A lethal autosomal recessive syndrome of multiple congenital contractures

The Finnish genetic heritage in 2022 – from diagnosis to translational research

Isolated populations have been valuable for the discovery of rare monogenic diseases and their causative genetic variants. Finnish disease heritage (FDH) is an example of a group of hereditary monogenic disorders caused by single major, usually autosomal-recessive, variants enriched in the population due to several past genetic drift events. Interestingly, distinct subpopulations have remained in Finland and have maintained their unique genetic repertoire. Thus, FDH diseases have persisted, facilitating vigorous research on the underlying molecular mechanisms and development of treatment options. This Review summarizes the current status of FDH, including the most recently discovered FDH disorders, and introduces a set of other recently identified diseases that share common features with the traditional FDH diseases. The Review also discusses a new era for population-based studies, which combine various forms of big data to identify novel genotype–phenotype associations behind more complex conditions, as exemplified here by the FinnGen project. In addition to the pathogenic variants with an unequivocal causative role in the disease phenotype, several risk alleles that correlate with certain phenotypic features have been identified among the Finns, further emphasizing the broad value of studying genetically isolated populations.

Post-transcriptional regulation of gene expression and human disease

A large number of mutations in genes that encode RNA binding proteins cause human disease. Many of these RNA binding proteins mediate key steps in post-transcriptional regulation of gene expression from mRNA processing to eventual decay in the cytoplasm. Surprisingly, these RNA binding proteins, which are ubiquitously expressed and play fundamental roles in gene expression, are often altered in tissue-specific disease. Mutations linked to disease impact nearly every post-transcriptional processing step and cause diverse disease phenotypes in a variety of specific tissues. This review summarizes steps in post-transcriptional regulation of gene expression that have been linked to disease providing specific examples of some of the many genes affected. Finally, recent advances that hold promise for treatment of some of these diseases are presented.

The roles of intrinsic disorder-based liquid-liquid phase transitions in the "Dr. Jekyll-Mr. Hyde" behavior of proteins involved in amyotrophic lateral sclerosis and frontotemporal lobar degeneration

Pathological developments leading to amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are associated with misbehavior of several key proteins, such as SOD1 (superoxide dismutase 1), TARDBP/TDP-43, FUS, C9orf72, and dipeptide repeat proteins generated as a result of the translation of the intronic hexanucleotide expansions in the C9orf72 gene, PFN1 (profilin 1), GLE1 (GLE1, RNA export mediator), PURA (purine rich element binding protein A), FLCN (folliculin), RBM45 (RNA binding motif protein 45), SS18L1/CREST, HNRNPA1 (heterogeneous nuclear ribonucleoprotein A1), HNRNPA2B1 (heterogeneous nuclear ribonucleoprotein A2/B1), ATXN2 (ataxin 2), MAPT (microtubule associated protein tau), and TIA1 (TIA1 cytotoxic granule associated RNA binding protein). Although these proteins are structurally and functionally different and have rather different pathological functions, they all possess some levels of intrinsic disorder and are either directly engaged in or are at least related to the physiological liquid-liquid phase transitions (LLPTs) leading to the formation of various proteinaceous membrane-less organelles (PMLOs), both normal and pathological. This review describes the normal and pathological functions of these ALS- and FTLD-related proteins, describes their major structural properties, glances at their intrinsic disorder status, and analyzes the involvement of these proteins in the formation of normal and pathological PMLOs, with the ultimate goal of better understanding the roles of LLPTs and intrinsic disorder in the "Dr. Jekyll-Mr. Hyde" behavior of those proteins.

The importance of managing the patient and not the gene: expanded phenotype of GLE1-associated arthrogryposis

GLE1 encodes a protein important for mRNA export and appears to play roles in translation initiation and termination as well. Pathogenic variants in GLE1 mutations have been associated with lethal contracture syndrome and lethal arthrogryposis with anterior horn cell disease; phenotypes reported in individuals include fetal akinesia and a severe form of motor neuron disease, typically presenting with prenatal symptoms and perinatal lethality. In this article, we identified biallelic missense mutations in GLE1 by trio whole-exome sequencing in an individual affected with congenital motor weakness and contractures as well as feeding and respiratory difficulties. Muscle biopsy was consistent with anterior horn cell disease and supported the pathogenicity of the sequence variants. Importantly, this individual survived past the perinatal period with respiratory support and currently demonstrates age-appropriate cognition and slow but steady motor developmental progress. We propose that pathogenic variants in GLE1 can be associated with a nonperinatal lethal motor phenotype, and affected individuals can demonstrate motor skill progression, unlike prototypical anterior horn cell diseases such as spinal muscular atrophy.

Survival beyond the perinatal period expands the phenotypes caused by mutations in GLE1

Mutations in GLE1 underlie Lethal Congenital Contracture syndrome (LCCS) and Lethal Arthrogryposis with Anterior Horn Cell Disease (LAAHD). Both LCCS and LAAHD are characterized by reduced fetal movements, congenital contractures, and a severe form of motor neuron disease that results in fetal death or death in the perinatal period, respectively. We identified bi-allelic mutations in GLE1 in two unrelated individuals with motor delays, feeding difficulties, and respiratory insufficiency who survived beyond the perinatal period. Each affected child had missense variants predicted to result in amino acid substitutions near the C-terminus of GLE1 that are predicted to disrupt protein-protein interaction or GLE1 protein targeting. We hypothesize that mutations that preserve function of the coiled-coil domain of GLE1 cause LAAHD whereas mutations that abolish the function of the coiled-coil domain cause LCCS. The phenotype of LAAHD is now expanded to include multiple individuals surviving into childhood suggesting that LAAHD is a misnomer and should be re-named Arthrogryposis with Anterior Horn Cell Disease (AAHD).

