapse. Among the 55 patients included at the time of diagnosis of ALL, eight relapsed during follow-up. Considering the cases of central nervous system (CNS) relapse, one of the patients belonged to the CSF IMP-positive group (11%) at diagnosis, and the other two cases, to the IMP-negative (5%) group. Detection of CSF blast cells using IMP was associated with a worse overall (p < 0.0001) and event-free survival (p < 0.0001). These results show that CSF IMP may be a useful additional method to conventional CA in the diagnosis of CNS involvement in ALL, and for the identification of high-risk subgroups that would benefit from an intensified therapy.

Prevalence and incidence of erythrovirus B19 infection in children with sickle cell disease: The impact of viral infection in acute clinical events.

B19V infection is common during childhood. It is self-limited in healthy individuals, but is often associated with transient aplastic crisis in children with sickle cell disease. The aim of this study was to estimate the prevalence and incidence of B19V infection in children with sickle cell disease screened by the Newborn Screening Program of Minas Gerais, Brazil, and followed-up at Fundação Hemominas. Serum or plasma samples from 278 patients were tested for anti-B19V IgG and IgM using commercial ELISA and for viral DNA using in-house real-time PCR assays; 127 negative-children were retested about 1 year later. The median age of children at first testing was 5.9 years (0.8-12.3). The estimated prevalence of B19V was 29.5 % (95%CI 24.1-34.9 %). The incidence of B19V in those 127 negative-children was 18.2 cases/100 patient-years. All DNA-positive samples were identified as genotype 1, except one sample, in which both genotypes 1 and 3 were identified. It was observed that the higher the child's age, the higher the probability of B19V infection. The analysis of clinical and hematological data showed a significant association of B19V infection with transient aplastic crisis and acute splenic sequestration, higher frequency of transfusions, and higher rate of hospitalization, but not with acute chest syndrome or stroke. These results emphasize the impact of B19V infection on the course of sickle cell disease. Strategies to prevent and monitor B19V infection in children with sickle cell disease should be considered to diminish its morbidity in this susceptible population.

Reticulocyte count is the most important predictor of acute cerebral ischemia and high-risk transcranial Doppler in a newborn cohort of 395 children with sickle cell anemia.

Stroke is a severe clinical manifestation of sickle cell anemia (SCA). Despite the prognostic relevance of transcranial Doppler (TCD), more accurate tools to assess stroke risk in children with SCA are required. Here, we describe the effect of clinical, laboratory, and molecular features on the risk of stroke and high-risk TCD in children from the newborn cohort of Minas Gerais, Brazil. Outcomes studied were acute cerebral ischemia and high-risk TCD. Clinical and hematological data were retrieved from children's records. Genetic markers, which were known for their association with stroke risk, were genotyped by polymerase chain reaction/restriction fragment length polymorphism and sequencing. The cumulative incidence of acute cerebral ischemia by the age of 8 years was 7.4 % and that of high-risk TCD by the age of 11.5 years was 14.2 %. The final multivariate model for acute cerebral ischemia risk included high white blood cell count and reticulocyte count, acute chest syndrome rate, and the single nucleotide polymorphisms (SNPs) TEK rs489347 and TNF-α rs1800629. The model for high-risk TCD included high reticulocyte count and the SNPs TEK rs489347 and TGFBR3 rs284875. Children with risk factors should be considered for intensive risk monitoring and for intervention therapy.

The Natural History of Hb S/Hereditary Persistence of Fetal Hemoglobin in 13 Children from the State of Minas Gerais, Brazil.

