Majewski osteodysplastic primordial dwarfism type II (MOPD II): natural history and clinical findings

A description of the clinical features of Majewski osteodysplastic primordial dwarfism type II (MOPD II) is presented based on 58 affected individuals (27 from the literature and 31 previously unreported cases). The remarkable features of MOPD II are: severe intrauterine growth retardation (IUGR), severe postnatal growth retardation; relatively proportionate head size at birth which progresses to true and disproportionate microcephaly; progressive disproportion of the short stature secondary to shortening of the distal and middle segments of the limbs; a progressive bony dysplasia with metaphyseal changes in the limbs; epiphyseal delay; progressive loose-jointedness with occasional dislocation or subluxation of the knees, radial heads, and hips; unusual facial features including a prominent nose, eyes which appear prominent in infancy and early childhood, ears which are proportionate, mildly dysplastic and usually missing the lobule; a high squeaky voice; abnormally, small, and often dysplastic or missing dentition; a pleasant, outgoing, sociable personality; and autosomal recessive inheritance. Far-sightedness, scoliosis, unusual pigmentation, and truncal obesity often develop with time. Some individuals seem to have increased susceptibility to infections. A number of affected individuals have developed dilation of the CNS arteries variously described as aneurysms and Moya Moya disease. These vascular changes can be life threatening, even in early years because of rupture, CNS hemorrhage, and strokes. There is variability between affected individuals even within the same family.

Egg:embryo weight ratio as an indicator of dwarfism induced by infectious bronchitis virus

A simple objective method to quantify embryo dwarfism induced by infectious bronchitis virus in embryonated chicken eggs has been used to determine endpoints in virus titration and neutralization assays. The eggs and the respective embryos were weighed and embryo:egg weight (EE) ratios were calculated. The EE ratios were compared with the uninoculated control eggs and endpoints could be calculated objectively. EE indices were also calculated by dividing the EE ratios of inoculated embryonated chicken eggs by the mean EE ratio of uninoculated controls, or in the case of virus neutralization tests by the mean EE ratio of eggs inoculated with virus alone. Although this mean EE index did not reflect the dwarfing (or lack of it) in individual eggs, it served as a group indicator. This method would be useful to observe embryo lesions especially in field (non-egg adapted) infectious bronchitis virus isolates, which does not cause observable dwarfing until several embryo passages.

Short stature in beta-thalassemia minor subjects

BACKGROUND

Numerous disturbances in growth and development have been observed and demonstrated in homozygote beta-thalassemia patients. However, short stature in thalassemia minor subjects, who have a minor defect in hemoglobin chain synthesis, has not yet been studied.

MATERIAL/METHODS

In this cross-sectional study, the heights of 100 thalassemia minor subjects in the age group of 2-18 years and their parents were measured and analyzed. If the subject were in the 3-10 percentile range of height based on standardized sex and age curves, several follow-ups with complete history and physical examinations for a period of one year were preformed. If the healthy carrier's height was below the 3rd percentile, history, physical examination, and paraclinical examinations, including BUN, creatinine, electrolytes, serum alkaline phosphatase, thyroid function tests, growth hormone and cortisol levels, arterial blood gas, radiography of the left hand and wrist, etc, were also checked. One hundred healthy children were randomly chosen as a control group and matched for demographic characteristics with our healthy carrier subjects.

RESULTS

Mean +/- standard deviation for the age of our subjects was 6.62+/-3.63 years old. Twenty-seven (27%) of the patients had short stature. Except for hemoglobin (with a mean of 11.5 g/l), all other paraclinical data were normal.

CONCLUSIONS

We concluded that short stature was significantly more prevalent in the healthy beta thalassemia minor subjects than in the control group (p<0.001). Therefore, thalassemia minor can cause short stature.

