Clinical-etiologic correlation in children with Prader-Willi syndrome (PWS): An interdisciplinary study

Prader-Willi syndrome (PWS) is a multisystemic disorder caused by the loss of expression of paternally transcribed genes within chromosome 15q11-q13. Most cases are due to paternal deletion of this region; the remaining cases result from maternal uniparental disomy (UPD) and imprinting defects. To better understand the phenotypic variability of PWS, a genotype-phenotype correlation study was performed in 91 children with PWS. Patients were diagnosed by Southern Blot Methylation assay and genetic subtypes were established using FISH and microsatellite analyses. Fifty-nine subjects with deletion (31/28 males/females; mean age 3.86 years), 30 with UPD (14/16 males/females; mean age 3.89 years) and 2 girls with a presumed imprinting defect (mean age 0.43 yrs) were identified. For correlation purposes patients were grouped as "deleted" and "non-deleted." An increased maternal age was found in the UPD group. Four of Holm's criteria were more frequently present in the deleted group: need for special feeding techniques, sleep disturbance, hypopigmentation, and speech articulation defects. Concerning cognitive assessments, only 9.52% of subjects with deletion had Full-Scale IQ (FSIQ) > or =70, while 61.53% of subjects without deletion had FSIQ > or =70. Similar results were found in behavioral measures. Sleep disorders and carbohydrate metabolism were systematically assessed. Polysomnoghaphic studies revealed a higher frequency of central events with desaturations > or =10% in the deleted group (P = 0.020). In summary, the phenotype was significantly different between both groups in certain parameters related to the CNS. These results might be related to the differences in brain gene expression of the genetic subtypes.

Characterization of alterations in carbohydrate metabolism in children with Prader-Willi syndrome

OBJECTIVE

To study carbohydrate metabolism and insulin sensitivity and secretion in children and adolescents with Prader-Willi syndrome (PWS) compared with multifactorial obesity (MO) controls.

PATIENTS AND METHODS

Seventy-five patients with PWS and 395 controls with MO were studied by oral glucose tolerance test. Insulin resistance (IR) and beta-cell function were assessed by homeostasis model assessment (HOMA), insulin glucose index, fasting insulin and insulin sensitivity index.

RESULTS

The incidence of diabetes mellitus was 0% in PWS and 1.5% in MO, while carbohydrate intolerance was 9.3% in the former group and 7.6% in the latter (NS); basal insulin level (12 +/- 8.2 vs 22.3 +/- 25 mU/ml) and HOMA-IR (2.47 +/- 1.6 vs 4.18 +/- 5.05) were lower in PWS (p = 0.004 and 0.04, respectively), whereas HOMA beta-cell index was lower in PWS than in MO (59 +/- 42 vs 102 +/- 119, p = 0.03). ISI Composite was higher in PWS compared to MO (6 +/- 5.7 vs 4.18 +/- 5.05, p = 0.04).

CONCLUSION

Patients with PWS presented lower insulin resistance and a dissociation between beta-cell secretion and the degree of obesity.

Prevalence of type 2 diabetes mellitus and impaired glucose tolerance in obese Argentinean children and adolescents

The aim of this study was to evaluate the prevalence of type 2 diabetes mellitus (DM2) and impaired glucose tolerance (IGT) in obese children and adolescents and to examine insulin resistance and insulin secretion. We studied 427 asymptomatic obese patients. DM2 and IGT were diagnosed by an oral glucose tolerance test. Insulin resistance and P-cell function were assessed by using homeostasis model assessment (HOMA), insulin/glucose index (I/GI), fasting insulin and insulin sensitivity index (ISI-composite). Thirty patients showed IGT (7%) and seven had DM2 (1.6%). The mean age was 10.7 +/- 3.5 years, the diabetic group being significantly older than the normal group (p < 0.01). The mean body mass index was 30 +/- 5.3 kg/m2 without significant differences between groups. beta-Cell function declined significantly in the patients with IGT and DM2, and insulin resistance increased significantly. Given the rather high prevalence of glucose metabolism impairment, children with obesity should undergo glucose tolerance testing for appropriate therapeutic intervention.