Children with Hb S (HBB: c.20A > T)/hereditary persistence of fetal hemoglobin (Hb S/HPFH) have a mild clinical phenotype, but some complications have been reported. The natural history of Hb S/HPFH in children from the State of Minas Gerais, Brazil newborn cohort is described. Clinical and hematological data regarding participants' phenotypes were retrieved from medical records. The HPFH-1, HPFH-2, and HPFH-3 and α-thalassemia (α-thal) deletions were detected by gap-polymerase chain reaction (gap-PCR). Thirteen children were included, nine (69.2%) had the Hb S/HPFH-2 deletion, and four (30.8%) had Hb S/HPFH-1 deletion; 11 children (84.6%) had αα/αα, and two (15.4%) carried the αα/-α(3.7) (rightward) deletion. The mean concentration of total hemoglobin (Hb) and Hb F was 12.52 ± 0.56 g/dL and 42.31% ± 1.97%, respectively. Mild microcytosis and hypochromia were observed. We found acute clinical manifestations of sickle cell disease, such as acute chest syndrome (ACS) and acute pain crisis in four children; nine (69.2%) children were completely asymptomatic during the follow-up period. All children were classified as having low-risk transcranial Doppler (TDC). In conclusion, children with Hb S/HPFH have a mild clinical phenotype of sickle cell disease, although acute clinical manifestations may occur. High Hb F levels and absence of anemia are common hematological characteristics.

Association of alpha-thalassemia, TNF-alpha (-308G>A) and VCAM-1 (c.1238G>C) gene polymorphisms with cerebrovascular disease in a newborn cohort of 411 children with sickle cell anemia.

Cerebrovascular disease (CVD) is a severe complication associated with sickle cell anemia. Abnormal transcranial Doppler (TCD) identifies some children at high risk, but other markers would be helpful. This cohort study was aimed at evaluating the effects of genetic biomarkers on the risk of developing CVD in children from Minas Gerais, Brazil. Clinical and hematological data were retrieved from children's records. Outcomes studied were overt ischemic stroke and CVD (overt ischemic stroke, transient ischemic attack, abnormal TCD, or abnormal cerebral angiography). Out of 411 children, 386 (93.9%) had SS genotype, 23 (5.6%) had Sß(0)-thal and two had severe Sß(+)-thal (0.5%). Frequency of CVD was lower in Sß-thal group (p=0.05). No effect of VCAM-1 polymorphism on stroke or CVD risks was detected. Cumulative incidence of stroke was significantly higher for children with TNF-α A allele (p=0.02) and lower for children with HBA deletion (p=0.02). However, no association between CVD and TNF-α -308G>A was found. CVD cumulative incidence was significantly lower for children with HBA deletion (p=0.004). This study found no association between VCAM1 c.1238G>C and stroke. An association between stroke and TNF-α -308A allele has been suggested. Our results have confirmed the protective role of HBA deletion against stroke and CVD.

Clinical, laboratory, and molecular characteristics of a cohort of children with hemoglobinopathy S/beta-thalassemia.

INTRODUCTION: Hemoglobinopathy Sß-thalassemia (HbSß-thal) has a wide range of clinical and laboratory severity. There is limited information on the natural history of HbSß-thal and its modulating factors. We described the molecular, hematological, and clinical characteristics of a cohort of children with HbSß-thal and estimated its incidence in Minas Gerais, Brazil. METHODS: Laboratory and clinical data were retrieved from medical records. Molecular analysis was performed by HBB gene sequencing, PCR-RFLP, gap-PCR, and MLPA. RESULTS: Eighty-nine children were included in the study. Fourteen alleles of ß-thal mutations were identified. The incidence of HbSß-thal in the state was 1 per 22,250 newborns. The most common ßS-haplotypes were CAR and Benin. The most frequent ßthal-haplotypes were V, II, and I. Coexistence of 3.7 kb HBA1/HBA2 deletion was present in 21.3 % of children. ß-thalassemia mutations were associated with several clinical and laboratory features. In general, the incidence of clinical events per 100 patient-years was similar for children with HbSß0-thal, IVS-I-5 G>A, and IVS-I-110 G>A. Children with HbSß+-intermediate phenotypes had a more severe laboratory and clinical profile when compared with those with HbSß+-mild ones. ßS-haplotypes and α-thalassemia did not meaningfully influence the phenotype of children with HbSß-thal. CONCLUSION: The early identification of ß-thalassemia alleles may help the clinical management of these children.

