Prenatal Diagnosis of Pompe Disease – Enzyme Assay or Molecular Testing.

We report two cases which illustrate that enzyme assay results alone, may at times be equivocal and inconclusive in the prenatal diagnosis of storage disorders like Pompe disease and therefore, if the proband’s mutation is known, targeted mutation analysis of fetal DNA is the most reliable method for fetal evaluation.

Recombinant Macrophage Targeted Enzyme Replacement Therapy for Gaucher Disease in India.

Objective: Gaucher disease in India has been reported only in a few case reports from India. The aim of the study was to assess the response to enzyme replacement therapy in Indian patients with Gaucher disease. Design: Retrospective analysis of patients receiving CHO-derived recombinant macrophage-targetted glucocorebrosidase. Setting: Five centers from India with experience in treating lysosomal storage disorders. Patients: The diagnosis of Gaucher disease was confirmed by low glucocerebrosidase levels, though it was first made on splenectomy in 8 and on bone marrow examination in 9 patients. Twenty five of 52 patients diagnosed with Gaucher disease (17 Type I, 8 mild Type III) received treatment for >6 months. Indications for treatment included symptomatic anemia, thrombocytopenia, organomegaly, bone disease or mild neurological symptoms leading to impairment of quality of life. Patients with significant neurological involvement were excluded. The drug infusions were given intravenously every 15 days. Main Outcome measures: Hemoglobin, platelet counts, liver and spleen volumes and growth parameters. Results: 22 of the 25 children who survived were analyzed. After 6 months of treatment, the mean (range) increase in hemoglobin was 1.5 (-3.4 to 6.1) g/dL (P=0.01) and in platelet count was 32 x 109/L (-98.5 x 109 to 145.5 x109) /L (P=0.02). The mean (range) increase in weight was 3 kg (-5.6 to 10.5) (P=0.04) and in height was 7.1 cm (0 to 26.5) (P=0.0003). Liver size decreased by a mean (range) of 38.5% (- 5.5 to 86.7) (P=0.0003) and the spleen size by 34.8% (0 to 91.7) (P=0.004). All patients had improvement in bone pains and in 2 patients, neurological symptoms improved with others remaining static. Conclusions: This is the first reported cohort of patients in India reporting our experience with imiglucerase enzyme replacement therapy for treatment of Gaucher Disease in India.

Mutation analysis in Indian children with achondroplasia - utility of molecular diagnosis.

OBJECTIVE: Mutation analysis in Indian children with achondroplasia. METHODS: We studied 11 sporadic cases of achondroplasia. Mutation analysis was done by PCR/RFLP (Polymerase chain reaction/Restriction fragment length polymorphism) method. RESULTS: Nine of the 11 cases had mutation G-->A at 1138 nucleotide position in transmembrane domain of fibroblast growth-factor receptor 3 (FGFR3) gene. Substitution G-->A is a common recurrent mutation reported worldwide. In two cases we could not detect any common mutation and also in entire region of transmembrane domain sequenced. There is possibility of mutation in the other regions of FGFR3 gene in these two cases. CONCLUSION: Further study of these two cases is needed in order to define other genotypes resulting in achondroplasia. Postnatal diagnosis of achondroplasia depends on clinical and radiological features. Mutation detection is mainly useful for prenatal diagnosis.

Molecular diagnosis and genetic counseling for fragile X mental retardation.

The fragile X syndrome is the most frequent cause of inherited mental retardation. It is caused by a dynamic mutation: the progressive expansion of polymorphic (CGG)n trinucleotide repeats located in the promoter region of the FMRI gene at Xq27.3. The cloning of the FMRI gene and the elucidation of the molecular basis of the fragile X syndrome is of great importance for the diagnosis and understanding of this unusual type of mutation. Although extensively studied, the mechanism behind the transition from stable normal (CGG)n alleles to the carrier state (an unstable premutation) and from premutation to mutation is partially understood. The clinical diagnosis of fragile X mental retardation (FXMR) is not possible as dysmorphic features are subtle. Molecular diagnosis by Southern Blot is the confirmatory test that makes carrier detection and prenatal diagnosis possible. As the risk of recurrence of FXMR is high in the family and carrier relatives, an identification of fragile X positive children, and offering carrier detection and prenatal diagnosis to the families is very important. It is possible by screening mentally retarded children and adults even if there is no family history of mental retardation or typical behavioral or physical features associated with the fragile X phenotype. In this review we have discussed the method for the diagnosis and counseling of the families. The complexities due to premutation and the variable severity of manifestations in carrier females need to be understood while counseling fragile X families.

