Pre-implantation diagnosis

The access to human pre-implantation embryos that is afforded by procedures now developed for the treatment of infertility presents the possibility of very early prenatal diagnosis, before implantation in the uterus, of certain genetic diseases. Only the normal embryos would be replaced in the mother for initiation of implantation and pregnancy. Early experiments on a mouse model for Lesch-Nyhan syndrome (HPRT-deficiency) show that pre-implantation diagnosis of genetic disease is feasible.     

Laboratory diagnosis of SARS

The emergence of new viral infections of man requires the development of robust diagnostic tests that can be applied in the differential diagnosis of acute illness, or to determine past exposure, so as to establish the true burden of disease. Since the recognition in April 2003 of the severe acute respiratory syndrome coronavirus (SARS-CoV) as the causative agent of severe acute respiratory syndrome (SARS), enormous efforts have been applied to develop molecular and serological tests for SARS which can assist rapid detection of cases, accurate diagnosis of illness and the application of control measures. International progress in the laboratory diagnosis of SARS-CoV infection during acute illness has led to internationally agreed World Health Organization criteria for the confirmation of SARS. Developments in the dissection of the human immune response to SARS indicate that serological tests on convalescent sera are essential to confirm SARS infection, given the sub-optimal predictive value of molecular detection tests performed during acute SARS illness.     

Hunter syndrome: prenatal diagnosis in maternal serum.

Iduronate sulfate sulfatase (ISS), the deficient hydrolase in Hunter syndrome, consistently increases in the serum of pregnant women, reaching a three- to fourfold increase from pre-pregnancy levels toward the end of pregnancy. In Hunter carriers, a correlation occurs between the status of the fetus with regard to Hunter syndrome and the ISS increase in maternal serum. Thus, in pregnancies with Hunter-affected fetuses, enzyme levels did not change in the serum of heterozygous mothers until abortion was performed, while in nonaffected fetuses, ISS increased usually very early in pregnancy--as early as the 6th-12th week. In heterozygote female fetuses, this increase might be delayed. These data imply that a prenatal diagnosis of Hunter syndrome might be accomplished in maternal serum at early conventional procedures for the prenatal diagnosis of Hunter syndrome.     

Rett syndrome molecular diagnosis and implications in genetic counseling

Rett syndrome is a rare genetic X-linked dominant disorder. This syndrome is the most frequent cause of mental retardation in girls. In the classical form of the disease, the presenting signs and the course of development are characteristic. However clinical diagnosis can be very difficult when the expression is not in the classical form. Mutations in MeCP2 are responsible for 80% of cases. When MeCP2 mutation is found in an index case, genetic counseling is similar to that in other X-linked dominant genetic diseases. However, mutations in this gene can cause a spectrum of atypical forms. On the other hand, other genetic conditions like translocations, sex chromosome numerical anomalies, and mutations in other genes can complicate genetic counseling in this syndrome. We present the first case of molecular diagnosis of Rett syndrome in Iran and discuss the recent developments in its genetic counseling.     

Linkage analysis for prenatal diagnosis in a familial case of Stickler syndrome

The Stickler syndrome is among the most common heritable disorders of connective tissue. The syndrome fully expressed clinical phenotype includes the degeneration of the vitreous gel and retina, frequently associated with myopia, accompanied by non-ocular features, such as craniofacial dysmorphisms or malformations, hearing impairment, skeletal dysplasia and progressive arthropathy. So far, mutations at three collagen loci, COL2A1, COL11A1 and COL11A2, have been found in Stickler syndrome patients, with about two thirds of investigated familial cases found to be associated to COL2A1 gene mutations. We report on a three generation family in which a diagnosis of Stickler syndrome was made and linkage analysis suggested COL2A1 to be the causing gene. These data permitted us to perform two prenatal diagnosis analysing the 3'VNTR polymorphism of the involved gene on amniocytes' DNA and to provide the family with genetic counselling and paediatric support at the delivery.     

Prenatal diagnosis of Meckel syndrome

Summary The three main features of Meckel syndrome are encephalocele, polycystic kidneys, and polydactyly. Prenatal diagnosis of a fetus with Meckel syndrome was made in the 16th week of gestation by means of amniotic fluid alpha₁ fetoprotein estimation. The indication for amniocentesis was a previous child with an occipital meningocele and polycystic kidneys. Interpretation of the alpha₁-fetoprotein value (240 g/ml) was difficult due to fetal blood contamination. Prenatal diagnosis is indicated in any pregnancy following the birth of a child with only two major symptoms of Meckel syndrome.     