Health-related quality of life among teenagers during cancer treatment in a developing country: patients' and proxies' reports.

Few studies have been performed during adolescents' cancer treatment to evaluate its interference on health-related quality of life (HRQL). The purpose of this prospective cohort study was to evaluate adolescents' HRQL during cancer treatment. The Health Utilities Index (HUI) was used for scoring. Forty-five individuals were questioned 1 month after the onset of treatment (T1) and at 4 or 6 months depending on disease type (T2). Median age was 14 years. Pain was the most frequent troublesome attribute referred to, but scores were significantly better from T1 to T2 for patients and proxies. A high correlation between patients' and family' HRQL scores was observed both at T1 and T2. Correlation of the general health scores between patients and their families was high at T1, but not so high at T2. Physicians' evaluation tended to underestimate HRQL of their patients. In conclusion, most patients and proxies reported a HRQL reduction during the initial phase of treatment, but HRQL was better later on. Generally, patient and proxy scores correlated well. Pain was the most frequently reported troublesome attribute. The patients' opinion concerning their own health and well-being should be of primary importance to assess QoL and determine therapeutic regimens.

Unstable hemoglobin Rush [beta 101(G3) Glu>Gln, HBB:c.304G>C] in a Brazilian family with moderate hemolytic anemia.

Hemoglobin Rush is an unstable variant generated by a mutation of the ß-globin gene which causes amino acid replacement Glu>Gln in the central cavity of hemoglobin (G3). Many members of a Brazilian family of Italian descent have hemoglobin Rush. This is the second report in world literature. Clinical and laboratory features were retrieved and gene mutation was characterized. Hemoglobin electrophoresis, gene sequencing, and restriction fragment length polymorphism with Hpy188I were used to characterize it. In 13 affected members, hemoglobin ranged from 9.3 to 13.0 g/dL and reticulocyte count up to 12.8%. The intensity of hemolysis appeared to be linked to increased stress. The mutation was proved to be HBB:c.304G>C, beta 101(G3) Glu>Gln. Heterozygous hemoglobin Rush should be suspected when alkaline electrophoresis shows three bands, whereas isoelectric focusing and acid electrophoresis show only two. Adequate genetic counseling to avoid intermarriage should be provided because homozygous hemoglobin Rush is predicted to be clinically severe.

Hb Stanleyville-II [α78(EF7)Asn→Lys (α2); HbA2: c.237C>A]: incidence of 1:11,500 in a newborn screening program in Brazil.

Almost 3 million babies were tested in a newborn screening program in Minas Gerais, Brazil (1998-2008); 128 who have S-like hemoglobins (Hbs) were tested for the ß(S) allele and 112 were identified through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or sequencing. Hb Stanleyville-II [α78(EF7)Asn→Lys (α2); HbA2: c.237C>A] was present in 96 children (85.7%), two in a homozygous state and 94 in a heterozygous state. Its estimated prevalence was 1:11,500. Hbs Hasharon [α47(CE5)Asp→His, GAC>CAC (α2)], Ottawa [α15(A13)Gly→Arg (GGT>CGT) (α2 or α1)], G-Ferrara [ß57(E1)Asn→Lys (AAC>AAA or AAG)], St. Luke's [α95(G2)Pro→Arg, C CG>C GG (α1)], Maputo [ß47(CD6)Asp→Tyr (GAT>TAT)] and Etobicoke [α84(F5)Ser→Arg (AG C>AG G or CGC or AGA) (α2 or α1)] were also identified. Many children with Hbs Stanleyville-II and Hasharon also co-inherited the -α(3.7) thalassemia gene. African ancestry was recognized by parents of all 31 children with Hb Stanleyville-II who were interviewed. Mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) values were significantly lower in children with α-thalassemia (α-thal). We came to the conclusion that Hb Stanleyville-II is not so uncommon in Brazil and seems to have originated from the African slave trade. This study reinforces the importance of an accurate diagnosis of variants that have electrophoretic mobility similar to Hb S [ß6(A3)Glu→Val, GAG>GTG] so that false diagnoses are avoided.

