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Case summary: A 6-month-old male entire domestic shorthair cat presented for presumptive Toxoplasma myopathy that was non-responsive to antiprotozoal therapy. Clinical features included marked macroglossia, dysphagia, regurgitation, truncal muscle hypertrophy, pelvic limb gait abnormalities and megaoesophagus. Relevant diagnostics included serial creatine kinase activity, cardiac troponin I, fluoroscopic swallow study and routine muscle histopathology. Ultimately, post-mortem histopathology with immunostaining demonstrated markedly decreased or absent staining for the rod and carboxy terminus of dystrophin, confirming a dystrophin-deficient muscular dystrophy (MD). The misdiagnosis of toxoplasmosis was based on an increased IgG titre and muscle histopathology submitted to a local laboratory. Treatment for megaoesophagus included vertical feeding of wet food only, sildenafil and omeprazole. Dysphagia and regurgitation improved moderately. Presumptive hyperaesthesia and muscle pain were managed with anti-inflammatory doses of prednisolone. The patient was ultimately euthanased as a result of progressive MD signs and uraemia at 2 years of age. Relevance and novel information: This case report highlights the collective clinical features of MD, as they could be considered pathognomonic for this rare condition and must be differentiated from other myopathies via specific immunostaining of muscle biopsies. This is crucial to obtain a correct and early diagnosis, allowing instigation of potentially valuable treatments. Megaoesophagus is an inconsistent feature in feline MD in addition to the more commonly observed oropharyngeal dysphagia. Management with a canned diet, sildenafil, omeprazole and upright feeding was beneficial with moderate improvement in the frequency of regurgitation. Prednisolone was thought to minimise the presumptive myalgia.

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Unilateral hypertrophy of the Tensor Fasciae Latae (TFL) muscle is a rare condition often characterized by a palpable mass in the lower limbs or hip pain. Despite its rarity, several causative factors have been identified, necessitating accurate diagnosis and appropriate management. Here, we present the case of a 53-year-old patient who sought outpatient consultation for a mass in the anterolateral aspect of the right thigh. Through this case study, we aim to contribute to the limited literature on this condition by discussing our diagnostic approach, management plan, and outcomes. Upon presentation, the patient underwent a thorough physical examination, revealing a non-tender, sessile mass seemingly originating in the deep connective tissue of the thigh. A magnetic resonance image (MRI) was performed to confirm the diagnosis and assess the extent of muscle involvement. This noninvasive modality provided valuable insights into the nature and localization of the mass, providing the diagnosis and guiding subsequent management decisions. Given the benign nature of the condition and absence of associated symptoms, conservative management was favored. Physical therapy focusing on stretching and strengthening exercises was initiated to address the underlying probable causes and improve functional capacity. Close monitoring through regular follow-up appointments was also recommended to track the progression of the hypertrophy and ensure symptomatic relief. Unilateral hypertrophy of the TFL muscle is a rare entity that presents diagnostic and management challenges. Through our case study, we have highlighted the importance of a comprehensive diagnostic workup, including imaging studies, in confirming the diagnosis and guiding management decisions. Conservative approaches, such as physical therapy, can effectively manage symptoms and improve quality of life in affected individuals. Continued research and documentation of cases are essential to expand our understanding of this condition and refine treatment strategies.

