Lipoatrophic-lipodystrophic syndromes: the spectrum of findings on MR imaging

Radiographic appearances of a continuous glucose monitor in a patient with lipodystrophy

We report the case of a 50-year old woman with a known history of lipodystrophy. A pelvic radiograph was taken for the investigation of right hip pain. The image shown demonstrates an indeterminate artefact projected over the right iliac fossa. A previous CT renal study was reviewed, demonstrating the same device in the subcutaneous tissues of the contralateral left lower quadrant which on close inspection was consistent with a continuous glucose monitoring device. Features of lipodystrophy were also noted on review of the CT imaging. Although many devices such as vagal stimulators and prosthetic valves are easily recognized by radiologists on radiographic images, they may be less familiar with devices such as continuous glucose monitors. The aim of this case report is to familiarize radiologists with the appearances of continuous glucose monitors to allow for effective reporting.

Severe insulin resistance syndromes

Severe insulin resistance syndromes are a heterogeneous group of rare disorders characterized by profound insulin resistance, substantial metabolic abnormalities, and a variety of clinical manifestations and complications. The etiology of these syndromes may be hereditary or acquired, due to defects in insulin potency and action, cellular responsiveness to insulin, and/or aberrations in adipose tissue function or development. Over the past decades, advances in medical technology, particularly in genomic technologies and genetic analyses, have provided insights into the underlying pathophysiological pathways and facilitated the more precise identification of several of these conditions. However, the exact cellular and molecular mechanisms of insulin resistance have not yet been fully elucidated for all syndromes. Moreover, in clinical practice, many of the syndromes are often misdiagnosed or underdiagnosed. The majority of these disorders associate with an increased risk of severe complications and mortality; thus, early identification and personalized clinical management are of the essence. This Review aims to categorize severe insulin resistance syndromes by disease process, including insulin receptor defects, signaling defects, and lipodystrophies. We also highlight several complex syndromes and emphasize the need to identify patients, investigate underlying disease mechanisms, and develop specific treatment regimens.

Not Just Fat: Imaging in Abdominal Fat Pathology

Fat in abdomen has diverse distribution and function. Insult to fat due to several causes can result in infarction or necrosis and present as acute abdomen clinically. Intra-abdominal focal fat infarction is one such condition that comprises of epiploic appendagitis, perigastric appendagitis, omental infarction, and torsion of fatty appendage of falciform ligament that have characteristic imaging features. Secondary causes of fat necrosis include pancreatitis or trauma related. Metabolic or responsive fat changes, like hypertrophy and dystrophy, can be diagnosed on imaging especially on computed tomography. Mesentric fat stranding including the mesentric panniculitis spectrum poses diagnostic dilemma and the causes and imaging role are covered in this review. Some infections and neoplasms that preferably affect abdominal fat compartments may mimic benign conditions, although some have specific patterns of involvement.

Visceral fat does not contribute to metabolic disease in lipodystrophy

OBJECTIVES

Lipodystrophies are characterized by regional or generalized loss of adipose tissue and severe metabolic complications. The role of visceral adipose tissue (VAT) in the development of metabolic derangements in lipodystrophy is unknown. The study aim was to investigate VAT contribution to metabolic disease in lipodystrophy versus healthy controls.

METHODS

Analysis of correlations between VAT volume and biomarkers of metabolic disease in 93 patients and 93 age/sex-matched healthy controls.

RESULTS

Patients with generalized lipodystrophy (n = 43) had lower VAT compared with matched controls, while those with partial lipodystrophy (n = 50) had higher VAT versus controls. Both groups with lipodystrophy had lower leg fat mass versus controls (p < 0.05 for all; unpaired t-test). In both generalized and partial lipodystrophy, there was no correlation between VAT and glucose, triglycerides or high-density lipoprotein cholesterol (p > 0.05 for all; Spearman correlation). In controls matched to patients with generalized or partial lipodystrophy, VAT correlated with glucose (R = 0.42 and 0.36), triglycerides (R = 0.36 and 0.60) and high-density lipoprotein cholesterol (R = -0.34 and -0.64) (p < 0.05 for all; Spearman correlation).