A role for Gle1, a regulator of DEAD-box RNA helicases, at centrosomes and basal bodies

Control of organellar assembly and function is critical to eukaryotic homeostasis and survival. Gle1 is a highly conserved regulator of RNA-dependent DEAD-box ATPase proteins, with critical roles in both mRNA export and translation. In addition to its well-defined interaction with nuclear pore complexes, here we find that Gle1 is enriched at the centrosome and basal body. Gle1 assembles into the toroid-shaped pericentriolar material around the mother centriole. Reduced Gle1 levels are correlated with decreased pericentrin localization at the centrosome and microtubule organization defects. Of importance, these alterations in centrosome integrity do not result from loss of mRNA export. Examination of the Kupffer's vesicle in Gle1-depleted zebrafish revealed compromised ciliary beating and developmental defects. We propose that Gle1 assembly into the pericentriolar material positions the DEAD-box protein regulator to function in localized mRNA metabolism required for proper centrosome function.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

Protein kinases are one of the largest families of evolutionarily related proteins and the third most common protein class of human genome. All the protein kinases share the same structural organization. They are made up of an extracellular domain, transmembrane domain and an intra cellular kinase domain. Missense mutations in these kinases have been studied extensively and correlated with various neurological disorders. Individual mutations in the kinase domain affect the functions of protein. The enhanced or reduced expression of protein leads to hyperactivation or inactivation of the signalling pathways, resulting in neurodegeneration. Here, we present extensive analyses of missense mutations in the tyrosine kinase focussing on the neurodegenerative diseases encompassing structure function relationship. This is envisaged to enhance our understanding about the neurodegeneration and possible therapeutic measures.

Control of mammalian gene expression by selective mRNA export

Nuclear export of mRNAs is a crucial step in the regulation of gene expression, linking transcription in the nucleus to translation in the cytoplasm. Although important components of the mRNA export machinery are well characterized, such as transcription-export complexes TREX and TREX-2, recent work has shown that, in some instances, mammalian mRNA export can be selective and can regulate crucial biological processes such as DNA repair, gene expression, maintenance of pluripotency, haematopoiesis, proliferation and cell survival. Such findings show that mRNA export is an unexpected, yet potentially important, mechanism for the control of gene expression and of the mammalian transcriptome.

Deleterious mutations in the essential mRNA metabolism factor, hGle1, in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective death of motor neurons. Causative mutations in the global RNA-processing proteins TDP-43 and FUS among others, as well as their aggregation in ALS patients, have identified defects in RNA metabolism as an important feature in this disease. Lethal congenital contracture syndrome 1 and lethal arthrogryposis with anterior horn cell disease are autosomal recessive fetal motor neuron diseases that are caused by mutations in another global RNA-processing protein, hGle1. In this study, we carried out the first screening of GLE1 in ALS patients (173 familial and 760 sporadic) and identified 2 deleterious mutations (1 splice site and 1 nonsense mutation) and 1 missense mutation. Functional analysis of the deleterious mutants revealed them to be unable to rescue motor neuron pathology in zebrafish morphants lacking Gle1. Furthermore, in HeLa cells, both mutations caused a depletion of hGle1 at the nuclear pore where it carries out an essential role in nuclear export of mRNA. These results suggest a haploinsufficiency mechanism and point to a causative role for GLE1 mutations in ALS patients. This further supports the involvement of global defects in RNA metabolism in ALS.

Insights into mRNA export-linked molecular mechanisms of human disease through a Gle1 structure-function analysis

A critical step during gene expression is the directional export of nuclear messenger (m)RNA through nuclear pore complexes (NPCs) to the cytoplasm. During export, Gle1 in conjunction with inositol hexakisphosphate (IP6) spatially regulates the activity of the DEAD-box protein Dbp5 at the NPC cytoplasmic face. GLE1 mutations are causally linked to the human diseases lethal congenital contracture syndrome 1 (LCCS-1) and lethal arthrogryposis with anterior horn cell disease (LAAHD). Here, structure prediction and functional analysis provide strong evidence to suggest that the LCCS-1 and LAAHD disease mutations disrupt the function of Gle1 in mRNA export. Strikingly, direct fluorescence microscopy in living cells reveals a dramatic loss of steady-state NPC localization for GFP-gle1 proteins expressed from human gle1 genes harboring LAAHD and LCCS-1 mutations. The potential significance of these residues is further clarified by analyses of sequence and predicted structural conservation. This work offers insights into the perturbed mechanisms underlying human LCCS-1 and LAAHD disease states and emphasizes the potential impact of altered mRNA transport and gene expression in human disease.