Connexin 26 and autosomal recessive non-syndromic hearing loss.

Prelingual deafness occurs with a frequency of 1 in 1000 live births and is divided into syndromic and non-syndromic forms contributing 40 and 60% respectively. Autosomal recessive non-syndromic hearing loss (ARNSHL) is responsible for 80% cases of childhood deafness. Nearly all genes localized for ARNSHL cause prelingual, severe to profound, sensorineural hearing impairment. ARNSHL is genetically heterogeneous and at least 39 loci have been identified. The most significant finding to date has been the discovery of mutations in GJB2 gene at the DFNB1 locus on chromosome 13q12 as the major cause of profound prelingual deafness. This was first reported in a Tunisian family in 1994 and thereafter in many different countries. GJB2 gene encodes the gap-junction protein, connexin 26 (Cx26), mutations in which have become the first genetic marker of inherited hearing loss. Allele-specific polymerase chain reaction (AS-PCR), single stranded conformation polymorphism (SSCP) and sequencing methods have been developed for the detection of mutations in Cx26 gene. In India as well, the Cx26 mutations are being screened in families with hearing impaired children using these molecular methods. Therefore, in order to create awareness among the clinicians and the affected families; we have attempted to review the Cx26 gene mutations responsible for autosomal recessive type of non-syndromic hearing loss. The efficacy and utility of Cx26 gene analysis might open the path to proper counseling of families for carrier detection and prenatal diagnosis. It may even facilitate the development of strategies in future for the treatment of this common genetic disorder.

Low level of mosaicism in atypical Prader Willi syndrome: detection using fluorescent in situ hybridization.

Prader Willi syndrome (PWS) most commonly is due to paternal micro-deletion of 15q11-q13. Although PWS is not a rare condition, mosaic micro-deletion cases are reported rarely. FISH using PWS micro-deletion probe is the most useful method to detect deletion including mosaicism. In this report we describe a female child with clinical features of atypical PWS and FISH analysis showing mosaicism for deletion in the PWS critical region. This is first mosaic deletion case of PWS from Indian subcontinent.

Internet resources for hemato-oncologist.

AIM OF THE STUDY: To find out sites of interest for the hemato-oncologist on the internet. METHODOLOGY: Use of search engines like www.google.com and www.yahoo.com and selective identification of the relevant sites by thorough browsing. RESULTS: There are several sites which can be useful to the hemato-oncologist. Some of the sites are related to hematology, hemato-oncology, hemato-pathology, etc. were as some are disease specific e.g., thalassemia, hemophilia, myelodysplastic syndrome. Reliability of the sites have to be judged carefully. CONCLUSIONS: Certain sites provide specific information for selected diseases, and accordingly online browsing is required. Latest articles can be retrieved from Pubmed, Biomednet (www.bmn.com) and few general haematology sites like www.medweb.emory.edu and the cancer-related site www.aacr.org. The benefits of internet include rapid access to relevant information, easy use and also e-consultations.

Clinical profile of hereditary spherocytosis in North India.

AIMS OF THE STUDY: Hereditary spherocytosis (HS) is a familial hemolytic disorder manifesting as anaemia, recurrent jaundice, splenomegaly with marked heterogeneity in clinical presentation. The objective was to study the clinical spectrum of the disorder in India. METHODOLOGY: We studied 50 HS patients and followed them for up to six years (Age range 2-47 years). RESULTS: The presenting features were jaundice 35 out of 50, anaemia 30 out of 50 (requiring blood transfusion in 25). Splenomegaly was found in all patients. Increased osmotic fragility was found in all patients whereas spherocytes were found in only 19 out of 42 patients. Reduced red cell survival was noted in 9/12 patients studied with 51Cr labeled RBCs. There was a definite improvement in the hemoglobin values in those who underwent splenectomy. Thirteen cases had similarly affected family member/s. Fifteen of the cases had family history consistent with autosomal dominant (AD) inheritance (eight families) while in six cases (5 families), inheritance was likely to be autosomal recessive (AR). There was intrafamilial variability in the age of presentation in the AD families. CONCLUSIONS: Our results suggest that both autosomal dominant and recessive patterns of HS are seen in India and the clinical profile of the Indian HS patients is similar to that described in other populations. HS presenting in childhood is also not uncommon. However, the predominant underlying protein defect in Indian patients needs to be characterized.