Problems posed by prenatal diagnosis of abdominal wall malformations

The authors present 6 observations of in utero detected abdominal wall defect : 2 laparoschisis and 4 omphaloceles. In three cases the diagnosis have been done prior week 20, by systematic AFP assay for amniocentesis performed for cytogenetic or metabolic reasons; the pregnancy was terminated. In three other cases, the pregnancy was complicated by hydramnios after week 30; amniocentesis for AFP and echography were performed to detect fetal malformations after associated with hydramnios. The detected abdominal wall anomaly was not alone: two fetus had an abnormal caryotype (trisomy 18), three other presented a polymalformative syndrome, a Beckwith-Wiedemann syndrome was discussed for the last child. The in utero diagnosis of omphalocele or laparoschisis implicates difficulties for genetic counselling, particularly if the diagnosis is done prior week 20. These anomalies can be treated with surgical management, but frequency of associated malformations must be underlined. it is important for genetic counselling to know the family history, the amniotic fluid cells caryotype, and an ultrasound scanning performed to reveal any other malformations.     

Prenatal ultrasonographic diagnosis of a recurrent case of Johanson-Blizzard syndrome

We report on ultrasonographic prenatal diagnosis of a recurrent case of Johanson-Blizzard syndrome. The pregnancy was terminated at 21 weeks'. This observation highlights the great variability of the expression of this syndrome, including in the same family, and the necessity of collaborating with an experienced geneticist in all antenatal diagnosis of any complex of abnormalities.     

Simple diagnosis of the Zellweger syndrome by gas-liquid chromatography of dimethylacetals

The absence of peroxisomes in patients with the cerebrohepatorenal syndrome of Zellweger leads to several biochemical abnormalities, including deficient synthesis of plasmalogens as well as accumulation of very long-chain fatty acids and intermediates in bile acid biosynthesis. Accumulation of very long-chain fatty acids in serum and fibroblasts has hitherto been used most extensively for diagnosis. Due to the relatively small amounts of the very long-chain fatty acids also in the Zellweger patients, and the risk for interfering impurities, such analyses are difficult. Direct assay of plasmalogens is also relatively difficult and time-consuming. In this report, we describe a relatively simple method for diagnosis, based on gas-liquid chromatography of a lipid extract of erythrocytes after methyl transesterification. The alpha, beta-unsaturated ether in the plasmalogen is converted to the dimethylacetal of the corresponding aldehyde, and the relative amount of plasmalogen is thus reflected by the ratio between 18:0 dimethylacetal and methyl stearate as well as by the ratio between 16:0 dimethylacetal and methyl palmitate. The ratio 18:0 dimethylacetal/methyl stearate was found to be 0.28 +/- 0.03 (mean +/- SD) after analyses of erythrocytes from healthy or non-Zellweger infants, but less than 0.02 in erythrocytes from three infants with the Zellweger syndrome. Preliminary work with amniotic fluid suggests that this analysis may be suitable also for prenatal diagnosis of the Zellweger syndrome.     

Prenatal diagnosis of trisomy 9.

A male karyotype with trisomy 9 (47,XY,+9) was identified in amniotic fluid cells from a 40-year-old pregnant woman. After termination of the pregnancy by saline abortion, the cytogenetic diagnosis was confirmed in a cell line grown from placental tissue. Microscopic and gross pathological findings in the fetus were compared to 1 case with trisomy 9 and 3 with trisomy 9 mosaicism reported in the literature. A distinct clinical syndrome appears to be associated with this rare autosomal trisomy.     

Molecular diagnosis of bilateral coronal synostosis.

The authors performed a prospective study evaluating molecular diagnosis in patients with bilateral coronal synostosis. The patients were divided into two groups: (1) those clinically classified as having Apert, Crouzon, or Pfeiffer syndrome and (2) those clinically unclassified and labeled as having brachycephaly. Blood samples were drawn for genomic DNA analysis from 57 patients from 1995 to 1997. Polymerase chain reactions were performed using primers flanking exons in FGFR 1, 2, and 3. Each exon was screened for mutations using single-strand confirmation polymorphism, and mutations were identified by DNA sequencing. Mutations in FGFR2 or FGFR3 were found in all patients (n = 38) assigned a phenotypic (eponymous) diagnosis. All Apert syndrome patients (n = 13) carried one of the two known point mutations in exon 7 of FGFR2 (Ser252Trp and Pro253Arg). Twenty-five patients were diagnosed as having either Crouzon or Pfeiffer syndrome. Five patients with Crouzon syndrome of variable severity had mutations in exon 7 of FGFR2. Fifteen patients (12 with Crouzon, 3 with Pfeiffer) had a mutation in exon 9 of FGFR2, many of which involved loss or gain of a cysteine residue. A wide phenotypic range was observed in patients with identical mutations, including those involving cysteine. Two patients labeled as having Crouzon syndrome had the Pro250Arg mutation in exon 7 of FGFR3. All three patients with the crouzonoid phenotype and acanthosis nigricans had the same mutation in exon 10 of FGFR3 (Ala391Glu). This is a distinct disorder, characterized by jugular foraminal stenosis, Chiari I anomaly, and intracranial venous hypertension. Mutations were found in 14 of 19 clinically unclassifiable patients. Three mutations were in exon 9, and one was in the donor splice site of intron 9 on FGFR2. The most common mutation discovered in this group was Pro250Arg in exon 7 of FGFR3. These patients (n = 10) had either bilateral or unilateral coronal synostosis, minimal midfacial hypoplasia with class I or class II occlusion, and minor brachysyndactyly. No mutations in FGFR 1, 2, or 3 were detected in five patients with nonspecific brachycephaly. In conclusion, a molecular diagnosis was possible in all patients (n = 38) given a phenotypic (eponymous) diagnosis. Different phenotypes observed with identical mutations probably resulted from modulation by their genetic background. A molecular diagnosis was made in 74 percent of the 19 unclassified patients in this series; all mutations were in FGFR2 or FGFR3. Our data and those of other investigators suggest that we should begin integrating molecular diagnosis with phenotypic diagnosis of craniosynostoses in studies of natural history and dysmorphology and in analyses of surgical results.     