Recent advances in Dyggve-Melchior-Clausen syndrome

Dyggve-Melchior-Clausen (DMC) is a rare autosomal-recessive disorder characterized by the association of a progressive spondylo-epi-metaphyseal dysplasia and mental retardation ranging from mild to severe. Electron microscopy studies of both DMC chondrocytes and fibroblasts reveal an enlarged endoplasmic reticulum network and a large number of intracytoplasmic membranous vesicles, suggesting that DMC syndrome may be a storage disorder. Indeed, DMC phenotype is often compared to that of type IV mucopolysaccharidosis (Morquio disease), a lysosomal disorder due to either N-acetylgalactosamine-6-sulphatase or beta-galactosidase deficiency. To date, however, the lysosomal pathway appears normal in DMC patients and biochemical analyses failed to reveal any enzymatic deficiency or accumulated substrate. Linkage studies using homozygosity mapping have led to the localization of the disease-causing gene on chromosome 18q21.1. The gene was recently identified as a novel transcript (Dym) encoding a 669-amino acid product (Dymeclin) with no known domains or function. Sixteen different Dym mutations have now been described in 21 unrelated families with at least five founder effects in Morocco, Lebanon, and Guam Island. Smith-MacCort syndrome (SMC), a rare variant of DMC syndrome without mental retardation, was shown to be allelic of DMC syndrome and to result from mutations in Dym that would be less deleterious to the brain. The present review focuses on clinical, radiological, and cellular features and evolution of DMC/SMC syndromes and discusses them with regard to identified Dym mutations and possible roles of the Dym gene product.

Dwarfism and impaired gut development in insulin-like growth factor II mRNA-binding protein 1-deficient mice

Insulin-like growth factor II mRNA-binding protein 1 (IMP1) belongs to a family of RNA-binding proteins implicated in mRNA localization, turnover, and translational control. Mouse IMP1 is expressed during early development, and an increase in expression occurs around embryonic day 12.5 (E12.5). To characterize the physiological role of IMP1, we generated IMP1-deficient mice carrying a gene trap insertion in the Imp1 gene. Imp1(-/-) mice were on average 40% smaller than wild-type and heterozygous sex-matched littermates. Growth retardation was apparent from E17.5 and remained permanent into adult life. Moreover, Imp1(-/-) mice exhibited high perinatal mortality, and only 50% were alive 3 days after birth. In contrast to most other organs, intestinal epithelial cells continue to express IMP1 postnatally, and Imp1(-/-) mice exhibited impaired development of the intestine, with small and misshapen villi and twisted colon crypts. Analysis of target mRNAs and global expression profiling at E12.5 indicated that Igf2 translation was downregulated, whereas the postnatal intestine showed reduced expression of transcripts encoding extracellular matrix components, such as galectin- 1, lumican, tenascin-C, procollagen transcripts, and the Hsp47 procollagen chaperone. Taken together, the results demonstrate that IMP1 is essential for normal growth and development. Moreover, IMP1 may facilitate intestinal morphogenesis via regulation of extracellular matrix formation.

La dysplasie métatropique : à propos de deux frères

Metatropic dwarfism is a rare heritable skeletal dysplasia. We report on two brothers, 4-month-old and 9-year-old, affected by the disease. Clinical and radiological features of the disease at different ages are discussed. Prenatal diagnosis is possible by ultrasonography. No treatment is available. Prevention by genetic counselling remains the principal possible assistance to high risk families.

Hydroxyapatite coating of external fixation pins to decrease axial deformity during tibial lengthening for short stature

BACKGROUND

Tibial valgus, a known complication of leg lengthening with external fixation techniques, has been related to the stability of the bone-fixator system and, in particular, to pin loosening. A hydroxyapatite coating has been reported to enhance the quality of the bone-pin interface. The aim of this study was to compare the prevalence of axial deformity after tibial lengthening with hydroxyapatite-coated external fixation pins with the prevalence after tibial lengthening with uncoated pins.

METHODS

We conducted a prospective study of thirty-four symmetrical tibial lengthening procedures in seventeen pathologically short patients. One limb of each patient was lengthened with use of hydroxyapatite-coated pins and the other, with standard uncoated pins; the sides of the operations were randomly selected. The bone angle in the frontal plane was measured before the operation and at the end of the fixation period, and the difference between these measurements was compared between the lengthening procedures performed with coated pins and those performed with uncoated pins.

RESULTS

The mean valgus deviation of the tibia was 6.5 degrees in the group treated with hydroxyapatite-coated pins and 12.5 degrees in the group treated with uncoated pins (p = 0.023). With the numbers available, other factors previously related to the development of valgus deformity did not differ significantly between the two groups.