Gle1 functions during mRNA export in an oligomeric complex that is altered in human disease

The conserved multifunctional protein Gle1 regulates gene expression at multiple steps: nuclear mRNA export, translation initiation, and translation termination. A GLE1 mutation (FinMajor) is causally linked to human lethal congenital contracture syndrome-1 (LCCS1); however, the resulting perturbations on Gle1 molecular function were unknown. FinMajor results in a proline-phenylalanine-glutamine peptide insertion within the uncharacterized Gle1 coiled-coil domain. Here, we find that Gle1 self-associates both in vitro and in living cells via the coiled-coil domain. Electron microscopy reveals that high-molecular-mass Gle1 oligomers form ?26 nm diameter disk-shaped particles. With the Gle1-FinMajor protein, these particles are malformed. Moreover, functional assays document a specific requirement for proper Gle1 oligomerization during mRNA export, but not for Gle1's roles in translation. These results identify a mechanistic step in Gle1's mRNA export function at nuclear pore complexes and directly implicate altered export in LCCS1 disease pathology.

Arthrogryposis and fetal hypomobility syndrome

Arthrogryposis is a heterogeneous condition, evident from birth, which can be defined as multiple contractures of the joints. The etiology is multifold: genetic disorders of the central or peripheral nervous system, or of the connective tissue leading to decreased fetal movements, and vascular and environmental causes. The problem begins in utero. There may be overlapping conditions between sporadic, syndromic, neurogenic, myopathic and metabolic types. The workup should include a family tree. Systemic involvement, for example of the renal and pulmonary systems, may be encountered in associated syndromes. Motor neuron disorders leading to the condition are the most commonly seen type. Fetal or neonatal akinesia/hypokinesia is at the severe end of the spectrum, in which there is literally intrauterine limitation of movement. Children with amyplasia are born with little or diminished muscle bulk of the extremities. Distal arthrogryposis is almost always a dominantly inherited condition. A multidisciplinary care approach is required in order to provide optimum healthcare. The management team should include a nutritionist and a physiotherapist. Genetic counseling is possible in most instances. A truly genetic cause can be identified in more than 50% of cases. Survivors, though handicapped, can lead near normal lives.

Diagnosing arthrogryposis multiplex congenita: a review

Arthrogryposis multiplex congenita (AMC) refers either to a syndromic or to a nonsyndromic group of conditions with varied etiology and complex clinical features, including multiple congenital contractures in different body areas. Its etiology still remains unclear but generally any cause that leads to reduced fetal movement may lead to congenital contractures and in severe cases to fetal akinesia deformation sequence (FADS). It affects approximately 1 in 2-3000 live births with an approximately equal gender ratio. There are many known subgroups of AMC differing in signs, symptoms, and causes. The primary diagnosis is made when a lack of mobility and an abnormal position is noted in routine ultrasound scanning. Early diagnosis, prenatal evaluation, and further surveillance via image scanning (ultrasound and MRI) give the opportunity for family counseling concerning neonatal morbidity and mortality and labor or delivery planning. Better understanding of the ultrasound findings and the etiology of this clinical situation offers the opportunity for careful prenatal assessment.

A zebrafish model of lethal congenital contracture syndrome 1 reveals Gle1 function in spinal neural precursor survival and motor axon arborization

In humans, GLE1 is mutated in lethal congenital contracture syndrome 1 (LCCS1) leading to prenatal death of all affected fetuses. Although the molecular roles of Gle1 in nuclear mRNA export and translation have been documented, no animal models for this disease have been reported. To elucidate the function of Gle1 in vertebrate development, we used the zebrafish (Danio rerio) model system. gle1 mRNA is maternally deposited and widely expressed. Altering Gle1 using an insertional mutant or antisense morpholinos results in multiple defects, including immobility, small eyes, diminished pharyngeal arches, curved body axis, edema, underdeveloped intestine and cell death in the central nervous system. These phenotypes parallel those observed in LCCS1 human fetuses. Gle1 depletion also results in reduction of motoneurons and aberrant arborization of motor axons. Unexpectedly, the motoneuron deficiency results from apoptosis of neural precursors, not of differentiated motoneurons. Mosaic analyses further indicate that Gle1 activity is required extrinsically in the environment for normal motor axon arborization. Importantly, the zebrafish phenotypes caused by Gle1 deficiency are only rescued by expressing wild-type human GLE1 and not by the disease-linked Fin(Major) mutant form of GLE1. Together, our studies provide the first functional characterization of Gle1 in vertebrate development and reveal its essential role in actively dividing cells. We propose that defective GLE1 function in human LCCS1 results in both neurogenic and non-neurogenic defects linked to the apoptosis of proliferative organ precursors.

RNA processing defects associated with diseases of the motor neuron

Rapid progress in the discovery of motor neuron disease genes in amyotrophic lateral sclerosis, the spinal muscular atrophies, hereditary motor neuropathies, and lethal congenital contracture syndromes is providing new perspectives and insights into the molecular pathogenesis of the motor neuron. Motor neuron disease genes are often expressed throughout the body with essential functions in all cells. A survey of these functions indicates that motor neurons are uniquely sensitive to perturbations in RNA processing pathways dependent on the interaction of specific RNAs with specific RNA-binding proteins, which presumably result in aberrant formation and function of ribonucleoprotein complexes. This review provides a summary of currently recognized RNA processing defects linked to human motor neuron diseases.

Pena-Shokeir phenotype (fetal akinesia deformation sequence) revisited

BACKGROUND

Pena and Shokeir described the phenotype of two sisters in 1974, and subsequently their features have become recognized as a sequence of deformational changes related to decreased or absent fetal movement (fetal akinesia deformation sequence [FADS]), because of the work of Moessinger (1983).