CONCLUSIONS

In contrast to healthy controls, metabolic derangements in lipodystrophy did not correlate with VAT volume. These data suggest that, in lipodystrophy, impaired peripheral subcutaneous fat deposition may exert a larger effect than VAT accumulation on the development of metabolic complications. Interventions aimed at increasing functional subcutaneous adipose tissue may provide metabolic benefit.

Barraquer-Simons Syndrome

BACKGROUND

Barraquer-Simons syndrome (BSS) is a rare acquired lipodystrophy characterized by gradually symmetric subcutaneous fat loss in a craniocaudal distribution, associated with hypocomplementemia, diabetes and hypertriglyceridemia. Few investigators have studied body fat distribution with cross-sectional imaging techniques.

METHODS

We present 2 cases of BSS with emphasis on phenotypic analysis through cross-sectional imaging.

RESULTS

For the first time, we demonstrate bone marrow involvement and deep cervical and axillary fat sparing of Barraquer-Simons using magnetic resonance imaging.

CONCLUSION

Phenotypic analysis in lipodystrophies such as Barraquer-Simons is an essential guide for future experiments. Therefore, careful analysis of cross-sectional imaging should be conducted in future studies as areas of involvement or fat sparing may be overlooked. The major contributions of our work are that this is the first time that deep cervical or nuchal and axillary fat sparing and bone marrow involvement has been documented in BSS.

Intra-abdominal fat. Part I. The images of the adipose tissue localized beyond organs

Unaltered fat is a permanent component of the abdominal cavity, even in slim individuals. Visceral adiposity is one of the important factors contributing to diabetes, cardiovascular diseases and certain neoplasms. Moreover, the adipose tissue is an important endocrine and immune organ of complex function both when normal and pathological. Its role in plastic surgery, reconstruction and transplantology is a separate issue. The adipose tissue has recently drawn the attention of research institutes owing to being a rich source of stem cells. This review, however, does not include these issues. The identification of fat is relatively easy using computed tomography and magnetic resonance imaging. It can be more difficult in an ultrasound examination for several reasons. The aim of this paper is to present various problems associated with US imaging of unaltered intra-abdominal fat located beyond organs. Based on the literature and experience, it has been demonstrated that the adipose tissue in the abdominal cavity has variable echogenicity, which primarily depends on the amount of extracellular fluid and the number of connective tissue septa, i.e. elements that potentiate the number of areas that reflect and scatter ultrasonic waves. The normal adipose tissue presents itself on a broad gray scale: from a hyperechoic area, through numerous structures of lower reflection intensity, to nearly anechoic regions mimicking the presence of pathological fluid collections. The features that facilitate proper identification of this tissue are: sharp margins, homogeneous structure, high compressibility under transducer pressure, no signs of infiltration of the surrounding structures and no signs of vascularization when examined with the color and power Doppler. The accumulation of fat tissue in the abdominal cavity can be generalized, regional or focal. The identification of the adipose tissue in the abdominal cavity using ultrasonography is not always easy. When in doubt, the diagnostic process should be extended to include computed tomography or magnetic resonance imaging, or sometimes biopsy (preferably the core-needle one).

What's the matter with MAT? Marrow adipose tissue, metabolism, and skeletal health

Marrow adipose tissue (MAT) is functionally distinct from both white and brown adipose tissue and can contribute to systemic and skeletal metabolism. MAT formation is a spatially and temporally defined developmental event, suggesting that MAT is an organ that serves important functions and, like other organs, can undergo pathologic change. The well-documented inverse relationship between MAT and bone mineral density has been interpreted to mean that MAT removal is a possible therapeutic target for osteoporosis. However, the bone and metabolic phenotypes of patients with lipodystrophy argues that retention of MAT may actually be beneficial in some circumstances. Furthermore, MAT may exist in two forms, regulated and constitutive, with divergent responses to hematopoietic and nutritional demands. In this review, we discuss the role of MAT in lipodystrophy, bone loss, and metabolism, and highlight our current understanding of this unique adipose tissue depot.