Follow-up of children with sickle cell anemia screened with transcranial Doppler and enrolled in a primary prevention program of ischemic stroke.

BACKGROUND: Stroke is a serious complication of sickle cell anemia (SCA). The transcranial Doppler (TCD) is the risk-screening tool for ischemic strokes. The objective of the study was to describe the clinical progression of children with SCA who presented with high risk for stroke by TCD or relevant changes by magnetic resonance angiography (MRA) and underwent the regular transfusion program (RTP) and/or hydroxyurea (HU) treatment between 2007 and 2018. METHOD: This was a neonatal retrospective/prospective cohort study with children born between 1999 and 2014 with the homozygotic form (HbSS) or Sß0-thalassemia who underwent TCD at least once. RESULTS: Of the 718 children screened during this period, 675 had HbSS and 43 Sß0-thalassemia. In 54 children (7.5%), all with HbSS, a high-risk TCD (n = 45) or, when the TCD was inconclusive, an MRA with cerebral vasculopathy (n = 9) was used for detection. Of these, 51 started the RTP and the families of three refused treatment. Of the 43 children with a high-risk TCD who initiated the RTP, 29 (67.4%) reverted to low risk. In 18 of them (62%), HU was started at the maximum tolerated dose (MTD) before transfusion discontinuation. None of these 29 patients had a stroke. Eight children (18.6%) maintained a high-risk TCD, even using the RTP/HU and two had a stroke. CONCLUSIONS: The TCD was confirmed as a viable tool for tracking patients with a risk for stroke. The RTP was effective in preventing the primary event. New strategies are necessary to prevent stroke using HU and new drugs, in addition to bone marrow transplantation.

High reticulocyte count is an independent risk factor for cerebrovascular disease in children with sickle cell anemia.

BACKGROUND: Transcranial Doppler ultrasonography (TCD) is an important way of detecting risk of ischemic stroke in children with sickle cell anemia. PROCEDURE: A random sample of 262 FS-hemoglobin children from a newborn screening inception cohort in Brazil (1998-2005) was followed up to May 2009. Pulsed TCD followed STOP protocol. Children with mean blood flow velocity < 170 cm/sec in cerebral arteries were classified as low risk; between 170 and 184, low conditional risk; between 185 and 199, high conditional risk; and ≥ 200, high risk. RESULTS: Median age, 6.2 years (2-11.2 years); 147 female; 13 children (5%) had ischemic stroke prior to TCD; 186/249 (74.7%) were classified as low risk; 19 (7.6%) as low conditional; 7 (2.8%) as high conditional; and 8 (3.2%) as high risk; inadequate tests, 11.6%. The probability of ischemic stroke at 10 years was 8.3% (SEM 2.3%); of stroke or high-risk TCD 15.6% (3.5%). Children with stroke or altered TCD (conditional and high risk) were compared to children with normal examinations. They were younger (P = 0.03), with lower hemoglobin (P = 0.003), higher leukocytosis (P = 0.015), and higher reticulocytosis (P < 0.001). Episodes per year of acute chest syndrome were also higher in that group, but not significantly (P = 0.09). Reticulocytosis remained the only significant variable upon multivariate analysis (P = 0.004). Basilar and middle cerebral artery velocities were significantly correlated (R = 0.55; P < 0.001). CONCLUSIONS: Probability of stroke was similar to international reports; of belonging to high-risk group, lower. High-reticulocyte count was the most important factor associated with cerebrovascular disease. Basilar artery velocity > 130 cm/sec seems to be an indirect sign of an underlying cerebrovascular disease.

ß-globin gene cluster haplotypes in a cohort of 221 children with sickle cell anemia or Sß°-thalassemia and their association with clinical and hematological features.