METHODS

Identification of reported cases by searching Online Mendelian Inheritance in Man, Medlines, the London Dysmorphology Database, and the references found in these articles. These case reports were reviewed, tabulated, and summarized.

RESULTS

It is now possible to recognize at least 20 familial types of Pena-Shokeir phenotype (PSP), based on the differences found in the reports of the natural history and pathology found at fetal and newborn autopsy. In addition, characteristic changes in the central nervous system seen with embryonic/fetal vascular compromise have been recognized in many reported cases. Most of the reported cases of PSP/FADS related to vascular compromise are sporadic, but familial cases have also been reported.

CONCLUSION

Lack of fetal movement (fetal akinesia) in humans produces a recognizable sequence of deformations. Many developmental processes must be accomplished for fetal movement to be normal, and for extra-uterine life to be sustainable. Prenatal diagnosis is possible through real-time ultrasound studies as early as 12 weeks. Most reported cases die in utero, at birth, or in the newborn period. Advances in embryo/fetus pathology have led to the recognition of the many familial subtypes, allowing improved genetic counseling and early recognition in subsequent pregnancies.

Lethal contractural syndrome type 3 (LCCS3) is caused by a mutation in PIP5K1C, which encodes PIPKI gamma of the phophatidylinsitol pathway

Lethal congenital contractural syndrome (LCCS) is a severe form of arthrogryposis. To date, two autosomal recessive forms of the disease (LCCS and LCCS2) have been described and mapped to chromosomes 9q34 and 12q13, respectively. We now describe a third LCCS phenotype (LCCS3)--similar to LCCS2 yet without neurogenic bladder. Using 10K single-nucleotide-polymorphism arrays, we mapped the disease-associated gene to 8.8 Mb on chromosome 19p13. Further analysis using microsatallite markers narrowed the locus to a 3.4-Mb region harboring 120 genes. Of these genes, 30 candidates were sequenced, which identified a single homozygous mutation in PIP5K1C. PIP5K1C encodes phosphatidylinositol-4-phosphate 5-kinase, type I, gamma (PIPKI gamma ), an enzyme that phophorylates phosphatidylinositol 4-phosphate to generate phosphatidylinositol-4,5-bisphosphate (PIP(2)). We demonstrate that the mutation causes substitution of aspartic acid with asparagine at amino acid 253 (D253N), abrogating the kinase activity of PIPKI gamma . Thus, a defect in the phosphatidylinositol pathway leading to a decrease in synthesis of PIP(2), a molecule active in endocytosis of synaptic vesicle proteins, culminates in lethal congenital arthrogryposis.

Neural precursor cells from a fatal human motoneuron disease differentiate despite aberrant gene expression

Precursor cells of the human central nervous system can be cultured in vitro to reveal pathogenesis of diseases or developmental disorders. Here, we have studied the biology of neural precursor cells (NPCs) from patients of lethal congenital contracture syndrome (LCCS), a severe motoneuron disease leading to prenatal death before the 32nd gestational week. LCCS fetuses are immobile because of a motoneuron defect, seen as degeneration of the anterior horn and descending tracts of the developing spinal cord. The genetic defect for the syndrome is unknown. We show that NPCs isolated postmortem from LCCS fetuses grow and are maintained in culture, but display increased cell cycle activity. Global transcript analysis of undifferentiated LCCS precursor cells present with changes in EGF-related signaling when compared with healthy age-matched human controls. Further, we show that LCCS-derived NPCs differentiate into cells of neuronal and glial lineage and that the initial differentiation is not accompanied by overt apoptosis. Cells expressing markers Islet-1 and Hb9 are also generated from the LCCS NPCs, suggesting that the pathogenic mechanism of LCCS does not directly affect the differentiation capacity or survival of the cells, but the absence of motoneurons in LCCS may be caused by a noncell autonomous mechanism.

Genetics of arthrogryposis: linkage analysis approach

Arthrogryposis multiplex congenita (AMC) is a heterogeneous group of congenital contracture syndromes, some of which are hereditary. To date, four genetic loci associated with autosomal recessive arthrogryposis syndromes have been identified using the powerful tools of genome-wide linkage analysis and homozygosity mapping. In the consanguineous inbred Bedouin population in southern Israel there is an unusually high incidence of hereditary arthrogryposis. We hypothesized the high incidence of this phenotype in this specific cohort might be due to a founder effect: a mutation that occurred several generations ago, spread throughout various tribes in that population in recent generations and causes the phenotype in its homozygous form. Using linkage analysis studies, we showed the hereditary arthrogryposis in those tribes does not stem from a single genetic defect. Thus, there is genetic heterogeneity of congenital arthrogryposis in this population: the same phenotype is caused by mutations in different genes, yet to be unraveled.