[Evaluation of an intensive treatment education program for type 1 diabetes in a group of adolescents. A two year follow up]

During the past decade several reports were published showing that intensive treatment of type 1 diabetes can prevent and delay disease-related microvascular complications. However, several problems were reported in children and adolescents such as frequent hypoglycemic episodes and weight gain. The aim of this study was to describe the results of intensified treatment for type 1 diabetes in a group of Argentinean adolescents after a follow-up of two years. Twenty five adolescents with type 1 diabetes older than 10 years with at least one year from diagnosis were selected. All patients received a one-week teaching program during admission to our center. All patients were followed-up monthly during two years. Treatment schedule included 4-5 controls in fasting conditions, two doses of NPH insulin and four doses of regular insulin according to glycemia and the amount of calculated carbohydrate intake. Median age was 13.5 years (range 10 to 19 years). Mean time from diagnosis to inclusion in the study was 3.8 years (range 1.25 to 9 years). Mean total dose of NPH insulin decreased significantly when measured at the inclusion in the study (0.9 IU/kg) and after a year of follow-up 0.8 IU/kg (p 0.04). However, there were no changes in NPH insulin dose after two years follow-up (0.85 IU/kg). On the contrary, the dose of regular insulin administered on fasting conditions with normal glycemia increased from 0 to 0.21/kg after a year (p 0.0001) and to 0.69 after two years (non significant). Median HbA1C showed a significant reduction from 10 +/- 1.62% to 8.53 +/- 1.04% after a year (p 0.03) and to 8.72 +/- 0.81% after two years. BMI Z score increased from significantly from 0.7 +/- 0.9 to 1.06 +/- 1.15 after a year (p 0.03) with a further reduction without a significant difference from the basal value after two years. We found no significant differences in the frequency of hypoglycemia or other metabolic features. Our results show that intensive treatment of type 1 diabetes in children and adolescents can achieve significant and sustained reductions of HbA1C without increasing the risk of hypoglycemia or other adverse effects.

[Beta thalassemia major in Argentina]

An analysis of beta thalassemia major patients seen at Hospital Juan P. Garrahan was carried out in order to determine the characteristics and outcome of the population. From August 1987 to July 2000, 45 patients were admitted (27 males-18 females). The most common beta globin gene defects were C-39 (30.7%); IVS-I nt 110 (20%); IVS-I nt 6 (13.3%); IVS-I nt 1(4%). alpha globin genes were normal in 42 patients, 1 patient had triplicate and cuadriplicate alpha globin genes and 2 patients were not analyzed. Six patients of 5 families were heterozygous for -158G gamma mutation. Allogeneic stem cell transplantation was performed in 7 patients, with an identical sibling. Transfusion-related infections and alloantibodies were detected in 6.7% patients. Growth assessment showed no significant difference in the stature of girls compared to the reference population, but 5 boys had short stature. There is a tendency to short trunk. Growth velocity was normal at prepubertal age. No X-ray lesions related to desferrioxamine were observed. Delayed puberty and hypogonadotropic hypogonadism were found in 35.7% and abnormalities in GH/IGF-I axis in 12.5% of the patients. Impaired glucose tolerance was found in 2 patients. No patient developed diabetes mellitus, thyroid or adrenal insufficiency. One patient had cardiac complications. Forty-two patients are alive and 3 died (cardiac failure 1, central nervous system bleeding 1, sepsis 1). We conclude that beta thalassemia major, originated mainly from Italian immigrants, has a cumbersome treatment and is severely hindered by the lack of adequate economic resources in our patients.

Immunologic and genetic markers in insulin-dependent diabetes mellitus (type 1) in an Argentine population

The objective was to evaluate the prevalence and association of several markers (islet cell antibodies: ICA, insulin autoantibodies: IAA, glutamic acid decarboxylase antibodies: GADA and ICA512 antibodies: ICA512A) along with HLA DQB1 genotype in type 1 diabetes mellitus of recent onset, including siblings and individuals without any history of this disease, in an Argentine population. A total of 79 children with type 1 diabetes mellitus of recent onset were studied, as well as 79 control children, and 68 healthy siblings of type 1 diabetic cases. IAA, ICA, GADA, ICA512A and HLA DQB1 alleles were determined. Sensitivity was 67.1% for ICA, 36.7% for IAA, 74.6% for GADA and 63.4% for ICA512A. None of the control subjects was positive for the immunological markers. Combined sensitivity of ICA-IAA-GADA was 89.8%, similar to the ICA512A-GADA (87.3%) or ICA512A-GADA-IAA combination (91.1%). GADA correlated positively with ICA, but no such correlation was found between IAA, ICA512A and ICA. IAA correlated negatively and GADA positively with age. IAA was associated to DQB1*0201, whereas ICA and ICA512A associated to DQB1*0302. Among siblings, 3/68 (4.4%) were positive for IAA and a single case (1.5%) was positive for GADA and one for ICA512A. Our findings show that the combination of multiple tests increases the sensitivity for prediction, with the ICA512A-GADA combination proving highly sensitive and equivalent to other proposed combinations, such as ICA-IAA-GADA.