Widespread retinal degenerative disease mutation (rdAc) discovered among a large number of popular cat breeds.

The recent discovery of a mutational variant in the CEP290 gene (CEP290: IVS50+9T>G), conferring recessive retinal degeneration in Abyssinian and Somali (long-haired Abyssinian) cats (rdAc) prompted a survey among 41 cat breeds (846 individuals) to assess the incidence, frequency and clinical consequence of rdAc. The rdAc allele displayed widespread distribution, observed in 16/43 (37%) breeds, exhibiting a high allele frequency (∼33%) in North American and European Siamese populations. Clinical evaluations demonstrated high concordance between rdAc pathology and the CEP290 (IVS50+9T>G) homozygous genotype (P=1.1E-6), with clinical disease similar to affected Abyssinians/Somalis. This retinal degeneration has not been reported in breeds other than the Abyssinian/Somali and poses a significant health risk particularly in the Siamese breed group. Alertness of the veterinary community and the present availability of commercial diagnostic testing could synergistically enable breeders to reduce the incidence of rdAc blindness in pure-bred cat populations.

Reference weights for placentas delivered before the 28th week of gestation.

CONTEXT: Very few studies have measured the weight of large numbers of placentas delivered before the 28th post-menstrual week. METHODS: We measured the weight of 930 singleton placentas delivered before the 28th post-menstrual week, and examined the distributions of weights in selected groups (week of gestation, reason for preterm birth, birth weight Z-score categories, placenta histology). We excluded 90 singleton placentas based on growth restriction as indicated by birth weight Z-score, resulting in a normative sample of 840 placentas. Weights for unfused twin placentas are also presented. RESULTS: Standard weights derived from our data set differ from those previously published, partly due to a larger sample size. Placenta weight varied with birth weight. Placentas from pregnancies ending due to preeclampsia, fetal indications or those showing evidence of poor perfusion on histology were among the smallest and their weights correlated with the smallest birth weights for gestational age. CONCLUSIONS: Placenta weights appear to be influenced by multiple maternal and fetal processes. We present a standard weight table for singleton placentas among live infants born between 23 and 27 completed weeks.

Recurrent umbilical cord torsion leading to fetal death in 3 subsequent pregnancies: a case report and review of the literature.

During a span of 3.5 years, a 30-year-old, gravida 9, para 3 woman experienced 3 pregnancies complicated by umbilical cord torsion and constriction. In each case, the complication resulted in acute vascular compromise and intrauterine fetal demise. Gross examination disclosed cord constriction and torsion at the fetal end of the cord in each instance. Histologic sections from the cord torsion sites demonstrated fibrosis and deficiencies in Wharton's jelly in each case. Cytogenetic studies prepared using fetal villous tissue demonstrated normal karyotypes in fetal cells from the first 2 pregnancies (46,XX and 46,XY, respectively). The karyotype from the third pregnancy showed a 46,XX,del(X)(q24) mutation in 3 of 15 cultured cells, while 12 of 15 cells possessed a normal 46,XX karyotype. This cytogenetic abnormality was not believed to represent the cause of fetal demise in this case. To our knowledge, this is the first report of umbilical cord torsion in 3 pregnancies within one family. The familial clustering observed in this report suggests that a genetic predisposition for umbilical cord torsion may exist in some cases.

Reproduction in a patient with trisomy 8 mosaicism: case report and literature review.

We describe a patient with trisomy 8 mosaicism followed through a sixth pregnancy and discuss issues in phenotypic and genotypic variability, the risk for neoplasia, and reproductive risks.

A five-year experience with fragile X testing. Setting laboratory standards of practice and a cost-effective protocol.

During the years 1990-1994, our center tested 652 patients, with a broad range of referral indications, for fragile X syndrome using either cytogenetic analysis alone (Protocol 1) or more recently, a combination of DNA analysis and routine karyotyping (protocol 2). The overall positive rate for fragile X was 3.1% with an incidence of other chromosomal abnormalities (OCAs) of 3.2%. Breakdown of cases using each testing protocol along with percent positives is: [table: see text] Use of Protocol 2 yielded only definitive fragile X results, while more than half of the "positives" using Protocol 1 were equivocal. Historically this has been problematic for both the laboratory and physician since interpretation is often dependent on an equally equivocal clinical picture. Protocol 2 eliminates these diagnostic dilemmas without compromising detection of other chromosomal abnormalities, the incidence of which appears to be unaffected by testing method used. The overall incidence of OCA of 3.2% underscores the value of routine karyotyping in this referral group and likely reflects the phenotypic variability of fragile X and its clinical overlap with other chromosomal abnormalities. We believe that a fragile X testing protocol combining routine karyotyping with definitive molecular technology represents the most cost-effective diagnostic approach to this clinically challenging patient population.

Inheritance of polycystic kidney disease in Persian cats.

Polycystic kidney disease in Persian cats culminates in chronic renal failure after a variable clinical course. An affected 6-year-old Persian cat was used to establish a colony of cats with polycystic kidney disease. In affected cats, cysts could be detected by ultrasonography as early as 7 weeks of age. Absence of cysts on ultrasound examination at 6 months of age was correlated with absence of polycystic kidney disease at necropsy. Both males and females were affected and, of progeny from affected x unaffected crosses, 42% were affected and 58% were unaffected. In affected x affected crosses, 73% of progeny were affected and 27% were unaffected. These results are compatible with autosomal dominant inheritance of this trait. Polycystic kidney disease in Persian cats resembles autosomal dominant polycystic kidney disease (ADPKD) in human beings, and represents a valuable animal model of the human disease.

Trisomy 7 and Potter syndrome.

A patient with mosaic trisomy 7 and features of Potter syndrome is described. The patient was the product of a 35-week gestation and survived fourteen hours, demise being attributed to respiratory insufficiency. Autopsy confirmed pulmonary hypoplasia and renal agenesis. Additional findings included malformed, low-set ears, a flattened nasal bridge, redundant nuchal skin, positional deformation of the extremities, rocker-bottom feet, and clitorimegaly. Cytogenetic study of peripheral blood and skin fibroblast culture revealed mosaicism for full trisomy 7, the skin showing 12% of the cells to have an extra 7. Comparison with one previously confirmed case of trisomy 7 and two cases of trisomy C suggests a correlation between trisomy 7 and Potter syndrome.