Lethal congenital contracture syndrome (LCCS) and other lethal arthrogryposes in Finland—An epidemiological study

Arthrogryposis multiplex congenita is a heterogeneous group of disorders characterized by multiple contractures with an estimated frequency of 1 in 3,000 births. With improving diagnostic methods, increasing numbers of fetuses with arthrogryposis are found. The pathogenetic mechanisms are relatively well known but the epidemiology and genetics of the prenatally lethal forms of arthrogryposis are less well known. In this study we collected all cases of a multiple contractures diagnosed in Finland during 1987-2002 including live born infants, stillbirths, and terminated pregnancies. Ninety-two cases of 214 suffered intrauterine demise (68 selective pregnancy terminations and 24 stillbirths) and 58 died in infancy. In 141 out of these cases the diagnosis could be included within lethal arthrogryposes, with a prevalence of 1 in 6,985 (1.43/10,000) births. Of these, 59 had spinal cord pathology at autopsy and thus were of neurogenic origin. Thirty-nine cases had lethal congenital contracture syndrome (LCCS) clinically characterized by total immobility of the fetus at all ultrasound examinations (12 weeks or later), multiple joint contractures in both upper and lower limbs, hydrops, and fetal death before the 32nd week of pregnancy. LCCS is noted as a unique Finnish disorder with a prevalence of 1 in 25,250 (0.40/10,000) births and is a major cause of lethal arthrogryposis in Finland.

Indicative oligodendrocyte dysfunction in spinal cords of human fetuses suffering from a lethal motoneuron disease

Human spinal cord development is still poorly understood and detailed molecular analyses of human motoneuron diseases could improve our understanding of the normal developmental processes of the spinal cord. Lethal Congenital Contracture Syndrome (LCCS, MIM 253310) provides a human model to study the early motoneuronal development. A typical phenotype of LCCS fetuses consists of multiple joint contractures, distinct facial features, and hydrops. Tissue pathology is characterized by severe muscle atrophy, lung hypoplasia, and degeneration of the anterior horn of the spinal cord as the hallmark of the syndrome. In this study we performed a global transcript analysis of LCCS spinal cords. The RNA expression profiles of these spinal cords were compared to age-matched healthy control fetuses, aborted for nonrelated causes. In addition, we applied phylogenetic footprinting methods to decipher the mechanisms of transcriptional regulation in the affected transcripts. Changes in transcripts involved with the development of the CNS and oligodendrocytes were obvious and the transcription factor PAX6 was identified as a key regulator during spinal cord development. In addition, transcript pathway analysis clearly indicated genes belonging to groups with neuronal functions to be affected. Our findings support the hypothesis that human motoneurons and oligodendrocytes are dependent on each other during their development and are influenced by distinct transcription factors previously known to act during murine and chick motoneuron development. These data provide valuable information about the molecular pathways putatively active in motoneuron diseases.

Evaluation of a protocol for postmortem examination of stillbirths and neonatal deaths with congenital anomalies

A study was conducted on 75 perinatal deaths with congenital anomalies through clinical, radiographic, cytogenetic, and autopsy evaluation, and the diagnoses of 72 patients (96%) were determined. In 11 patients with chromosomal anomalies, the cytogenetic study was sufficient to determine the diagnosis and the reproductive risk. In these cases, the value of the autopsy results resided above all in the description of the clinical variability. Radiographic evaluation was the best method to establish a diagnosis of skeletal dysplasias (14.7%). Furthermore, the X-rays showed small skeletal defects which are difficult to see on dissection. The clinical genetic evaluation with a detailed description of the phenotype and anthropometric exam, performed by a clinical geneticist, and the autopsy with gross and microscopic evaluation, facilitated the diagnoses of 50 cases (66.7%). We concluded that, in perinatal death with congenital anomalies, the teamwork of clinical geneticists and fetal pathologists increases the probability of determining the etiological diagnosis. This is essential to define the parents' reproductive risk, thus contributing to primary prevention of congenital anomalies.

The Finnish Disease Heritage III: the individual diseases

This article is the third and last in a series entitled The Finnish Disease Heritage I-III. All the 36 rare hereditary diseases belonging to this entity are described for clinical and molecular genetic purposes, based on the Finnish experience gathered over a period of half a century. In addition, five other diseases are mentioned. They may be included in the list of the "Finnish diseases" after adequate complementary studies.

A new autosomal recessive congenital contractural syndrome in an Israeli Bedouin kindred

We describe 23 cases with a syndrome of congenital contractures belonging to a large, inbred Israeli-Bedouin kindred. The phenotype described is similar to the Finnish type lethal congenital contracture syndrome yet differs in the following ways: by some additional craniofacial/ocular findings, by the lack of hydrops, multiple pterygia, and fractures, and by the normal duration of pregnancy. The major unique and previously undescribed clinical feature in our patients is a markedly distended urinary bladder as well as other urinary abnormalities. The vast majority of the cases died shortly after birth. Sonographic prenatal diagnosis was possible as early as 15 weeks gestation by demonstrating fetal akinesia, limb contractures, hydramnios, and distended urinary bladder. Linkage to 5q and 9q34 loci has been excluded.

