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.

Primary nephrogenic diabetes insipidus (NDI) is a genetic, chronic disease characterised by lack of distal renal tubule to antidiuretic hormone. The condition produces polyuria, polydipsia, and consequently, reduced caloric intake and growth failure. There is very scarce information on physical growth of affected children. The objective of the paper is to describe long-term growth of 14 patients from 11 families, studied retrospectively and followed for 3-16 years (median 11.6 years). Diagnosis was made on the basis of clinical and laboratory data and concentration test under pitressin. Patients were treated with indomethacin, thiazides, and amiloride. Weight and standing height was measured periodically at the Laboratory of Anthropometry, following standardised techniques. Information was obtained from clinical notes. The majority of children grew below the third centile of local standards, and many showed improvement of weight, height, and body mass index (BMI) over time. Mean height, weight, and BMI gain during follow-up was 1.72, 1.06, and 1.46 standard deviations (SDs), respectively. Three children who did not adhere to treatment showed growth delay. Height gain during the first 2 years of follow-up was inversely associated with height deficit at diagnosis. Further studies on growth at adolescence and in different mutations are recommended.

Growth is a discontinuous and irregular process, present not only in long bones but also in skull bones. Although long-term growth curves of head circumference and supine length are different, when measured on a daily basis findings suggest that skull and long bones have a common pattern; the physiological basis needs future research.

Our findings support the concept of growth as a non-linear and irregular process with three phenomena: Stasis, steep changes and continuous growth present in all ages, including infancy, school age and adolescence.

Skeletal dysplasias (SD) are disturbances in growth due to defects intrinsic to the bone and/or cartilage, usually affecting multiple bones and having a progressive character. In this article, we review the state of clinical and research SD resources available in Latin America, including three specific countries (Brazil, Argentina, and Chile), that have established multidisciplinary clinics for the care of these patients. From the epidemiological point of view, the SD prevalence of 3.2 per 10,000 births from nine South American countries included in the ECLAMC network represents the most accurate estimate not just in Latin America, but worldwide. In Brazil, there are currently five groups focused on SD. The data from one of these groups including the website www.ocd.med.br, created to assist in the diagnosis of SD, are highlighted showing that telemedicine for this purpose represents a good strategy for the region. The experience of more than 30 years of the SD multidisciplinary clinic in an Argentinian Hospital is presented, evidencing a solid experience mainly in the follow-up of the most frequent SD, especially those belonging the FGFR3 group and OI. In Chile, a group with 20 years of experience presents its work with geneticists and pediatricians, focusing on diagnostic purposes and clinical management. Altogether, although SD health-care and research activities in Latin America are in their early stages, the experience in these three countries seems promising and stimulating for the region as a whole.