Diagnostic power and clinical impact of exome sequencing in a cohort of 500 patients with rare diseases.

Rare diseases comprise a diverse group of conditions, most of which involve genetic causes. We describe the variable spectrum of findings and clinical impacts of exome sequencing (ES) in a cohort of 500 patients with rare diseases. In total, 164 primary findings were reported in 158 patients, representing an overall diagnostic yield of 31.6%. Most of the findings (61.6%) corresponded to autosomal dominant conditions, followed by autosomal recessive (25.6%) and X-linked (12.8%) conditions. These patients harbored 195 variants, among which 43.6% are novel in the literature. The rate of molecular diagnosis was considerably higher for prenatal samples (67%; 4/6), younger children (44%; 24/55), consanguinity (50%; 3/6), gastrointestinal/liver disease (44%; 16/36) and syndromic/malformative conditions (41%; 72/175). For 15.6% of the cohort patients, we observed a direct potential for the redirection of care with targeted therapy, tumor screening, medication adjustment and monitoring for disease-specific complications. Secondary findings were reported in 37 patients (7.4%). Based on cost-effectiveness studies in the literature, we speculate that the reports of secondary findings may influence an increase of 123.2 years in the life expectancy for our cohort, or 0.246 years/cohort patient. ES is a powerful method to identify the molecular bases of monogenic disorders and redirect clinical care.

When karyotype is decisive for myelodysplastic syndromes diagnosis

ABSTRACT Introduction: The myelodysplastic syndromes (MDS) are a group of heterogeneous clonal hematopoietic stem cell disorders that results in peripheral blood (PB) cytopenias and bone marrow (BM) dysplasia. Dysplasia is the hallmark of the disorder, and must exceed the threshold of 10%. Conventional karyotype (KT) has a role in the classification and prognostication of subtypes. In daily practice, many cases are diagnosed in face of exuberant clinical complains, but cases with dismal evidences pose real difficulties to definitively conclude the case. Material and methods: The objective of this study is to detect cases in which no morphology evidence of dysplasia or increased blasts were observed but KT was decisive for MDS diagnosis. 666 cases were admitted to rule out MDS. Results: There were found 5 (0.75%) cases who presented no evident dysplasia morphology or whose dysplasia was borderline but the karyotype was decisive because showed clonal evidence. The karyotype was: case 1: 46,XY,del(5q)(q13q33),del(11)(q13q23)[7]/46,XY[13]; case 2: 46,XX,del(11)(q21q23)[20]; case 3: 46,XX,del(7)(q22q34)[4]/46,XX[8]; case 4: 47,XX,del(5)(q13q33),+mar[12]/46,XX[8] and case 5: 46,XXt(2;11)(p21;q24),del(4)(?q25),del(21)(q22)[14]/46,XX[6]. Conclusion: Patients with cytopenia and insufficient or borderline evidence of dysplasia may experience a long journey before a MDS diagnosis is made. Cytogenetics studies may abbreviate this pathway when clonal aberrations considered presumptive of MDS are detected. This study shows that karyotype should still be considered as a diagnostic tool.

When karyotype is decisive for myelodysplastic syndromes diagnosis.

INTRODUCTION: The myelodysplastic syndromes (MDS) are a group of heterogeneous clonal hematopoietic stem cell disorders that results in peripheral blood (PB) cytopenias and bone marrow (BM) dysplasia. Dysplasia is the hallmark of the disorder, and must exceed the threshold of 10%. Conventional karyotype (KT) has a role in the classification and prognostication of subtypes. In daily practice, many cases are diagnosed in face of exuberant clinical complains, but cases with dismal evidences pose real difficulties to definitively conclude the case. MATERIAL AND METHODS: The objective of this study is to detect cases in which no morphology evidence of dysplasia or increased blasts were observed but KT was decisive for MDS diagnosis. 666 cases were admitted to rule out MDS. RESULTS: There were found 5 (0.75%) cases who presented no evident dysplasia morphology or whose dysplasia was borderline but the karyotype was decisive because showed clonal evidence. The karyotype was: case 1: 46,XY,del(5q)(q13q33),del(11)(q13q23)[7]/46,XY[13]; case 2: 46,XX,del(11)(q21q23)[20]; case 3: 46,XX,del(7)(q22q34)[4]/46,XX[8]; case 4: 47,XX,del(5)(q13q33),+mar[12]/46,XX[8] and case 5: 46,XXt(2;11)(p21;q24),del(4)(?q25),del(21)(q22)[14]/46,XX[6]. CONCLUSION: Patients with cytopenia and insufficient or borderline evidence of dysplasia may experience a long journey before a MDS diagnosis is made. Cytogenetics studies may abbreviate this pathway when clonal aberrations considered presumptive of MDS are detected. This study shows that karyotype should still be considered as a diagnostic tool.