CONCLUSION

Tibiae that are lengthened with the use of hydroxyapatite-coated external fixation pins are less prone to axial deviation in the frontal plane than are those treated with uncoated pins.

LEVEL OF EVIDENCE

Therapeutic study, Level I-1a (randomized controlled trial [significant difference]). See Instructions to Authors for a complete description of levels of evidence.

[The growth plate in chronic renal insufficiency]

Several alterations have been reported in the growth plate of young rats rendered uremic by subtotal nephrectomy, a widely used experimental model of growth failure secondary to renal insufficiency. In our lab's experience, uremia is associated with a markedly increased growth plate height which results from an elongation of the hypertrophic zone. These findings are not consistently observed in all studies, likely because of the different experimental conditions. Regardless of growth plate size, growth retardation induced by chronic renal failure is accompanied by an alteration of the dynamics of the growth plate with a decreased bone apposition rate at the metaphyseal end of growth cartilage and slower production and progression of chondrocytes from the resting zone up to the most distal hypertrophic zone adjacent to bone. These abnormal dynamics are associated with an irregular bone-cartilage interface and a disturbed process of chondrocyte maturation which becomes evident by a morphological criteria and by depressed expression of markers of chondrocyte maturation such as collagen X. The microscopic findings also suggest a disturbed process of capillary invasion, which precedes formation of new osseous tissue in the primary spongiosa, although the levels of vascular endothelial growth factor, as measured by immunohistochemistry, have been reported to be similar in the growth plate of uremic and control rats. The meaning of these findings in the pathogenesis of growth impairment secondary to chronic renal failure remains to be determined.

[Effect of growth hormone and calcitriol on the growth plate in uremic rats]

This study analyzed the modifications induced by growth hormone (GH) and/or calcitriol treatments in the growth plate of growth retarded uremic rats. Four groups of 5/6 nephrectomized rats were studied: untreated (U), treated with GH (U + GH), treated with calcitriol (U + D), treated with GH and calcitriol (U + GH + D). Treatments were given intraperitoneally during the second week of renal failure. Uremic groups were compared with sham-operated rats fed ad libitum (C) or pair-fed with U (CP). In comparison with C and CP, histomorphometric analysis of tibial proximal ends of U group showed decreased bone formation, as estimated by osseous front advance (OFA), elongation of growth cartilage and its hypertrophic zone, and decreased size of most distal chondrocytes. The U + D group tended to normalize growth cartilage height, and that of its hypertrophic zone, as well as the size of chondrocytes. In U + GH group OFA improved and chondrocyte size became normal, but growth cartilage remained elongated. Similar results were found in the U + GH + D group. These findings indicate that, in chronic renal insufficiency, the beneficial effect of GH on growth is not associated with normalization of growth cartilage morphology and that calcitriol facilitates chondrocyte maturation. When given together the effect of GH prevails.

Lower limb lengthening in turner dwarfism

The aim of this study was to review our cases of lower limb lengthening to treat Turner dwarfism, and to speculate whether or not effective limb lengthening can be achieved in this rare condition. Twelve tibiae and 2 femora were lengthened in 6 patients using the Ilizarov method for the tibia and a gradual elongation nail for the femur. The mean age at the time of surgery was 19 years, and the patients were followed up for a minimum of 2 years. The average gain in the tibial and femoral length was 6.2 cm and 6.0 cm, respectively. The average healing index of tibia and femur was 1.9 and 1.7 months. The average tibia-to-femur ratio improved from 0.68 preoperatively to 0.81 postoperatively, and leg-trunk ratios improved from 0.88 to 0.99. Seven segments (50.0 percent) had completed the lengthening protocol without complications. Two segments (14.3 percent) had an intractable pin site infection requiring a pin exchange, and four segments (35.7 percent) had twelve complications (a nonunion at the distraction site, premature consolidation, Achilles tendon contractures and planovalgus). The overall rate of complications was 100 percent for each bone lengthened. All the patients showing a nonunion at the distraction site had a reduced bone mass, which was less than 65 percent of those of the age-matched normal population. Despite the complications, all patients were satisfied with the results, and lower limb lengthening in Turner Dwarfism believed to be a valid option. However, it may require careful management in a specialist unit in order to prevent complications during the lengthening procedure. In addition, the osteopenia associated with an estrogen deficiency leading to problems in consolidation is a difficult issue to address.