Clinical and molecular diagnosis of spinal muscular atrophy.

The spinal muscular atrophies are a group of disorders characterized by flaccid limb weakness. It is necessary to differentiate these from other causes and identify the SMA variants. In classical SMA, majority of the patients shows homozygous deletion of the telomeric SMN gene (SMN1) on chromosome 5q. The availability of DNA analysis has allowed proper genetic counseling and prenatal diagnosis in the affected families. Application of newer techniques has enabled more accurate carrier detection. Our objective is to stress the variability in the clinical features and recent advances in the molecular diagnosis for SMA.

Carrier detection in non-deletional Duchenne/Becker muscular dystrophy families using polymorphic dinucleotide (CA) repeat loci of dystrophin gene.

BACKGROUND & OBJECTIVES: Carrier detection and prenatal diagnosis is of great importance for families with one or more sons affected with Duchenne/Becker muscular dystrophy (D/BMD). In about 35-40 per cent of these patients, the causative mutation does not involve gross rearrangement in the structure of dystrophin gene. In these non-deletional families, genetic counselling can be provided only by linkage analysis. The aim of the present study was to determine the carrier status of female relatives in north Indian families with non-deletional D/BMD using highly polymorphic intragenic dinucleotide (CA) repeat markers. METHODS: Six short tandem repeats (STRs) spanning 5' (1), central (4) and 3' regions of the dystrophin gene were used to analyse 14 unrelated families comprising 68 individuals with 12 female siblings at risk of being carriers. RESULTS: Five female siblings inherited at risk STR haplotype, six inherited normal haplotype and one had meiotic recombination. The intragenic recombinations were observed in three families at the central region STR loci and in one family between the proximal and central regions of the gene. INTERPRETATION & CONCLUSIONS: Our study suggested that at least 6 STR markers spanning 5', central and 3' regions of the dystrophin gene are essential to ascertain one or more informative loci and to rule out recombinations in non-deletional D/BMD families for carrier analysis.

Linear catch-up growth.

Chronic diseases and malnutrition cause growth failure in childhood and adolescence. Correction of the cause of a growth deficiency is usually followed by catch-up growth. Capacity to catch-up is not only variable in different phases of growth, it is also different in different diseases and among different individuals suffering from the same disease. Catch-up growth is of three types. In type 1 catch-up growth, height deficit is swiftly eliminated after the growth restriction ceases. In type 2, after growth restriction ceases growth continues for longer than usual and growth arrest is compensated. Type 3 is a mixture of type 1 and type 2. Repeated episodes of growth inhibitory conditions result in lower catch-up rates in the subsequent periods. Although the exact mechanism regulating catch-up growth still remains a mystery, monitoring catch-up growth remains an important measure of the efficacy of the therapy and therefore of immense clinical importance.

Mandibulo-acral dysplasia: Indian patient with severe bony changes.

We report an Indian patient with mandibulo-acral dysplasia. This patient had absence of spinous processes of 4th and 5th cervical vertebrae and very severe bony changes but no loss of teeth.

Does autopsy of antenatally diagnosed malformed foetuses aid genetic counselling?

BACKGROUND: Many pregnancies are terminated because of ultrasonographic diagnosis of malformation in the foetus. A detailed foetal autopsy is needed to arrive at a definite diagnosis on the basis of which genetic counselling can be provided. METHODS: Sixty-one foetuses, terminated because of antenatal diagnosis of congenital malformations by ultrasound, were autopsied. The ultrasound diagnosis was compared with the diagnosis reached after autopsy. RESULTS: In 31 cases (51%) the autopsy provided additional findings. In 21 cases (34.4%), the autopsy changed the primary diagnosis. The revised diagnosis led to a change in the risk of recurrence in 18 cases (29.5%). CONCLUSION: Genetic counselling depending solely on ultrasonographic foetal diagnosis may be erroneous. For appropriate genetic counselling, a detailed foetal examination should be carried out after termination in cases with ultrasonographically detected congenital malformations.