Clinical analysis of families with heart, midline, and laterality defects

Disturbances of the normal asymmetric placement of organs, such as polysplenia or situs inversus, have been defined traditionally as laterality defects. However, there is compelling evidence from vertebrate models and human birth defects to hypothesize that defects of the midline, isolated congenital heart defects, and laterality defects are etiologically related. We present the clinical characteristics of three families that exhibit a variety of midline defects and isolated heart defects in addition to laterality defects. These observations suggest that the phenotypic consequences of mutations causing laterality defects include defects of the midline as well as isolated heart defects. To further explore the relationship between midline, heart, and laterality defects, it is imperative that detailed phenotyping of individuals and families with laterality defects be done and a classification system created to facilitate identification of genes causing human laterality disorders.     

Autosomal dominant transmission of familial laterality defects

Heterotaxy results from failure to establish normal left-right asymmetry during embryonic development. Most familial cases are thought to be autosomal recessive. We have identified a family in which 4 individuals from 3 generations manifest laterality defects. Twenty-five family members have been examined. Two have complete reversal of normal laterality (situs inversus) while 2 others have asplenia, midline liver, and complex cardiac malformations (situs ambiguus). Two additional obligate gene carriers are anatomically normal (situs solitus). Male-to-male transmission confirms autosomal inheritance. Identification of this family establishes an autosomal dominant form of laterality defect, suggesting that a portion of sporadic cases may be new-mutation dominant or unrecognized familial cases. The finding of all forms of laterality (solitus, ambiguus, and inversus) among obligate disease gene carriers within a single family may be relevant to genetic evaluation and counseling in apparently isolated patients with laterality disturbance. © 1996 Wiley-Liss, Inc.     

X-linked laterality sequence: situs inversus, complex cardiac defects, splenic defects

The association of abdominal situs inversus, complex cardiac defects, and alterations in development of the spleen represents a developmental field complex with variable expression of altered laterality. Familial and inherited cases documenting respectively autosomal recessive and dominant inheritance have been reported. We report on the first family in which X-linked recessive inheritance of this defect has been documented.     

Exome sequencing in individuals with cardiovascular laterality defects identifies potential candidate genes

The birth prevalence of laterality defects is about 1.1/10,000 comprising different phenotypes ranging from situs inversus totalis to heterotaxy, mostly associated with complex congenital heart defects (CHD) and situs abnormalities such as intestinal malrotation, biliary atresia, asplenia, or polysplenia. A proportion of laterality defects arise in the context of primary ciliary dyskinesia (PCD) accompanied by respiratory symptoms or infertility. In this study, exome sequencing (ES) was performed in 14 case-parent trios/quattros with clinical exclusion of PCD prior to analysis. Moreover, all cases and parents underwent detailed clinical phenotyping including physical examination, echocardiography by a skilled paediatric cardiologist and abdominal ultrasound examinations not to miss mildly affected individuals. Subsequent survey of the exome data comprised filtering for monoallelic de novo, rare biallelic, and X-linked recessive variants. In two families, rare variants of uncertain significance (VUS) in PKD1L1 and ZIC3 were identified. Both genes have been associated with laterality defects. In two of the remaining families, biallelic variants in LMBRD1 and DNAH17, respectively, were prioritized. In another family, an ultra-rare de novo variant in WDR47 was found. Extensive exome survey of 2,109 single exomes of individuals with situs inversus totalis, heterotaxy, or isolated CHD identified two individuals with novel monoallelic variants in WDR47, but no further individuals with biallelic variants in DNAH17 or LMBRD1. Overall, ES of 14 case-parent trios/quattros with cardiovascular laterality defects identified rare VUS in two families in known disease-associated genes PKD1L1 and ZIC3 and suggests DNAH17, LMBRD1, and WDR47 as potential genes involved in laterality defects.Subject terms: Disease genetics, Genetic counselling, Biological sciences     

Clinical aspects of the complement system

The complement system consists of more than 30 proteins and has 3 types of activation pathways: classical, lectin and alternative pathways. The complement system not only has a role in innate immunity but also works as an antibody-dependent effecter to eliminate pathogens. It is useful to measure serum levels of CH50, C3 and C4 in patients with immune-mediated diseases. While increased levels of CH50 are associated with non-specific inflammation, decreased levels of CH50 in combination with normal or decreased levels of C3 and C4 are associated with specific immune-mediated diseases. Recent studies have demonstrated that the defect in the clearance of immune complexes and apoptotic cells is associated with autoimmune disease. Mice deficient in Clq show a lupus-like phenotype with the appearance of antinuclear antibodies and glomerulonephritis due to a defect in the clearance of immune complexes and apoptotic cells. This at least explains the paradox that, in humans, deficiency in an early complement component is a major risk factor for SLE. It is demonstrated that mutations in factor H, membrane cofactor protein (MCP) and factor I gene are associated with atypical hemolytic uremic syndrome. Since the complement system is a central mediator of inflammation, it is recognized as a promising therapeutic target. Anti-C5 monoclonal antibody was developed to block the final stage of complement activation. Pexelizumab is a single chain, short-acting anti-C5 antibody and is used for reperfusion after myocardial infarction, or for coronary artery bypass graft surgery with cardiopulmonary bypass. Eculizumab is a long-acting anti-C5 antibody used for paroxysmal nocturnal hemoglobinuria, rheumatoid arthritis, membranous glomerulonephritis with promising results.     

Clinical aspects of pneumonia

Pneumonia is a serious medical condition and a major cause of morbidity and mortality worldwide. It has many infectious aetiologies, although bacterial and viral forms are most common. Our understanding of pneumonia has improved significantly during the course of the 20th century but the overall disease burden has changed little. Although antibiotics have helped to reduce the mortality associated with some types of pneumonia, the level of morbidity remains constant. Furthermore, the existence of antibiotic-resistant bacteria worldwide is becoming an increasing problem in treatment. This essay describes the different types of pneumonia from a clinical perspective and highlights the problems associated with the condition.     

Clinical and epidemiological aspects in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is defined by the occurrence of venous and arterial thromboses, often multiple, and pregnancy morbidity (mainly, recurrent fetal losses and premature births), frequently accompanied by a moderate thrombocytopenia, in the presence of antiphospholipid antibodies (aPL), namely lupus anticoagulant (LA), anticardiolipin antibodies (aCL), or both. Other autoantibodies have also been detected in many patients with an APS, such as anti-beta2 glycoprotein I (GPI), antimitochondrial (M5 type), antiendothelial cell, antiplatelet, antierythrocyte, and antinuclear antibodies. The APS can be found in patients having neither clinical nor laboratory evidence of another definable condition (primary APS) or it may be associated with other diseases. Systemic lupus erythematosus (SLE) is the disorder in which an APS is most commonly associated. Less frequently, aPL and, rarely, an APS may also be encountered in other groups of patients (Table 1) (1).