Imaging manifestations of abdominal fat necrosis and its mimics

Intraabdominal fat is a metabolically active tissue that may undergo necrosis through a number of mechanisms. Fat necrosis is a common finding at abdominal cross-sectional imaging, and it may cause abdominal pain, mimic findings of acute abdomen, or be asymptomatic and accompany other pathophysiologic processes. Common processes that are present in fat necrosis include torsion of an epiploic appendage, infarction of the greater omentum, and fat necrosis related to trauma or pancreatitis. In addition, other pathologic processes that involve fat may be visualized at computed tomography, including focal lipohypertrophy, pathologic fat paucity (lipodystrophies), and malignancies such as liposarcoma, which may mimic benign causes of fat stranding. Because fat necrosis and malignant processes such as liposarcoma and peritoneal carcinomatosis may mimic one another, knowledge of a patient's clinical history and prior imaging studies is essential for accurate diagnosis.

Altered metabolism and lipodystrophy in the early B-cell factor 1-deficient mouse

We previously reported that mice deficient for the transcription factor early B-cell factor (Ebf1) exhibit markedly increased numbers of osteoblasts, bone formation rate, and serum osteocalcin, but the bone marrow of Ebf1(-/-) mice is also striking in its increased marrow adiposity. The purpose of this work was to analyze the metabolic phenotype that accompanies the altered bone morphology of Ebf1(-/-) mice. Whereas marrow adiposity was increased, deposition of white adipose tissue in other regions of the body was severely reduced (sc 40-50%, abdominally 80-85%). Brown adipose exhibited decreased lipid deposition. Subcutaneous and perigonadal white adipose tissue showed a decrease in mRNA transcripts for peroxisomal proliferator-activated receptor-gamma2 and CCAAT/enhancer-binding protein-beta in Ebf1(-/-) tissue compared with wild type. Circulating levels of leptin were decreased in Ebf1(-/-) animals compared with their littermate controls (down 65-95%), whereas adiponectin remained comparable after 2 wk of age. Serum analysis also found the Ebf1(-/-) animals were hypoglycemic and hypotriglyceridemic. After ip injection of insulin, the serum glucose levels in Ebf1(-/-) mice took longer to recover, and after a glucose challenge the Ebf1(-/-) animals reached serum glucose levels almost twice that of their wild-type counterparts. Measurement of circulating pancreatic hormones revealed normal or reduced insulin levels in the Ebf1(-/-) mice, whereas glucagon was significantly increased (up 1.7- to 8.5-fold). Metabolically the Ebf1(-/-) mice had increased O(2) consumption, CO(2) production, food and water intake, and activity. Markers for gluconeogenesis, however, were decreased in the Ebf1(-/-) mice compared with controls. In conclusion, the Ebf1-deficient animals exhibit defects in adipose tissue deposition with increased marrow adiposity and impaired glucose mobilization.

Predictors of acquired lipodystrophy in juvenile-onset dermatomyositis and a gradient of severity

We describe the clinical features of 28 patients with juvenile dermatomyositis (JDM) and 1 patient with adult-onset dermatomyositis (DM), all of whom developed lipodystrophy (LD) that could be categorized into 1 of 3 phenotypes, generalized, partial, or focal, based on the pattern of fat loss distribution. LD onset was often delayed, beginning a median of 4.6 years after diagnosis of DM. Calcinosis, muscle atrophy, joint contractures, and facial rash were DM disease features found to be associated with LD. Panniculitis was associated with focal lipoatrophy while the anti-p155 autoantibody, a newly described myositis-associated autoantibody, was more associated with generalized LD. Specific LD features such as acanthosis nigricans, hirsutism, fat redistribution, and steatosis/nonalcoholic steatohepatitis were frequent in patients with LD, in a gradient of frequency and severity among the 3 sub-phenotypes. Metabolic studies frequently revealed insulin resistance and hypertriglyceridemia in patients with generalized and partial LD. Regional fat loss from the thighs, with relative sparing of fat loss from the medial thighs, was more frequent in generalized than in partial LD and absent from DM patients without LD. Cytokine polymorphisms, the C3 nephritic factor, insulin receptor antibodies, and lamin mutations did not appear to play a pathogenic role in the development of LD in our patients. LD is an under-recognized sequela of JDM, and certain DM patients with a severe, prolonged clinical course and a high frequency of calcinosis appear to be at greater risk for the development of this complication. High-risk JDM patients should be screened for metabolic abnormalities, which are common in generalized and partial LD and result in much of the LD-associated morbidity. Further study is warranted to investigate the pathogenesis of acquired LD in patients with DM.

