Salmonella appendicitis in renal transplantation.

While appendicitis remains one of the commonest surgical diseases, there are relatively few reports following renal transplantation. A 33-year-old man was admitted with diarrhea, fever, and epigastric pain 7 years following a cadaveric renal transplant. CT scanning confirmed a diagnosis of appendicitis which was removed within 24 hours of admission. Histology and blood cultures following surgery confirmed Salmonella type b appendicitis. Patient was safely discharged home 5 days following hospital admission.

Significance of a prenatally diagnosed del(10)(q23).

Structural chromosome mosaicism is rare. We report a case of prenatal mosaicism for a deletion of chromosome 10(q23). To our knowledge, there are only three reports of prenatally diagnosed cases of del(10)(q23). Two of these cases were due to an inherited fragile site. In the present case amniocentesis revealed 46,XY,del(10)(q23)[9]/46,XY[45]. Follow-up chromosome analysis of peripheral blood and placental tissue from a phenotypically normal liveborn male revealed the del(10)(q23) in only 3/100 blood cells grown in low-folate medium. It appears that prenatally diagnosed deleted (10q) mosaicism represents culture artifact and is not clinically significant.

Probing the human genome in search for a new 3q syndrome.

We report a case of partial trisomy 3q syndrome which could not be clinically identified as a distinct entity. The major clinical findings include: psychomotor delay with behavioral problems, coarse facial features, frontal bossing, bushy eyebrows, prominent ears, a small upturned nose and a history of repaired inguinal hernia. There was an additional material on chromosome 4, which could easily be matched with bands 18q21.2-q22; 2p24-p25; 16p21-p23; 10p12-p14; 20q12-q13.2; 15q25-q26.2; 8p23-p24.2 and 6p22.3-p24 and a new syndrome could apparently be suggested based on GTG techniques alone. Nevertheless, by FISH technique, the extra segment was identified as a part of 3q26.3-qter. We provide an extensive review of trisomy 3q syndrome and present a caveat of the consequences of description of new syndromes based on routine banding techniques especially in situations where the origin of chromosomal abnormalities is de novo or parents are not available for cytogenetic evaluation.

Pericentromeric heteromorphism of human chromosome 18 as revealed by FISH-technique.

The pericentromeric heterochromatin contains tandemly repeated alphoid DNA sequences of about 171 bp in length. They are highly divergent from one chromosome to another due to chromosome specific alphoid subsets. In the present investigation, we used chromosome 18-specific centromeric probe (D18Z1) to evaluate the extent of pericentromeric heteromorphism classified by FISH-technique among 25 normal individuals. The hybridization signals were arbitrarily classified into five sizes when compared with the length of the short arm of chromosome 18. These are: negative (1), small (2), medium (3), large (4), and very large (5), with incidence of 0, 12, 24, 42, and 22 percent, respectively. Based on limited data, there were no chromosomes with negative signals while 42% of chromosome 18 had large-sized pericentromeric heterochromatin. The incidence observed earlier by restriction endonuclease Alu1 was different as compared to the present approach suggesting the complex heterogeneity of pericentric region of chromosome 18.

Chromosomal mosaicisms during prenatal diagnosis.

Chromosomal mosaicism during prenatal diagnosis has been a major concern. Nondisjunctional events can lead to mosaicism in a number of ways, including failure of chromosomal pairing, failure to separate, anaphase lag and abnormal segregation. We provide a concise review on various types of mosaicism with their clinical significance.

Characterisation of a satellited non-fluorescent Y chromosome (Y[nfqs]) by FISH.

A fetus was prenatally diagnosed as having a Y(nfqs) chromosome which was inherited from the father. With the QFQ technique, the Yqh was observed to be nonfluorescent and contained cytological satellites which were attached to the terminal long arm. The satellites were positively stained by the Ag-NOR technique suggesting that the NORs were active. A battery of DNA probes was used to characterise the Y(nfqs). Hybridisation experiments using a chromosome 15 specific classical satellite DNA probe (D15Z1) and a Yq telomere DNA probe showed that the additional satellited material on Yq originated from 15p, and that the Yq terminal region had been lost. This is the first reported case in which the origin of cytological satellites on Yq has been determined by FISH, but this does not imply that all satellited Y chromosomes are derived from 15p. However, the clinical significance of this Y(nfqs) chromosome remains obscure.

Marker chromosomes in fetal loss.

The clinical significance of marker chromosomes has remained obscure especially when diagnosed prenatally. Some carriers have terminated their pregnancies. Extensive attempts have been made to characterize these chromosomes whose origin is frequently difficult to ascertain. This brief summary presents an overview of the implications for fetal loss.

Delineation of a ring chromosome 16 by the FISH-technique: a case report with review.