Prenatal ultrasonographic diagnosis of diastrophic dysplasia at 13 weeks of gestation

Diastrophic dwarfism is a skeletal dysplasia that can be identified by ultrasound usually during the second trimester of pregnancy. This severe but non-lethal disorder of the cartilage can be diagnosed earlier using transvaginal sonography (TVS). We present a case of diastrophic dysplasia diagnosed at 13 weeks of gestation by TVS. The early TVS evaluation of the fetal biometric parameters and the accurate study of the morphological features of the fetal long bones and extremities allowed an early diagnosis of this rare pathology that leads to a progressive physical handicap, due mainly to severe kyphoscoliosis and arthropathies. Recently, the routine use of TVS at 11-14 weeks of gestation has permitted an earlier diagnosis to be reached of a great number of congenital anomalies. Patients at risk for skeletal dysplasia could benefit from the enhancements of ultrasound techniques. An early diagnosis of diastrophic dysplasia can be reached at the and of the first trimester of pregnancy, using TVS.

Pseudoachondroplasia is caused through both intra- and extracellular pathogenic pathways

Pseudoachondroplasia is a dominantly inherited chondrodysplasia associated with mutations in cartilage oligomeric matrix protein (COMP). Investigations into the pathogenesis of pseudoachondroplasia are hampered by its rarity. We developed a cell culture model by expressing mutant COMP in bovine primary chondrocytes using a gutless adenoviral vector. We show that mutant COMP exerts its deleterious effects through both intra- and extracellular pathogenic pathways. Overexpression of mutant COMP led to a dose-dependent decrease in cellular viability. The secretion of mutant COMP was markedly delayed, presumably due to a prolonged association with chaperones in the endoplasmic reticulum (ER). The ECM lacked organized collagen fibers and showed amorphous aggregates formed by mutant COMP. Thus, pseudoachondroplasia appears to be an ER storage disease, most likely caused by improper folding of mutant COMP. The growth failure of affected patients may be explained by an increased cell death of growth-plate chondrocytes. Dominant interference of the mutant protein on collagen fiber assembly could contribute to the observed failure of the ECM of cartilage and tendons.

Mesenteric inflammatory pseudotumor: unusual presentation with leukemoid reaction and massive calcified mass

The authors describe a child with an unusual presentation of mesenteric inflammatory pseudotumor in association with leukemoid reaction. An 11-year-old-boy admitted with short stature was found to have an abdominal mass localized in the right lower quadrant. The leukocyte count was 92,000/mm3 with neutrophilic leukemoid reaction. Abdominal ultrasonography and computed tomography revealed a massive calcified mass in the pelvis. Total resection of the mass was performed and the pathologic diagnosis of inflammatory pseudotumor of the mesentery was made. Leukemoid reaction dramatically resolved within a few days after surgical resection. Physicians should be aware of the association of inflammatory pseudotumor, leukemoid reaction, and massive calcification.

The diagnosis of skeletal dysplasias: a multidisciplinary approach

Skeletal dysplasias are heritable connective tissue disorders affecting skeletal morphogenesis and development. They represent a heterogeneous group of genetic disorders with more than 200 different entities being delineated to date. Because of this diversity, the diagnosis of a skeletal dysplasia is usually based on a combination of clinical, radiographic, morphologic, and, in some instances, biochemical and molecular studies. Tremendous advances have been made in the elucidation of the genetic defect of several of these conditions over the past 10 years. This progress has provided us with more insights into the genes controlling normal skeletal development. It also has opened new diagnostic perspectives. For several disorders, identification of the causal gene allows us now to confirm with a molecular test the diagnosis postulated on the basis of clinical, radiographic and/or morphologic studies. It also enables us to establish the diagnosis early in pregnancy. An accurate diagnosis is not only important for proper management of the affected individual but also the cornerstone for adequate genetic counseling.