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Wooden Breast (WB) abnormality represents one of the major challenges that the poultry industry has faced in the last 10 years. Despite the enormous progress in understanding the mechanisms underlying WB, the precise initial causes remain to be clarified. In this scenario, the present research is intended to characterize the gene expression profiles of broiler Pectoralis major muscles affected by WB, comparing them to the unaffected counterpart, to provide new insights into the biological mechanisms underlying this defect and potentially identifying novel genes likely involved in its occurrence. To this purpose, data obtained in a previous study through the RNA-sequencing technology have been used to identify differentially expressed genes (DEGs) between 6 affected and 5 unaffected broilers' breast muscles, by using the newest reference genome assembly for Gallus gallus (GRCg7b). Also, to deeply investigate molecular and biological pathways involved in the WB progression, pathways analyses have been performed. The results achieved through the differential gene expression analysis mainly evidenced the downregulation of glycogen metabolic processes, gluconeogenesis, and tricarboxylic acid cycle in WB muscles, thus corroborating the evidence of a dysregulated energy metabolism characterizing breasts affected by this abnormality. Also, genes related to hypertrophic muscle growth have been identified as differentially expressed (e.g., WFIKKN1). Together with that, a downregulation of genes involved in mitochondrial biogenesis and functionality has been detected. Among them, PPARGC1A and PPARGC1B chicken genes are particularly noteworthy. These genes not only have essential roles in regulating mitochondrial biogenesis but also play pivotal roles in maintaining glucose and energy homeostasis. In view of that, their downregulation in WB-affected muscle may be considered as potentially related to both the mitochondrial dysfunction and altered glucose metabolism in WB muscles, and their key involvement in the molecular alterations characterizing this muscular abnormality might be hypothesized.

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For fresh meat consumers, eating satisfaction is of utmost importance and tenderness is one of the most important characteristics in this regard. Our study examined beef of different animal biotypes of the autochthonous breed "Asturiana de los Valles" (AV) to determine if early postmortem oxidative and proteolytic processes may influence the final tenderness of the product. This meat-specialized breed shows different biotypes depending on the frequency of a myostatin mutation "mh" that induces double-muscling or muscular hypertrophy (mh/mh, mh/+, +/+). Samples from the longissimus dorsi muscles of yearling bulls were analyzed during the first 24 h postmortem. Changes in the redox balance of muscle cells were significant in the first hours after slaughter; total antioxidant activity was higher in the mh/mh biotype and it followed the shortening of the sarcomeres, a key parameter in understanding meat tenderness. The two proteolytic systems studied (proteasome and lysosome) followed distinct patterns. Proteasome activity was higher in the (mh/+) biotype, which correlated with higher protein damage. Lysosome proteolysis was increased in the more tender biotypes (mh genotypes). Autophagic activation showed significant differences between the biotypes, with (mh/mh) showing more intense basal autophagy at the beginning of the postmortem period that decreased gradually (p < 0.001), while in the normal biotype (+/+), it was slightly delayed and then increased progressively (p < 0.001). These results suggest that this type of catalytic process and antioxidant activity could contribute to the earlier disintegration of the myofibers, particularly in the mh/mh biotypes, and influence the conversion of muscle into meat.

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Arterial entrapment syndrome (AES) at the elbow level is very rare. In cases of acute upper extremity ischaemia presenting in middle-aged patients with evident muscular hypertrophy, AES should always be included in the differential diagnosis. A thorough clinical examination should always follow, particularly when symptoms appear after reported strenuous upper extremity activity, and emergent surgical decompression is mandatory to avoid thrombotic complications in the affected arm in the future.

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Congenital muscular hypertrophy is a rare overgrowth disorder in the phosphatidylinositol-3-kinase related spectrum. In the past 3 years, ten patients with 11 limbs involved were treated in our centre. The aim of the study was to describe the clinical and radiological deformities of these patients. We documented the characteristic clinical morphological changes, such as hypertrophy, loss of wrist flexion, thumb hyperabduction, finger deviation and skin crease changes in the palm. Radiologically, the mean first metacarpal radial deviation angle of the affected side measured 55° (range 34 to 67) compared to the normal contralateral side 42° (range 32 to 53). The mean intermetacarpal space ratio was 1.2 (range 1.1 to 1.4) and the mean palm width ratio was 1.2 (range 1.1 to 1.3). In this study, we were able to further characterize the radiological and morphological changes of congenital muscular hypertrophy of upper limbs, which would be helpful for establishing the diagnosis and monitor treatment of this rare condition.Level of evidence: IV.

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The nematode C. elegans has been used widely to study the genetic and cellular basis of behavior. Yet the laboratory conditions under which it is typically studied offer only a narrow glimpse into the richness of natural behaviors this remarkable animal evolved over 500 million years of evolution. For example, burrowing behavior naturally occurs in the wild, but it remains understudied. Our group studies burrowing in an attempt to expand our understanding of the natural behavioral repertoire of C. elegans. Aside from being an interesting and tractable behavior, burrowing is experimentally useful and permits the titration of the muscular output exerted by C. elegans. Here we describe several burrowing assays that allow the modulation of muscular exertion. We used these to study both adaptive and pathological muscular processes such as muscle hypertrophy and dystrophy, respectively. We believe these assays will be of use for researchers studying the production of locomotion under normal and disease-challenged conditions.

