Diabetes mellitus among the Navajo. II. Plasma glucose and insulin responses.
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Biomedical subjects
Publications and source records attributed to D L Rimoin.
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A deficiency of human growth hormone not associated with other pituitary deficiencies was observed in midgets with sexual ateliosis, a form of dwarfism inherited as an autosomal recessive trait. Body proportions, sexual development, birth weight, and postpartum lactation are normal in this syndrome.
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This article reviews the newly described biochemical (type I and II collagen) abnormalities and specific gene defects in the skeletal dysplasias. The model of the collagen molecule is described and how collagen is processed from procollagen, where and how abnormalities occur, and the types of abnormalities produced (quantitative and qualitative). The only known type I collagen defects producing skeletal dysplasias--osteogenesis imperfecta, as well as the 'family' of established type II collagen disorders--achondrogenesis type II, hypochondrogenesis and spondyloepiphyseal dysplasia congenita are discussed. Finally, using case presentations, the practical approach to these disorders is shown. The importance of these investigations and the subsequent reevaluation of the clinical and radiological findings of specifically delineated skeletal dysplasias are discussed.
A retrospective study was done to determine the entire clinical spectrum of lumbar spine disease in 47 adult patients, averaging 27.6 years of age, with achondroplasia. Five distinct clinical categories were defined. Twenty-eight percent of the patients were asymptomatic; 28% had only mechanical or degenerative lumbar pain; 6% had symptoms of a disc herniation; 21% had spinal claudication; and 17% had spinal claudication and objective neurologic deficits. Over 50% of the achondroplastic patients in this series had minor or no lumbar-spine-related symptoms through the third decade. The number of symptomatic patients did not increase in the older age groups. Ninety-one percent of symptomatic patients were 30 years of age or younger at the onset of symptoms. The presence of a thoracolumbar kyphosis, regardless of its magnitude, an L1 interpediculate distance less than 20 mm, and L5 interpediculate distance less than 16 mm, and a large structural lumbar lordosis were found more frequently in patients with disabling symptoms.
The search for genetic markers has established that idiopathic diabetes mellitus is a genetically heterogeneous group of disorders that have glucose intolerance in common. The types of genetic markers--subclinical linkage, and association--and how they are utilized to delineate the genetic basis of the diabetic syndrome are discussed. The use of such markers as insulin levels, pancreatic islet cell antibodies, and HLA antigens has permitted the separation of insulin-dependent (juvenile) and not insulin-dependent (maturity) diabetes. Such studies have also started to reveal heterogeneity within these broad groups of insulin-dependent and not insulin-dependent types. This extensive heterogeneity has major implications for understanding the pathogenesis and genetics of diabetic mellitus and is of potentially great clinical significance, since the natural history and complications may well differ between these different disorders.
Ultrastructural abnormalities in bone and calcifying cartilage are presented for a recently identified lethal chondrodysplasia. Two siblings, aged 20 and 30 weeks of gestation, showed severe short-limb dwarfism and histologically distinct, highly disorganized masses of cartilage, bone, and mesenchymal tissue in the long bones. Regions of inappropriate cartilage calcification showed unusual, electron-dense, amorphous islands of mineralization and larger, less dense, layered calcified masses that occasionally entrapped chondrocytes. Bone abnormalities included abnormal cartilage-bone transition at the growth plate, general bone matrix disorganization due to irregularly oriented bundles of collagen, mineral crystals on the osteocyte lacunar rim, and accumulations of thickened collagen fibrils, also along the osteocyte lacunar rim. These findings point to abnormal calcification and mineralization distinct from those seen in other reported skeletal dysplasias. These abnormalities are associated with an anarchic distribution of mesenchymelike tissue infiltrating the cartilage and bone.
Mesomelic shortening of the extremities lends itself as a useful clinical and/or radiologic sign to characterize a group of hereditary bone dysplasias. Table 1 and Figure 4 are presented to facilitate the comparison between the many different types of mesomelic dwarfism. Differential diagnosis between these types is not difficult because of the specific bone changes and extraskeletal malformations present. As in many hereditary syndromes, however, there may be wide clinical variability within a single entity, and meticulous clinical and radiologic examination must be done to arrive at the correct diagnosis. Certain other forms of chondrodystrophies, such as achondroplasia, hypochondroplasia, pseudoachondroplasia and distrophic dwarfism, can be easily differentiated from the mesomelic dysplasias by their clinical features and skeletal radiographs. Nothing is known about the pathogenesis of the various forms of mesomelic dysplasias. There is no available specific treatment, although corrective surgery has benefited selected patients. The correct diagnosis is, however, important both for prognostication and accurate genetic counseling.
Metatropic dwarfism, the Kniest syndrome, and pseudoachondroplastic dysplasia are specific chondrodystrophic disorders that have in common dysplasia of the metaphyses, epiphyses, and vertebrae. Metatropic dwarfism and the Kniest syndrome have been confused with Morquio's disease and with each other in the past, but can be easily distinguished on the basis of radiographic features, clinical features, and cartilage pathology. The pseudoachondroplastic dysplasias are associated with short limbed dwarfism and have been confused with achondroplastic dwarfism, but can be readily distinguished on the basis of the normal head, delayed age of onset, the typical radiographic features and the cartilage pathology.
The majority of chondrodystrophies are associated with distinct abnormalities in chondro-osseous histopathology. In some disorders, the pathological abnormalities are characteristic and can be used as diagnostic criteria, in other instances the morphological abnormalities are not specific, and in still others, no abnormality in chondro-osseous morphology is present. In this paper, the chondro-osseous histopathology and ultrastructure of a number of chondrodystrophies are reviewed to illustrate the different pathogenetic mechanisms involved in each of these disorders.