Diversity of neuromuscular pathology in lethal multiple pterygium syndrome

Lethal multiple pterygium syndrome (LMPS) is an uncommon fetal-onset disorder of unknown etiology. The pathogenesis of LMPS has been suggested to be early-onset fetal akinesia, fragile collagen, or generalized edema. Information on the neuromuscular pathology of LMPS in the literature is generally scanty. We present the findings from a review of 14 fetuses with features of LMPS from the archives of the Hammersmith Hospital Perinatal Pathology Department. Autopsy reports, photographs, fetograms, and histological sections were examined, and additional special stains and immunostaining were performed on muscle sections. In five cases, there was evidence of autosomal recessive inheritance. One case was later shown to be due to glycogen storage disease type IV. The skeletal muscle bulk was reduced in all fetuses and the remaining muscle showed a range of histological appearances including vacuolar degeneration, dystrophy, a generalized or patchy myotubular appearance, and generalized hypotrophy. In one, the histological appearance was essentially normal. Two cases had abnormalities in the brain. Large motor neurons were present in the anterior spinal horns of all fetuses in whom the spinal cord could be examined. There was no evidence of cartilaginous joint fusion. We conclude that LMPS is the phenotype resulting from fetal akinesia commencing in the first or early second trimester. In the majority of cases, the precise underlying cause will not be identified, however, occasionally a metabolic or neurodevelopmental disorder or a specific primary myopathy may be demonstrated, providing adequate autopsy investigations are undertaken.

Heterogeneity in fetal akinesia deformation sequence (FADS): autopsy confirmation in three 20-21-week fetuses

Fetal akinesia deformation sequence (FADS) is a rare condition characterized by intrauterine growth retardation (IUGR), congenital limb contractures, pulmonary hypoplasia, hydramnios and craniofacial abnormalities. The present report comprises an autopsy study of three fetuses to illustrate the variable clinical manifestations and neuropathological findings. Fetus 1 had arthrogryposis and no movement on fetal ultrasound examination. Aborted at 21 weeks, the fetus showed micrognathia, bilateral joint contracture with pterygia at the elbow and axilla. Growth retardation and pulmonary hypoplasia were not major features. Neuropathologic examination revealed anterior horn cell loss and lateral corticospinal tract degeneration in spinal cord, with marked muscular atrophy. Fetus 2, 20 weeks' gestation, had fetal akinesia, nuchal thickening, left pleural effusion, and Dandy-Walker malformation on ultrasound examination. Autopsy showed low-set ears, ocular hypertelorism, cleft palate, flexion contractures with pterygia over axilla, elbow and groin, pulmonary hypoplasia, Dandy-Walker malformation, unremarkable spinal cord and skeletal muscle. Fetus 3, 21 weeks' gestation, was aborted for fetal akinesia, neck and limb webbing and severe arthrogryposis. At autopsy, similar facial abnormalities, contracture and pterygia in neck and multiple major joints were found. Borderline pulmonary hypoplasia and severe lumbar scoliosis were also present. The brain, spinal cord and muscle were unremarkable. In these three fetuses, the prenatal ultrasound and autopsy findings were characteristic of FADS. Neurogenic spinal muscular atrophy was the basis of fetal akinesia in Case 1. Dandy-Walker malformation was present in Case 2, but the pathogenetic mechanism of fetal akinesia was not clear as spinal cord and muscle histology appeared normal. The etiology of akinesia was undetermined in Case 3; no extrinsic or intrinsic cause was identified.

Non-lethal arthrogryposis multiplex congenita presenting with cystic hygroma at 13 weeks gestational age

Arthrogryposis is defined as multiple joint contractures, the aetiology of which is variable. Prenatal diagnosis has focused on diminshed fetal movement and detection of joint contractures on ultrasound. These findings usually do not become evident until 16 to 18 weeks of gestation. Although others (Baty, 1989; Hyett et al., 1997) have reported the diagnosis of arthrogryposis in the first and early second trimester by the presence of nuchal oedema, these reports have all focused on lethal conditions. We report on two female siblings with non-lethal arthrogryposis multiplex congenita. The diagnosis was suspected in the second pregnancy at 13.5 weeks when a large cystic hygroma was detected on ultrasound. Multiple joint contractures became evident at 18 weeks. We hypothesize that the aetiology may be secondary to delay in lymphatic maturation with development of a large cystic hygroma resulting in restriction of fetal movement during early joint formation. Further, the fact that the two female siblings had a similar pattern of facial and joint development, and that their parents are second cousins, suggests an autosomal recessive basis for this form of AMC.

Linkage disequilibrium mapping in isolated populations: the example of Finland revisited

Linkage disequilibrium analysis can provide high resolution in the mapping of disease genes because it incorporates information on recombinations that have occurred during the entire period from the mutational event to the present. A circumstance particularly favorable for high-resolution mapping is when a single founding mutation segregates in an isolated population. We review here the population structure of Finland in which a small founder population some 100 generations ago has expanded into 5.1 million people today. Among the 30-odd autosomal recessive disorders that are more prevalent in Finland than elsewhere, several appear to have segregated for this entire period in the "panmictic" southern Finnish population. Linkage disequilibrium analysis has allowed precise mapping and determination of genetic distances at the 0.1-cM level in several of these disorders. Estimates of genetic distance have proven accurate, but previous calculations of the confidence intervals were too small because sampling variation was ignored. In the north and east of Finland the population can be viewed as having been "founded" only after 1500. Disease mutations that have undergone such a founding bottleneck only 20 or so generations ago exhibit linkage disequilibrium and haplotype sharing over long genetic distances (5-15 cM). These features have been successfully exploited in the mapping and cloning of many genes. We review the statistical issues of fine mapping by linkage disequilibrium and suggest that improved methodologies may be necessary to map diseases of complex etiology that may have arisen from multiple founding mutations.