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Segmental overgrowth of the skeletal muscles with bone involvement in body extremities, predominantly affecting the upper limb, is an extremely rare condition with only 40-50 affected children described clinically. The molecular pathogenesis of this disorder remains largely unclear except for the identification of a somatic PIK3CA mutation in each of the six patients genetically tested, all restricted to upper limbs in the literature. This study aimed to further characterize the molecular defects for patients affected with segmental overgrowth of the skeletal muscles by analyzing a 9-gene panel selected from the PI3K/AKT/mTOR pathway and genes associated with other related conditions. Nineteen unrelated patients were chosen for this study, comprising ten upper limb (nine unilateral and one bilateral) and nine lower limb (eight unilateral and one bilateral) cases with variable bone involvement. In each case, an activating PIK3CA mutation (p.E110del, p.N345K, p.E542K, p.E545K, p.H1047R, or p.H1047L) was identified in the affected muscle tissue with variant allele frequencies ranging from 13.88 to 30.43%, while no mutation was detected in the paired peripheral blood sample, indicating somatic mosaicism. All detected mutations were limited to PIK3CA and were previously reported in other overgrowth syndromes currently categorized under the PIK3CA-Related Overgrowth Spectrum (PROS). Our study provides strong molecular evidence that isolated segmental overgrowth of the skeletal muscle with bone involvement is a subtype of PROS. Our findings expand the PROS clinical presentations with a newly molecularly classified condition and can provide guidance in clinical and molecular diagnosis and treatment for patients with this condition.

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A prescrição de exercícios físicos em intensidades moderada e alta, para indivíduos obesos, pode induzir maiores percepções de desconforto/desprazer e, consequentemente, desencorajá-los a aderir a uma rotina de exercícios físicos. O objetivo deste trabalho foi investigar os efeitos de um programa de treinamento de força com intensidade autosselecionada, na composição corporal, hipertrofia e qualidade do sono de uma voluntária recémsubmetida a cirurgia bariátrica (idade: 28 anos; altura: 158cm; peso: 69 kg; índice de massa corporal: 27,64). A voluntária realizou um programa de treinamento de força com intensidade autosselecionada, pelo período de oito semanas (2 sessões semanais). Foi avaliada a qualidade de sono, por meio do questionário Pittsburgh sleep quality index; a composição corporal, por absorciometria de feixe duplo; e, a espessura muscular e do tecido adiposo, por ultrassonografia; antes e após a intervenção. Antes e após as sessões de treinamento, a percepção de prazer/desprazer foi mensurada com o auxílio de uma escala de valência afetiva. O programa de exercícios com intensidade autosselecionada resultou em uma diminuição de 2% no percentual de gordura, e de 7% na massa corporal total; sem modificação para a massa livre de gordura. Houve redução de 22% na espessura do tecido adiposo, e de 11% na espessura muscular do bíceps braquial; de 28% na espessura do tecido adiposo, e de 4% na espessura muscular do vasto lateral. A voluntária reportou percepção de prazer/desprazer positiva na maioria das sessões. No entanto, não houve diferença significativa entre os resultados para qualidade de sono. O treinamento com intensidade autosselecionada promoveu respostas positivas, relacionadas à percepção de prazer/desprazer, além de favorecer uma tendência à perda significativa de massa corporal total, sem prejuízos para a massa magra.(AU)