Patterns of retinal damage facilitate differential diagnosis between Susac syndrome and MS

Susac syndrome, a rare but probably underdiagnosed combination of encephalopathy, hearing loss, and visual deficits due to branch retinal artery occlusion of unknown aetiology has to be considered as differential diagnosis in various conditions. Particularly, differentiation from multiple sclerosis is often challenging since both clinical presentation and diagnostic findings may overlap. Optical coherence tomography is a powerful and easy to perform diagnostic tool to analyse the morphological integrity of retinal structures and is increasingly established to depict characteristic patterns of retinal pathology in multiple sclerosis. Against this background we hypothesised that differential patterns of retinal pathology facilitate a reliable differentiation between Susac syndrome and multiple sclerosis. In this multicenter cross-sectional observational study optical coherence tomography was performed in nine patients with a definite diagnosis of Susac syndrome. Data were compared with age-, sex-, and disease duration-matched relapsing remitting multiple sclerosis patients with and without a history of optic neuritis, and with healthy controls. Using generalised estimating equation models, Susac patients showed a significant reduction in either or both retinal nerve fibre layer thickness and total macular volume in comparison to both healthy controls and relapsing remitting multiple sclerosis patients. However, in contrast to the multiple sclerosis patients this reduction was not distributed over the entire scanning area but showed a distinct sectorial loss especially in the macular measurements. We therefore conclude that patients with Susac syndrome show distinct abnormalities in optical coherence tomography in comparison to multiple sclerosis patients. These findings recommend optical coherence tomography as a promising tool for differentiating Susac syndrome from MS.     

Incomplete EcoRI digestion may lead to false diagnosis of fragile X syndrome

Molecular diagnosis of fragile X syndrome is usually performed using Southern blot analysis of DNA digested with EcoRI. In the course of diagnostic studies, we observed that a specific EcoRI restriction site in the fragile X gene (FMR1) is sometimes refractory to digestion, generating additional fragments on a Southern blot suggestive of a full mutation in FMR1. This may lead to a false-positive diagnosis of fragile X syndrome. Such additional bands are avoided by the use of HindIII instead of EcoRI. Therefore, we recommend the use of HindIII for the molecular diagnosis of fragile X syndrome. Received: 11 September 1997 / Accepted: 25 September 1997     

The diagnosis of HPRT deficiency in the 21st century

We have studied 36 patients with HPRT deficiency, 25 with Lesch-Nyhan syndrome and 11 with partial HPRT deficiency (grades 1 to 3). Patients diagnosed with HPRT deficiency have increased 50% since 2000. The most relevant recent advances have been made in molecular diagnosis. Nevertheless, enzyme determinations are still essential for the diagnosis of HPRT deficiency. Therapy for the neurological manifestations of HPRT deficiency has not advanced. Allopurinol remains the drug of choice to diminish uric acid overproduction, but the optimal allopurinol dose must be established in each patient to prevent xanthine or uric acid urolithiasis, a process aided by sequential determination of urinary oxypurines and uric acid.     

Genetic heterogeneity and pathology of congenital nephrotic syndrome and its significance in prenatal diagnosis

Familial occurrence of congenital nephrotic syndrome (CN) has been most extensively studied in Finland where it is known to be inherited as an autosomal recessive disease. In this Finnish type of congenital nephrotic syndrome (CNF) prenatal diagnosis by alphafetoprotein (AFP) determination in the amniotic fluid has been reported to be conclusive. Within the last six years we observed 10 cases of CN occurring in 5 families. In all patients renal histology has been studied. Although each family presented a different type of CN, the appearance within the same sibship was always identical.     

