Sirenomelia: An anatomical assessment and genetic sex determination of two cases.

The etiology of sirenomelia is currently unknown. Data are limited in comparing external and internal abnormalities using modern imaging technologies and molecular genetic analysis. The purpose of the current study was designed to compare external and internal anatomical defects in two cases of sirenomelia and Potter's sequence. Considered rare, Potter's sequence is a fetal disorder with characteristic features of bilateral renal agenesis, obstructive uropathy, atypical facial appearance, and limb malformations. The internal and external malformations of two term fetuses with sirenomelia and Potter's sequence were compared using assessment of external features, radiography and MRI on internal structures, and molecular genetic studies on sex determination. Data reveal that both fetuses were male and manifested with an overlapping but distinct spectrum of abnormalities. Principal differences were noted in the development of the ears, brain, urogenital system, lower limbs, pelvis, and vertebral column. Defects of the axial mesoderm are likely to underlie the abnormalities seen in both fetuses. The first one, which had only caudal defects, was found to have a spectrum of abnormalities most similar to those associated with more severe forms of the small pelvic outlet syndrome, although the structure and orientation of the sacrum and iliae were different from previously reported cases. The other had both caudal and cranial defects, and was most similar to those described in the axial mesodermal dysplasia syndrome. Defects associated with sirenomelia can be evaluated with standard gross anatomy examination, radiology, MRI, and modified PCR techniques to determine anatomical abnormalities and the sex of preserved specimens, respectively. Evidence indicated that sirenomelia could be developed via various etiologies.

Mixed phenotype acute leukemia, B/myeloid, NOS with near-tetraploidy: a case report.

Acute leukemia in adults is usually associated with a myeloid phenotype, and less commonly presents as an acute lymphocytic leukemia. Rarely, the leukemic blast cells express more than one lineage phenotype and satisfy the diagnostic criteria for an acute leukemia of ambiguous lineage (ALAL), further subclassified as mixed phenotype acute leukemia (MPAL). Near-tetraploidy is an unusual presentation of acute leukemia where the blasts contain 80-104 chromosomes. More commonly associated with acute lymphocytic leukemia, near-tetraploidy has been described in only a limited number of cases of acute myeloid leukemias, and near-tetraploid ALAL is rare. We describe the first report of near-tetraploid MPAL, B/myeloid, not otherwise specified.

Melanocortin-4 Receptor Deficiency Phenotype with an Interstitial 18q Deletion: A Case Report of Severe Childhood Obesity and Tall Stature.

Childhood obesity is a growing health concern, associated with significant physical and psychological morbidity. Childhood obesity is known to have a strong genetic component, with mutations in the melanocortin-4 receptor (MC4R) gene being the most common monogenetic cause of obesity. Over 166 different MC4R mutations have been identified in persons with hyperphagia, severe childhood obesity, and increased linear growth. However, it is unclear whether the MC4-R deficiency phenotype is due to haploinsufficiency or dominant-negative effects by the mutant receptor. We report the case of a four-and-a-half-year-old boy with an interstitial deletion involving the long arm of chromosome 18 (46,XY,del(18)(q21.32q22.1)) encompassing the MC4R gene. This patient presented with tall stature and hyperphagia within his first 18 months of life leading to significant obesity. This case supports haploinsufficiency of MC4-R as it describes a MC4-R deficiency phenotype in a patient heterozygous for a full MC4R gene deletion. The intact functional allele with MC4-R haploinsufficiency has the potential to favor a therapeutic response to gastric surgery. Currently, small molecule MC4-R agonists are under development for pharmacologic therapy.

A model for GFR alpha 4 function and a potential modifying role in multiple endocrine neoplasia 2.

Mutations of the RET proto-oncogene are found in the majority of patients with the inherited cancer syndrome multiple endocrine neoplasia type 2 (MEN 2). A minority of cases, however, have no detectable RET mutation and there is considerable phenotypic variation within and among MEN 2 families with the same RET mutation, suggesting a role for other loci in this disease. A candidate for such a gene is glial cell line-derived neurotrophic factor receptor alpha 4 (GFRA4), which encodes a cell surface-bound co-receptor (GFR alpha 4) required for interaction of RET with its ligand persephin. The GFRA4 gene has multiple alternative splices leading to three distinct protein isoforms that are prominently expressed in thyroid. We postulated that mutations of GFRA4 contribute to MEN 2 in the absence of RET mutations or modify the RET mutation phenotype. We screened patients with MEN 2 or MEN 2-like phenotypes, with and without RET mutations, for variants of GFRA4. We identified 10 variants, one of which was over represented in, and two of which were found exclusively in, our patient populations. One of these was a single-base substitution upstream of the GFR alpha 4 coding region, where it may alter gene expression. The second was a 7 bp insertion, which results in a change in reading frame for all three GFR alpha 4 isoforms. This would cause a relative shift in membrane bound and soluble forms of GFR alpha 4, which would significantly alter the formation of RET signalling complexes. Our data suggest a model of wild-type GFR alpha 4 isoform expression that includes both activating and inhibiting co-receptors for RET.