The prescription of physical exercise in moderate and high intensities for obese individuals may induce greater perceptions of discomfort/displeasure, consequently, decline adherence to a physical exercise routine. The objective of this study was investigate the effects of a strength training program with self-selected intensity, body composition, hypertrophy and sleep quality of a participant recently bariatric surgery (age: 28 years; height: 158cm; weight: 69 kg; body mass index: 27.64). The participant performed a strength training program with self-selection intensity, for a period of eight weeks (2 weekly sessions). Sleep quality was evaluated using the Pittsburgh sleep quality index questionnaire; body composition, by dual-energy x-ray absorptiometry, muscle and adipose tissue thickness by ultrasound. Each measure was before and after the intervention. Before and after the training sessions, the perception of pleasure/displeasure was measured with the affective valence scale. The exercise program with self-selected intensity resulted in a 2% decrease in fat percentage, and 7% in total body mass; without modification to the fat-free mass. Yet, there was a reduction of 22% in the thickness of adipose tissue, and 11% in the muscle thickness of the brachial biceps; 28% in the thickness of adipose tissue, and 4% in the muscle thickness of the vastus lateralis. The participant reported a perception of positive pleasure in most sessions. However, there was no significant difference between the results for sleep quality. The training with self-selected intensity promoted positive responses, related to the perception of pleasure/displeasure, besides promote a tendency to significant loss of total body mass, without damage to lean mass. (AU)

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Hereditary myotonia (HM) is a genetic disorder that occurs due to mutations in the chloride channel and results in delayed relaxation of the skeletal muscles. HM has been described in 12 dog breeds, and in five of them, molecular studies of this disorder were performed and mutations in the CLCN1 gene were described. In this study, an affected American Bulldog with HM clinically characterized by muscle hypertrophy, myotonic discharges, and nondystrophic myotonia with a "warm-up" phenomenon was evaluated, and the candidate canine CLCN1 gene was sequenced. The molecular analysis revealed a frameshift mutation NM_001003124.2:c.436_437insCTCT that resulted in a frameshift and a premature stop codon NP_001003124.1:pTyr146SerfsTer49 . Two aberrant alternative CLCN1 transcripts were observed in an affected dog, the expected transcript with the 4 bp insertion, NM_001003124.2:r.436_437insctct, and an unexpected transcript containing parts of intron 6 in addition to the insertion in exon 4, NM_001003124.2:[r.436_437insctct;r.774_775ins79]. In conclusion, the frameshift mutation in the CLCN1 gene is associated with autosomal recessive HM in American Bulldog and this study constitutes the first description of the disease in this breed.

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Blood flow restriction (BFR) training has been shown to induce favorable changes in muscle mass and strength with a considerably low training load (20 - 30% 1RM). However, it has never been evaluated if an additional post-exercise protein supplementation enhances the effects of this training regimen. Thirty healthy older men (60.1 ± 7.6 years) were enrolled in the 8-week intervention and randomly allocated to one of the following groups: low-load BFR training with protein (collagen hydrolysate) supplementation (BFR-CH), low-load BFR training with placebo (BFR-PLA), or a control group without training, but with protein supplementation (CON). Muscle cross-sectional area (CSA), muscle strength, circulating reactive oxygen species and IGF-1 were measured before and after the intervention. Muscle CSA increased in both BFR-CH and BFR-PLA groups by 6.7 ± 3.2 % (p < 0.001) and 5.7 ± 2.7 % (p < 0.001) respectively. No significant changes were observed in the CON group (1.1 ± 1.7 %, p = 0.124). Evaluation of isometric strength (p = 0.247), insulin-like growth factor 1 (p = 0.705) and the production of reactive oxygen species (pt1 = 0.229; pt2 = 0.741) revealed no significant interaction effect but a significant long-term time effect (p < 0.001). Our results demonstrate that BFR training is an effective alternative for increasing muscle CSA in older men. Although there was a trend towards greater muscle mass adaptations in the BFR-CH group, these findings showed no statistical significance. Further research with larger sample sizes is needed to confirm these results.