[Dyggve-Melchior-Clausen syndrome: differential diagnosis of mucopolysaccharidosis type IV or Morquio disease]

Dyggve-Melchior-Clausen syndrome (DMCS) is an autosomal recessive skeletal dysplasia. Clinical and radiological similarities with Morquio's syndrome can initially lead wrongly to this diagnosis.

CASE REPORT

A nine-year-old boy had mental retardation and progressive postnatal dwarfism. Platyspondyly and dysplastic epiphyses and metaphyses resembled those of Morquio's disease; however, clinical and radiological data led to the diagnosis of DMCS.

CONCLUSION

Clinical and paraclinical features allowing the differentiation of Morquio's syndrome and DMCS are discussed. Initial clinical presentation may be similar, but the intellectual prognosis is different.

[MELAS syndrome masquerading as herpes encephalitis: genetic diagnosis]

INTRODUCTION

MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke like episodes) is a mitochondrial disease related to the mitochondrial DNA mutation. The tRNALeu(UUR) mutation at the base pair 3234 is associated to 80% of cases of MELAS syndrome. The onset with the stroke like episodes is often before the age 40. Herpes simplex encephalitis (HSE) presents as acute episodes of focal neurologic deficit that are often related to the temporal lobe. Occasionally MELAS syndrome and HSE may have a similar clinical presentation.

CLINICAL CASE

A 33-year-old woman presented with seizures and a right parietotemporal syndrome of acute onset. The differential diagnosis between HSE and MELAS syndrome was established. MELAS syndrome was suspected based on her phenotype. The diagnosis of MELAS syndrome was confirmed by the presence of the mitochondrial tRNALeu(UUR) mutation at the base pair 3243.

CONCLUSION

The clinical presentation of the MELAS syndrome may mimic that of the HSE, and antiviral treatment should be given until the diagnosis of MELAS syndrome is definitive. The study of the mitochondrial DNA helps diagnosing in a non invasive way many patients with MELAS syndrome.

Shwachman-Diamond syndrome in a Mexican family

Shwachman-Diamond Syndrome (SDS) is an inherited condition with multisystemic abnormalities including pancreatic exocrine dysfunction, neutropenia, short stature, and skeletal abnormalities. In this report, we describe the case of a 14-year-old female with a history of neutropenia, pancreatic exocrine insufficiency and pancreatic endocrine sufficiency, pancreatic lipomatosis (10), and the development of myeloid leukemia. Postmortem examination revealed a high probability of SDS. We also describe the clinical findings in the patient's six siblings, suggesting this as a familial form of SDS. Because the gene(s) responsible for this syndrome have not yet been identified, genetic confirmation is not yet possible. This is the first report in the literature of a Mexican family with probable SDS.

STAT1 mediates the increased apoptosis and reduced chondrocyte proliferation in mice overexpressing FGF2

Unregulated FGF receptor signaling results in bone malformations that affect both endochondral and intramembranous ossification, and is the basis for several genetic forms of human dwarfism. FGF signaling inhibits chondrocyte proliferation and we have previously shown that the transcription factor STAT1 mediates the growth inhibitory effect of FGF in vitro. We provide genetic evidence that STAT1 is a modulator of the negative regulation of bone growth by FGF in vivo. We crossed Stat1−/− mice with a transgenic mouse line overexpressing human FGF2 (TgFGF). TgFGF mice exhibit phenotypes characterized by chondrodysplasia and macrocephaly, which affect endochondral and intramembranous ossification. We found that the chondrodysplasic phenotype of these mice results both from reduced proliferation and increased apoptosis of growth plate chondrocytes. Loss of STAT1 function in TgFGF mice led to a significant correction of the chondrodysplasic phenotype, but did not affect the skull malformations. The reduced proliferation of TgFGF growth plate chondrocytes, as well as their excessive apoptosis, were restored to near-normal levels in the absence of STAT1 function. Unregulated FGF signaling in TgFGF mice also induced apoptosis in calvarial osteoblasts that was not, however, corrected by the absence of STAT1. Detailed analysis of Stat1−/− growth plates uncovered a transient phenotype, characterized by an expansion of the proliferative zone and by acceleration of longitudinal bone growth, that attenuated as the animals grew older. These results document an essential role for STAT1 in FGF-mediated regulation of cell growth that is specific to the epiphyseal growth plate.