Computed tomography findings of congenital generalized lipodystrophy: multiple nodular fatty liver and diffuse sclerosis of bones

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disease that is also referred to as Berardinelli-Seip syndrome. It is characterized by a lack of adipose tissue throughout the body from birth, muscular hypertrophy, advanced bone age, fatty liver, and insulin resistance. We describe computed tomography (CT) and magnetic resonance findings for a 35-year-old woman with CGL. Multiple nodular, well-defined regions of fatty infiltration of the liver are rare and have never been previously reported in a patient with lipodystrophy. To our knowledge, this is the first report describing CT findings of bone sclerotic changes associated with CGL.

Clinical features and metabolic and autoimmune derangements in acquired partial lipodystrophy: report of 35 cases and review of the literature

We describe clinical features, body fat distribution, and prevalence of metabolic abnormalities in 35 patients with acquired partial lipodystrophy (APL) seen by us over 8 years, and also review 220 cases of APL described in the literature. Based on the review and our experience, we propose that the essential diagnostic criterion for APL is the gradual onset of bilaterally symmetrical loss of subcutaneous fat from the face, neck, upper extremities, thorax, and abdomen, in the "cephalocaudal" sequence, sparing the lower extremities. Analysis of the pooled data revealed that female patients were affected approximately 4 times more often than males. The median age of the onset of lipodystrophy was 7 years. Several autoimmune diseases, in particular systemic lupus erythematosus and dermatomyositis, were associated with APL. The prevalence rates of diabetes mellitus and impaired glucose tolerance were 6.7% and 8.9%, respectively. Approximately 83% of APL patients had low complement (C) 3 levels and the presence of polyclonal immunoglobulin C3 nephritic factor. Twenty-two percent of patients developed membranoproliferative glomerulonephritis (MPGN) after a median of approximately 8 years following the onset of lipodystrophy. Compared with patients without renal disease, those with MPGN had earlier age of onset of lipodystrophy (12.6 +/- 10.3 yr vs 7.7 +/- 4.4 yr, respectively; p < 0.001) and a higher prevalence of C3 hypocomplementemia (78% vs 95%, respectively; p = 0.02). The pathogenesis of fat loss and MPGN in patients with APL remains unclear, but activation of an alternate complement pathway has been implicated. Treating the cosmetic disfigurement by surgical procedures has yielded inconsistent results. The use of thiazolidinediones to treat fat loss in patients with APL remains anecdotal. Prognosis is mainly determined by renal insufficiency due to MPGN.

Magnetic resonance imaging of congenital, inflammatory, and infectious soft-tissue lesions in children

Magnetic resonance imaging has the advantages of multiplanar capability and high degree of tissue differentiation. It is useful for assessing the extent of soft-tissue abnormalities, such as vascular malformations, inflammatory and infectious processes, muscle disorders, and limb hypertrophy. Magnetic resonance imaging is sensitive to the presence of water and edema and is a good indicator for early diagnosis of inflammation and its level of activity. Fat-saturation techniques, including T2-weighted sequences and inversion recovery imaging, optimize diagnostic accuracy. T1-weighted images are good at defining the distribution and proportion of fat in the body, so they are useful in evaluating syndromes of the limbs, including vascular malformations, as well as lipoatrophy-lipodystrophy conditions. Magnetic resonance imaging provides guidance for efficient tissue biopsy. It allows comprehensive pretherapeutic assessment of soft-tissue vascular anomalies. It constitutes a good modality for following up the natural history of soft-tissue disorders during childhood.