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PIK3CA-related overgrowth spectrum is a group of rare genetic disorders with asymmetric overgrowth caused by somatic mosaic PIK3CA mutations. Here, we report clinical data and molecular findings from two patients with congenital muscular upper limb overgrowth and aberrant anatomy. During debulking surgery, numerous ectopic muscles were found in the upper limbs of the patients. DNA sequencing, followed by digital polymerase chain reaction, was performed on DNA extracted from biopsies from hypertrophic ectopic muscles and identified the somatic mosaic PIK3CA hotspot mutations c.3140A > G, p.(His1047Arg) and c.1624G > A, p.(Glu542Lys) in a male (patient 1) and a female (patient 2) patient, respectively. Patient 1 had four ectopic muscles and unilateral isolated muscular overgrowth while patient 2 had 13 ectopic muscles and bilateral isolated muscular overgrowth of both upper limbs, indicating that her mutation occurred at early pre-somitic mesoderm state. The finding of PIK3CA mutations in ectopic muscles highlights the importance of PIK3CA in cell fate in early human embryonic development. Moreover, our findings provide evidence that the disease phenotype depends on the timing of PIK3CA mutagenesis during embryogenesis and confirm the diagnostic entity PIK3CA-related muscular overgrowth with ectopic accessory muscles.

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Acquired outpouches of the intestinal tract are referred to as pseudodiverticula or false pulsion diverticula. In contrast to true diverticula, in which the wall contains all layers of the intestinal tract, the wall of pseudodiverticula lacks the tunica muscularis. Smooth muscle hypertrophy of the small intestine is commonly considered a cause of pseudodiverticulosis in animals due to increased intraluminal pressure. This study reports pseudodiverticula associated with idiopathic smooth muscle hypertrophy of the small intestine in lagomorphs. Four domestic rabbits had single or multiple (up to 200) pseudodiverticula of various size in the small intestine. In all cases the tunica muscularis was diffusely thickened, significantly exceeding reference thickness of 14 rabbits (mean, 112.3 µm; range, 26.3-389.0 µm). Clinical signs were considered to be caused by severe necrosis and inflammation of the wall of large pseudodiverticula, leading to perforation with subsequent peritonitis and mesenteric and omental abscess formation in 2 cases.

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Congenital muscle hypertrophy of the upper limb is a very rare condition with unknown aetiology. This descriptive observational and retrospective series included eight children followed by a multidisciplinary team from 2005 to 2017. The diagnosis was based on a cluster of clinical and radiological characteristics after elimination of differential diagnoses. Patients were categorized according to: anomalies of the wrist, anomalies of long fingers of intrinsic or extrinsic origin; and anomalies of the thumb with or without first web space contracture. Treatment begins in young children with hand orthoses to limit muscle contraction and joint malposition. The purpose of surgical treatment was to release contractures and to restore muscle balance through, in the main, finger intrinsic releases and first web releases. At the 2-year follow-up, we found that limited surgical procedures improved finger, thumb and wrist positions. We conclude that muscle hypertrophy is the main cause of deformity and that selective releases of contracted musculo-tendinous units and skin lengthening are effective. LEVEL OF EVIDENCE: IV.

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As double-muscled Belgian Blue (BB) and Piemontese (PIEM) breeds are heavily selected for different objectives (the former mainly for muscularity, the latter for ease of calving), the aim of this study was to compare sexual dimorphism in 56 crossbred young bulls and heifers obtained from dairy cows mated to bulls of the two beef breeds. Young PIEM- and BB-sired bulls had similar fattening performances and beef traits, although the BB crossbreds were slightly more muscular. Otherwise, the BB-sired heifers exceeded the PIEM-sired heifers in growth rate (1.12 vs. 0.98kg/d), feed efficiency (0.129 vs. 0.121kg/kg DM), increases in muscle scores (1.45 vs. 0.98 SEUROP scores) and carcass yield (0.612 vs. 0.605), but not in fatness, retail cut proportions and meat quality traits. Sexual dimorphism is, therefore, less distinct in BB than in PIEM crossbreds. In conclusion, BB sires are to be preferred for "product quality", and PIEM sires for "process quality", on account of welfare and ethical issues.

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The incidence of idiopathic muscular hypertrophy of oesophagus (IMHE) is low, and <100 cases of IMHE have been reported. IMHE is a benign oesophageal disease, characterised by hyperplasia of all layers of the wall and in particular, muscle layer. Only a few cases have been reported regarding its clinical symptoms and images. In this present case, we report a cardia cancer with IMHE, showing significant hypertrophy of muscular layer of middle part of the oesophagus and successfully treated with minimally invasive thoracoscopic surgery.