BACKGROUND/AIMS: ß(S)-Haplotype prevalence and its associations with clinical and hematological characteristics were assessed in Brazilian children with sickle cell anemia or Sß°-thalassemia. METHODS: A retrospective randomized cohort study was undertaken with 208 SS and 13 Sß°-thalassemia children derived from the Newborn Screening Program of the state of Minas Gerais. ß(S)-Haplotypes were determined by PCR-RFLP. RESULTS: Thirty-nine percent of the SS subjects had the CAR/CAR genotype, 33% had CAR/Ben, 24% had Ben/Ben, 1% had CAR/Atp, 1% had Ben/Atp, and 1% had Arab-Indian/Ben; 1% could not be characterized. Of the Sß°-thalassemia children, 5 were CAR/undefined, 2 were Ben/undefined, and 1 was CAM/undefined. There was no significant association between ß(S)-haplotypes and the total Hb, Hb F, MCV, MCH, WBC, and reticulocyte count among the SS children. Likewise, no significant association was detected between ß(S)-haplotypes and the frequency of acute chest syndrome episodes, blood transfusions, splenic sequestration, or cerebrovascular disease (high-risk/conditional transcranial Doppler ultrasonography or clinical stroke). A limited number of Sß°-thalassemia children precluded valid analyses. CONCLUSIONS: The prevalence of ß(S)-haplotypes in this study is in agreement with the historical records of African slaves brought to the state of Minas Gerais. Furthermore, ß(S)-haplotypes CAR and Ben were not associated with any analyzed feature of children with sickle cell anemia.

Coinheritance of α-thalassemia decreases the risk of cerebrovascular disease in a cohort of children with sickle cell anemia.

The study estimated α-thalassemia (α-thal) prevalence and assessed its associations with clinical and hematological features in a random sample of Brazilian children with sickle cell anemia (208 Hb SS and 13 Hb S-ß°-thal). α-Thalassemia genotyping was carried out by multiplex polymerase chain reaction (m-PCR) for seven alleles. Clinical and hematological data were retrieved from the 221 children's medical files. Their ages ranged from 2.5 to 10.4 years. Of the Hb SS children, 27.9% carried -α(3.7)/αα and 1.4% -α(3.7)/-α(3.7). The presence of α-thal was significantly associated with reduction in MCV, MCH, WBC values and reticulocyte counts. No significant association with blood transfusion or acute chest syndrome (ACS), was found. α-Thalassemia genotypes were strongly associated with reduction in risk for cerebrovascular disease (CVD) (conditional and abnormal transcranial Doppler or stroke; p = 0.007). The interaction of α-thal with other modulating factors should be investigated in order to define subphenotypes of the disease and to use them as clinical tools in the follow-up care of patients.

Frequency of biotinidase gene variants and incidence of biotinidase deficiency in the Newborn Screening Program in Minas Gerais, Brazil.

OBJECTIVE: The prevalence of biotinidase deficiency and the frequency of biotinidase gene variants in Brazil are not documented. We aimed to determine the incidence of partial and profound biotinidase deficiency in the state of Minas Gerais, Brazil, and to calculate the frequency of biotinidase gene variants in the newborn screening program of Minas Gerais. METHODS: Neonates (1,168,385) were screened from May 2013 to June 2018. Those detected with abnormal biotinidase activity based on semi-quantitative assays underwent confirmatory serum tests. The biotinidase gene was sequenced in all confirmed cases. RESULTS: The combined incidence of partial and profound biotinidase deficiency was estimated at 1:13,909 live births (95% confidence limit 1:11,235-1:17,217), much higher than the incidence rates reported in other populations worldwide. The most frequent biotinidase gene variants were p.D444H (allele frequency, 0.016), haplotype c.1330G>C;c.511G>A (p.D444H;A171T), p.D543E, c.310-15delT (intronic), p.V199M, and p.H485Q. Together these accounted for 74.6% of the alleles analysed. CONCLUSION: Newborn screening for biotinidase deficiency, which revealed a higher incidence in Minas Gerais, is feasible and plays a critical role in the early identification of affected neonates and prevention of symptoms and irreversible sequelae. Biotinidase gene sequencing is a useful tool to confirm the diagnosis, and also provides valuable information about genetic variability among different populations.