Test of a new technique for the diagnosis of carpal tunnel syndrome.

Several new techniques for carpal tunnel syndrome diagnosis have been developed in the last few years. This work tests a technique that compares the distal motor latency of the median nerve to the second lumbrical muscle (2L) with the distal motor latency of the ulnar nerve to the interossei muscle (INT). Results from 40 normal hands give the superior limit of the normal difference (2L-INT) as 0. 26 ms (&xmacr;+3 SD). In 55 hands with different levels of carpal tunnel syndrome, this new technique was more sensitive and accurate than the conventional test which uses the distal motor latency of the median nerve to the abductor pollicis brevis muscle (APB), especially in the less severe cases. With the absence of the compound muscle action potentials of the APB muscle caused by severe thenar atrophy, it is much easier to obtain the potential from the 2L muscle. We concluded that this is a sensitive, simple, rapid, and non-invasive new technique, and therefore, it should be incorporated as part of the routine ENMG procedures for carpal tunnel syndrome diagnosis.     

Towards a more rapid diagnosis of rapidly progressive glomerulonephritis.

An attempt was made to provide simple practical guidelines to alert general practitioners to the diagnosis of rapidly progressive glomerulonephritis and lead to early referral to hospital. The duration of illness before referral to this hospital and its effect on outcome in patients with crescentic nephritis were assessed retrospectively from the case notes of 24 patients referred over two years. Four patients had Goodpasture''s syndrome, 11 Wegener''s granulomatosis, seven microscopic polyarteritis, and two idiopathic progressive glomerulonephritis. The duration of symptoms before referral to the local hospital was similar in the four groups of patients and varied from one week to 28 months (mean 10 months). The duration of stay in the local hospital was two, nine, 11, and 180 days in the patients with Goodpasture''s syndrome and a mean of four days (range one to eight) in those with Wegener''s granulomatosis and 10 days (one to 18 days) in those with microscopic polyarteritis. In the local hospital the diagnosis was based on the results of renal biopsy and detection of antibodies to glomerular basement membrane in two patients with Goodpasture''s syndrome and on the results of renal biopsy in seven of the other patients aided by the detection of antibodies to the cytoplasm of neutrophils (ANCA) in 10. Three of the 24 patients died and four required maintenance haemodialysis. Patients who present to their general practitioners with persistent non-specific symptoms should have a urine dipstick test and then blood tests and emergency referral to hospital if necessary. Hospital physicians should be aware of the speed and accuracy with which current assays can confirm a diagnosis of rapidly progressive glomerulonephritis.     

Bloom's syndrome. Discussion of the diagnosis concerning two cases of terminal leukemia in a sibship (author's transl)

Two brothers developed acute leukemia, one at the age of 7 months and the other at the age of 14 months. Both suffered from a staturoponderal retardation and the same malformation syndrome. The karyotype carried out only on the second child revealed breaks and chromatid changes. A diagnosis of Fanconi's anaemia can be discarbed since no blood cytopenia preceded the leukemia. Finally, the diagnosis of Bloom's syndrome prevailed despite the absence of telangiectatic erythema and the atypical chromosomal anomalies.     

Etiology, pathogenesis, and diagnosis of interstitial cystitis

Interstitial cystitis (IC) is a bladder syndrome of unknown etiology. The cause of IC is most likely multifactorial and includes genetic and environmental factors. Various pathophysiological changes in the bladder, pelvis, and peripheral and central nervous systems have been identified, and this has led to the emergence of biologically specific treatment modalities. Interstitial cystitis is being diagnosed with increasing frequency; however, current diagnostic criteria are non-uniform, and there is significant overlap between chronic pelvic pain syndromes in men and women, interstitial cystitis, recurrent "cystitis," and the overactive bladder syndrome. The diagnosis of interstitial cystitis can be made clinically and by cystoscopy and hydrodistension. The sensitivity and specificity of urinary markers and the potassium sensitivity test have not been prospectively studied.     

A case of Kartagener's syndrome: Importance of early diagnosis and treatment

Kartagener''s syndrome is a very rare congenital malformation comprising of a classic triad of sinusitis, situs inversus and bronchiectasis. Primary ciliary dyskinesia is a genetic disorder with manifestations present from early life and this distinguishes it from acquired mucociliary disorders. Approximately one half of patients with primary ciliary dyskinesia have situs inversus and, thus are having Kartagener syndrome. We present a case of 12 year old boy with sinusitis, situs inversus and bronchiectasis. The correct diagnosis of this rare congenital autosomal recessive disorder in early life is important in the overall prognosis of the syndrome, as many of the complications can be prevented if timely management is instituted, as was done in this in this case.