We report on a new case with ring chromosome 16. Initially, the cytogenetic findings with GTG-banding revealed a 46,XY,r(16)(::p13.3-->q24::)/46,XY karyotype. This is the first case of r(16) co-existing with a normal cell line with minimal clinical consequences. The ring appeared to be monocentric and stable. A ring chromosome can result in a loss of varied segments of one or both chromosome arms or may involve telomere-telomere fusion without loss of genetic material. Thus it was imperative to use the latest molecular cytogenetic techniques for evaluation of this ring chromosome. It is believed that the ring chromosome retained specific telomeric sequences unique to 16q and that there was no loss of genetic material during the ring formation. Apparently, either a 16p telomere-16q telomere fusion or a fusion between the 16q telomere and a distal segment of the 16p13 band may explain the mechanism of ring formation. In either case, loss of genetic material is assumed to be negligible. A more descriptive karyotype of the proband was determined to be: 46,XY,r(16)(::pter or ::p13.3-->qter::)/46,XY. The fluorescent in-situ hybridization technique using various DNA probes provided this finer characterization.

Centromeric alphoid DNA heteromorphisms of chromosome 21 revealed by FISH-technique.

The centromeric heterochromatin of chromosome 21 has been evaluated by the fluorescence in situ hybridization (FISH) technique. It was found that the alphoid DNA sequences of pericentromeric regions of chromosome 21 were highly heteromorphic when a centromeric specific probe was hybridized to these sequences. The variations were so extreme that they could even be arbitrarily classified into at least five sizes by comparison with the length of the short arm (p) of chromosome 18. They are negative (1); small (2); medium (3); large (4); and very large (5). We used 15 normal cases and 12 individuals with trisomy 21 (Down syndrome), and the incidences for these five classes were 3.0%, 22.7%, 59.2%, 13.6% and 1.5%, respectively. At least 3% of the chromosomes no. 21 did not show any trace of hybridization signals, which apparently escape detection at interphase level as well. Although, the variations observed in the present study are continuous, the proposed classification may yield some implications for future investigations.

Paracentric inversion involving the long arm of chromosome 9 resulting in deletion of abl gene.

We report on a new chromosomal finding in a newborn male with hypertelorism, apparently low-set malformed ears with patent canal, micrognathia with narrow high-arched palate, bilateral webbing of neck with low posterior hairline, widely spaced nipples, and complex heart anomalies. Initially, what appeared to be a simple paracentric inversion of the long arm of chromosome 9, that is, 46,XY, inv(9)(q31q34) by routine GTG-banding technique was later determined to be a paracentric inversion with deletion of the band 9q34.1 by FISH technique using an abl unique sequence DNA probe. Thus the cytogenetic diagnosis was modified to 46,XY,der(9) inv(9)(q31q34.1)del(q34.1). Nevertheless, the presence of telomeric repeat sequences in the inverted chromosome 9 suggests that either healing has occurred by adding [TTAGGG]n sequences to the non-telomeric end (q31) by the enzyme telomerase or telomeric sequences were not affected during this inversion process. This abnormality is a rare occurrence and has never been reported before either because of a high rate of lethality or it has been undetected by routine cytogenetic techniques. The other abnormal cases with apparent paracentric inversions could also have a complex nature with congenital anomalies associated with loss of "few" DNA sequences as exemplified here.

Characterization of two extreme variants involving the short arm of chromosome 22: are they identical?

The heteromorphic nature of the short-arms of human acrocentric chromosomes is considered the norm without any dire consequences. We characterized two highly unusual chromosome 22 variants with extremely enlarged short arms by routine and molecular cytogenetic techniques. Routine banding revealed that the two variants were not alike. Therefore, a characterization by fluorescent in situ hybridization (FISH) technique became warranted and revealed their remarkable differences. The first variant apparently had a tandem duplication of bands p11.2-->p13, while the second variant had a loss of the beta-satellite and ribosomal DNA regions with an apparent amplification of the satellite III region. The formation of these extremely enlarged regions can occur by a variety of mechanisms whose clinical significance remains obscure.

Characterization of an isodicentric Y-chromosome for the long arm in a newborn with mixed gonadal dysgenesis.

A newborn infant was referred for evaluation because of ambiguous genitalia. Examination of the genitalia revealed a hypospadiac phallus measuring 1.5 cm in length with chordee. Subtle phenotypic features consistent with Turner syndrome were present including hypertelorism, anti-mongoloid slant to the eyes, mild widening of the neck, but no definitive webbing, shield like chest and positive cubitus valgus. A pelvic and renal sonogram confirmed the presence of a uterus and normal-appearing kidneys. There was incomplete fusion of the scrotum. No gonads were palpable within the scrotal sac. The patient was assigned a female gender on the basis of the presence of a uterus, the phenotypic appearance of the genitalia and the malignant potential of the gonads. The cytogenetic findings with QFQ-banding revealed an abnormal karyotype, i.e., mos 46,X,idic(Y) (p11.2)[77]/45,X[29]/46,X,idic(Y) (p11?) [2]/ 47,XY,idic(Y)(p11.2)[2]/47,X,idic(Y)(p11.2), + idic(Y)(p11.2)[1]/46,XY[1]. The presence of an abnormal isodicentric Y-chromosome was evaluated by FISH-technique to ensure a finer characterization than routine methods. The genotype-phenotype correlation could not be established since mosaicisms of highly variable nature can exhibit an unpredictable outcome.