Assignment of the disease locus for lethal congenital contracture syndrome to a restricted region of chromosome 9q34, by genome scan using five affected individuals

Lethal congenital contracture syndrome (LCCS) is an autosomal recessive disease leading to death before the 32d gestational week. It is characterized by the fetal akinesia phenotype, with highly focused degeneration of motoneurons in the spinal cord as the main neuropathological finding. We report here the assignment of the LCCS locus to a defined region of chromosome 9q34, between markers D9S1825 and D9S1830. The initial genome scan was performed with the DNA samples of only five affected individuals from two unrelated LCCS families. The conventional linkage analysis performed with 20 affected individuals and their families was focused on those chromosomal regions in which the affected siblings were identical by descent in the initial scan. One core haplotype of 3 cM was observed in LCCS alleles, supporting the assumption of one major mutation underlying LCCS, and linkage disequilibrium analysis restricted the critical chromosomal region to <100 kb in the vicinity of marker D9S61. Two genes, NGAL (neutrophil gelatinase-associated lipocalin and NOTCH 1, were excluded as causative genes for LCCS

Lethal multiple pterygium syndrome: suggestion for a consistent pathological workup and review of reported cases

We report on 2 brothers with lethal multiple pterygium syndrome (LMPS) born to non-consanguineous parents as late spontaneous abortions. Both fetuses presented with massive nuchal edema, and facial anomalies including cleft palate and broad ribs. Apparently, several subgroups of LMPS exist. Differentiation is difficult, as there is no consistent agreement on a workup protocol for autopsies. We compared the findings in the literature on cases with LMPS, and we suggest a standardized workup as an initial step for more efficient differentiation between various subgroups.

Two sisters with Escobar syndrome

We report on 2 sisters with an autosomal-recessive multiple pterygium syndrome, type Escobar, consisting of multiple pterygia with severe contractures, short stature, and minor facial and external genital anomalies. The striking finding was severe muscular atrophy. We speculate that a neuromuscular disorder is the underlying pathogenesis of Escobar syndrome.

Lethal arthrogryposis multiplex congenital (fetal akinesia deformation sequence, FADS)

Arthrogryposis multiplex congenital (AMC) is the presence at birth of multiple congenital contractures in an intact skeleton. The severity of the condition is highly variable and the possible underlying causes are numerous. Fetal immobility and lesions of the brain, spinal cord, peripheral nerves and muscle, along with mechanical restriction of the fetus in utero are the pathogenic mechanisms that need to be considered. Etiological factors that have been implicated in the development of AMC include genetic conditions, infections, drugs, toxins, maternal hyperthermia, and maternal illness. This review will concentrate on the severe end of the spectrum of AMC that results in disease that is lethal pre- or postnatally, and will discuss the pathology, pathogenesis, etiology, and practical approach to this diversely expressed condition.

Fetal akinesia

Normal fetal growth and development during pregnancy is highly dependent upon adequate fetal movement. Limitation of movement, regardless of the underlying cause, can result in a particular pattern of abnormal fetal morphogenesis. This phenotype is termed the fetal akinesia deformation sequence (FADS). The etiology of fetal akinesia may be generally classified into one of five categories: neuropathy, myopathy, restrictive dermopathy, teratogen exposure, or restricted movement due to intrauterine constraint. In this article, the differential diagnosis of fetal akinesia is systematically reviewed and information regarding prenatal diagnosis, prognosis, perinatal management, and recurrence risks are discussed.

Fetal akinesia and multiple perinatal fractures

Two newborn infants with fetal akinesia sequence were noted to have multiple perinatal fractures of the long bones. The radiographic manifestations are characterized by gracile ribs, thin long bones, and multiple diaphyseal fractures. Consistent histopathologic changes of bone are irregular with focal areas of extreme diaphyseal thinning, thin and long marrow spicules, and with or without callous formation at fracture sites. Pathogenic mechanisms of bone fractures in fetal akinesia sequence and the differential diagnoses of congenital/perinatal bone fractures are discussed.

Lethal congenital contracture syndrome (LCCS), a fetal anterior horn cell disease, is not linked to the SMA 5q locus

The lethal congenital contracture syndrome (LCCS) is an autosomal recessive syndrome (McKusick 253310) leading to perinatal death owing to early onset degeneration of the anterior horn motor neurones of the spinal cord. The neuropathological findings in the LCCS closely resemble those of spinal muscular atrophy (SMA). Since all the three types of SMA have been localised to the same gene locus on the long arm of chromosome 5, we analysed samples from seven families with 10 LCCS fetuses with the microsatellite markers assigned to the SMA 5q region. Linkage analyses between the SMA linked DNA markers and the disease allele in the LCCS families excluded the critical chromosomal region around the SMA locus as the critical chromosomal region for the LCCS locus.

Lethal arthrogryposis with anterior horn cell disease

Fifteen infants (11 families) with lethal arthrogryposis and anterior horn motor neuron loss are described. The clinical presentation was the fetal akinesia deformation sequence (FADS) with multiple contractures and facial anomalies. At autopsy neurogenic muscular atrophy was present in all infants. The spinal cord showed a paucity of anterior horn motor neurons in the 12 infants studied. Both male and female infants were affected. Nine cases were sporadic, whereas in two families there were three affected cases. Consanguinity between the parents was reported in one family with one affected child. This and the recurrence of the condition speak for autosomal recessive inheritance. Detailed neuropathological examination and documentation of the clinical features are needed for a better delineation of and genetic counseling for perinatally lethal arthrogryposis.

Osteocraniostenosis

We report a multiple congenital anomalies (MCA) syndrome in three unrelated fetuses consisting of extremely thin, dense, fishbone-like diaphyses, flared metaphyses, mild micromelic dwarfism, brachydactyly, facial dysmorphism, ocular malformations (microphthalmia, aniridia), cloverleaf skull deformity, and splenic hypoplasia. Histopathological investigations showed abnormalities of the metaphyseal cartilage and adjacent diaphyseal ossification, excessive modelling of the metaphyses, and, in one case, dysplasia of the epiphyseal cartilage. We review three previously reported cases. We suggest the name osteocraniostenosis to describe this radiological and clinical disorder, pinpointing its major clinical and radiological features.

Lethal congenital contracture syndrome: further delineation and genetic aspects

In a national morphology based study of lethal arthrogryposis between 1979 and 1992, 40 fetuses and infants with lethal congenital contracture syndrome (LCCS, McKusick 253310) were found in Finland. The incidence of LCCS in Finland was 1:19,000 births. There were 20 affected males and 20 affected females in 26 families. In 16 cases the pregnancy was terminated after the prenatal diagnosis of total akinesia and fetal hydrops on ultrasound. There were 19 stillborn infants and five were born showing signs of life, but died within one hour. The segregation analyses yielded 0.45 affected by the "singles" method and 0.34 by the "sib" method. The birthplaces of the grandparents were located in the sparsely populated north east of Finland. This finding supports the existence of an autosomal recessive LCCS gene in Finland, particularly in the north eastern part.

Sonographic Evaluation of Arthrogrypotic Conditions

The term arthrogryposis is applied to a large group of conditions that result in joint contractures, abnormal positioning of hands or feet, and other neuromuscular defects. Abnormalities of the brain, spinal cord, peripheral nerves, muscles, or connective tissue lead to similar joint stiffness and contractures. Careful sonographic examination of an affected fetus can provide valuable information that will help in the assessment of diagnosis, prognosis, and risk of recurrence.

Lethal multiple pterygium syndrome: report of a case with neurological anomalies

We report on a 22-week female fetus with multiple pterygia, congenital joint contractures, muscle hypoplasia, cystic hygroma, hydrops, pulmonary and cardiac hypoplasia, facial anomalies, and growth retardation. Examination also documented microcephaly, brain immaturity, and severe cerebellar and pontine hypoplasia with absence of the pyramidal tracts. The spinal cord showed a marked decrease in size of all white matter tracts. The muscles were markedly hypoplastic. The relation of the neurological findings to the development of the syndrome is discussed.

Lethal Pena-Shokeir 1 syndrome in three male siblings

A consanguineous family with no living children and three male siblings with Pena-Shokeir 1 syndrome is described. Two children died antepartum and the third shortly after delivery. The importance of early prenatal diagnosis, appropriate counseling and thorough evaluation of the neuromuscular system is discussed.

Lethal arthrogryposis multiplex congenita: a pathological study of 21 cases

Twenty-one cases of arthrogryposis multiplex congenita, which had resulted in death soon after birth or had been aborted following prenatal diagnosis, were studied. Histochemical and histological study of muscle indicated that 11 cases were of myogenic origin, including congenital muscular dystrophy in 10 cases from six families and nemaline rod myopathy in one. Neurogenic causation was established in five cases, including three with intra-uterine anoxic-ischaemic damage and two siblings with a severe form of cerebro-ocular-facio-skeletal syndrome. Causation remained uncertain in five. Unusual features included atrophy or amyoplasia of the diaphragm associated with lung hypoplasia in 10 cases and evidence of birth trauma in seven cases. One pair of siblings had subcutaneous tissue of doughy consistency and another pair had bladder hypertrophy. Familial recurrence was seen most often in cases with evidence of myogenic origin. We consider that neuropathology and muscle histochemistry are essential aids in determining the risks of recurrence in this group of lethal conditions which defy analysis by syndrome recognition techniques.

The lethal multiple pterygium syndrome: prenatal ultrasonographic and postmortem findings; a case report

In this report we present the prenatal ultrasonic and postmortem data of a male fetus of 25 weeks' gestational age with a lethal multiple pterygium syndrome. The importance of precise etiologic diagnosis in a midtrimester fetus with generalized edema and nuchal hygroma is emphasized.

Pathogenesis of the lethal multiple pterygium syndrome

We present autopsy studies in 4 unrelated fetuses with the lethal multiple pterygium syndrome (LMPS) with special emphasis on the neuromuscular system. The data suggest that LMPS combines the manifestations of a jugular lymphatic obstruction sequence with those of an early severe fetal akinesia sequence. The jugular lymphatic obstruction sequence with resultant edema and cystic hygroma colli causes fetal lethality usually in the second trimester of pregnancy. Generalized amyoplasia appears to be an important mechanism in the pathogenesis of fetal akinesia as part of LMPS and is not associated with dysgenesis or degeneration of the central nervous system (CNS) but is apparently the result of an early fetal muscular "dystrophy." We propose a genetically determined insult affecting the early embryonic development of both lymph vessels and muscles as the basic defect in LMPS. Placental structure, studied in all 4 cases, demonstrated that triploidy-like placental lesions are specific to LMPS. The present findings suggest that LMPS may be a less heterogeneous entity than previously proposed.