Tandem duplication of chromosome 14 (q12q13).

A nine-years-old Egyptian boy was referred for speech and language delay. He has an I.Q. of 35 which is in the moderately to severely delayed range. Routine cytogenetic and FISH-techniques revealed a de novo tandem duplication of chromosome 14 bands q12 and q13, i.e., 46, XY, dup (14)(q12q13) and there are no investigations reporting a direct de novo duplication for this region.

An unusual G-negative band within 1qh region a rare variant or an abnormality?

Morphological variations due to heterochromatic DNA of the secondary constriction region (qh) of human chromosome 1 are considered normal. The structural abnormalities involving or in association within the qh region have been difficult to characterize by routine cytogenetic methods and in turn have often gone undetected. In the past, the presence of a G-negative band within the qh region of chromosome 9 has been considered as a rare or unusual variant. Fortuitously, we were referred two cases where a G-negative band was embedded within the secondary constriction region of chromosome 1. Whole chromosome #1 specific painting probe, did hybridize to the band. Both patients have speech delay. Unfortunately, the parents were not available to confirm the mode of inheritance, nor could a definite conclusion be reached concerning its morbidity. Nevertheless, we are tempted to hypothesize that this is an unusual variant where a G-negative band apparently became genetically inert when it was sandwiched between two blocks of heterochromatin. Similar to a rare variant of chromosome 9 it could be found in the qh region of chromosome 16 as well, whose clinical consequences remain obscure.

Variant euchromatic band within 16q12.1.

The enlarged short arm of chromosome 16 resulting in an additional euchromatic band has been regarded as a variant. We present an unreported case with an unusual variant of chromosome 16, where the mother and daughter both have an additional band (q12.1) in the long arm. Its origin is chromosome 16, as revealed by FISH-technique, and its familial nature suggests that it has no clinical significance.

Molecular characterization of an unusual variant of the short arm of chromosome 15 by FISH-technique.

One of the most frequent translocations involving the long arm of chromosome Y with autosomes is with the short arm of chromosome 15. The regions which are involved in this translocation fluoresce brightly, are highly heteromorphic and thus escape detection. Therefore, these abnormalities could not be fully characterized, especially in cases where parents are not available or paternity is disputed. Results from the employment of the selective staining techniques DA/DAPI and Q-banding have been inconclusive. FISH-technique using whole chromosome painting (WCP) probes should be used to decipher such translocations. We present a case where, even after using a battery of probes, the origin of extra material on chromosome 15p could not be identified though it was not a part of Yq.

Molecular characterization of 21p- variant chromosome.

Fortuitously, within a 1-month period, we were referred two individuals for routine cytogenetic amniocenteses involving one chromosome 21 from each patient, which had apparently lost the entire short arm and a major portion of the centromeric alphoid sequences in their amniocytes. Breakage may have occurred within alphoid sequences resulting in extreme variants. Variations of a similar nature were originally referred to as Christchurch (Ch1) chromosomes and have been wrongly determined to be abnormal. The 21p- chromosome variants were similar in both cases, though they are from unrelated individuals. These rare variants, whose origins were both maternal and have no clinical consequences, were characterized by the FISH-technique to provide a greater degree of certainty.

A de novo interstitial deletion of chromosome 15 band q25 as revealed by FISH-technique.

We report a new chromosomal finding in a 20 month-old girl. The minor clinical features included: moderate mental retardation, microcephaly, mild hypotonia and hypertelorism. Initially, what appeared to be a terminal deletion of the long arm of one chromosome 15 [15q26-->qter] was determined to be an interstitial deletion involving band 15q25 as revealed by FISH-technique, showing the presence of intact telomeric hybridization signals. The cytogenetic diagnosis was thus modified to 46,XX, del (15) (pter-->q24::q26--> qter). Nevertheless, the function of the enzyme telomerase should not be ignored, as healing could occur following such terminal deletions. Consequently, it will remain a difficult task to distinguish terminal deletions from those that are interstitial.

Retrieval of aneuploidy by FISH-technique in a case with 46,XX/47,XXX/47,XX,+8.

We report on a 46 year old female with a new chromosomal finding [46,XX/47,XXX/47,XX,+8] who was referred for ovarian failure. The clinical presentation was highly unusual and the patient does not exhibit the characteristic phenotype of trisomy 8 syndrome. Interphase cytogenetics using FISH-technique revealed discrepancies with a different population of cells when compared with its metaphase index. Therefore, it is advised that patients with mosaic karyotypes should be evaluated by analyzing metaphase as well as interphase nuclei labeled with chromosome specific molecular tags, especially in the situations where the incidence of a mosaic cell line is very low. Nevertheless, in a cost-conscious environment, we must exercise caution prior to making universal recommendations concerning the usefulness of medical devices which are increasing at a logarithmic rate.