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BACKGROUND: Resistance training (RT) for upper body muscle hypertrophy (UBMH) typically entails high volumes of sets per muscle group per training session. The majority of RT regimens does not discriminate between upper and lower body muscle groups, while these groups may respond differently to RT set volumes in terms of maximum skeletal muscle mass gain. Recent studies have examined the effect of different set volumes on the extent of UBMH to formulate optimal RT regimens and to make RT programmes more time-efficient. OBJECTIVE: To analyse the effect of the number of RT sets on the extent of UBMH on the basis of recent literature. RESULTS AND CONCLUSION: The analysis suggests that, statistically, high set volumes (≥3) are not significantly better than low set volumes (<3) in regard to UBMH in untrained subjects. For trained subjects, the literature is lacking in well-designed studies comparing low and high training volumes, as well as analysing upper and lower body muscles separately. Therefore, it is not possible to conclude that high volume of sets offers better results than low volume of sets for UBMH, and vice versa.

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Objetivo: Buscar sistematicamente na literatura evidências de hipertrofia muscular em pessoas idosas por meio do treinamento de resistência. Métodos: Trata-se de uma revisão sistemática de literatura levando em consideração os preceitos do PRISMA. Consultaram-se os bancos de dados Pubmed, Scielo e Pedro nos idiomas português e inglês, por meio dos descritores: idoso, envelhecimento, ganho de massa muscular e hipertrofia muscular. Resultados: Não ocorreram estudos na plataforma Scielo, e após filtro com base nos critérios de inclusão e exclusão obtiveram-se 24 estudos. Os estudos demonstram que é possível melhorar a massa muscular em treinamento de resistência em idosos, uma vez que os exercícios apresentem a dose correta: intensidade, volume, carga apropriada, utilizando uma investigação sensível. Conclusão: Sugere-se que para hipertrofia muscular em idosos, os protocolos de treinamento resistidos tenham em média 12 semanas de treinamento, com frequência de duas a três vezes por semana, que apresentem cinco exercícios realizados em três séries de oito a 12 repetições e cargas superiores a 60% 1RM para que ocorra a hipertrofia muscular. (AU)

Objective: To systematically seek evidence in the literature for muscular hypertrophy in older people through resistance training. Methods: This is a systematic review of literature taking into account the precepts of PRISMA. The Pubmed, Scielo and Pedro databases were consulted in the Portuguese and English languages, using the descriptors: elderly, aging, muscle mass gain and muscle hypertrophy. Results: There were no studies in the Scielo platform, after filtering based on the inclusion and exclusion criteria, 24 studies were obtained. It show that is possible to improve muscle mass in endurance training in the elderly, once the exercises present the correct dose: intensity, volume, appropriate load, using a sensitive investigation. Conclusion: It is suggested that for muscular hypertrophy in the elderly, the resistance training protocols have, on average, 12 weeks of training, two to three times a week, with five exercises performed in three sets of eight to 12 repetitions and higher loads to 60% 1RM for muscle hypertrophy to occur. (AU)

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As a widely distributed and natural existing antioxidant, ferulic acid and its functions have been extensively studied in recent decades. In the present study, hypertrophic growth of fast skeletal myofibers was observed in adult zebrafish after ferulic acid administration for 30 days, being reflected in increased body weight, body mass index (BMI), and muscle mass, along with an enlarged cross-sectional area of myofibers. qRT-PCR analyses demonstrated the up-regulation of relative mRNA expression levels of myogenic transcriptional factors (MyoD, myogenin and serum response factor (SRF)) and their target genes encoding sarcomeric unit proteins involved in muscular hypertrophy (skeletal alpha-actin, myosin heavy chain, tropomyosin, and troponin I). Western blot analyses detected a higher phosphorylated level of zTOR (zebrafish target of rapamycin), p70S6K, and 4E-BP1, which suggests an enhanced translation efficiency and protein synthesis capacity of fast skeletal muscle myofibers. These changes in transcription and translation finally converge and lead to higher protein contents in myofibers, as confirmed by elevated levels of myosin heavy chain (MyHC), and an increased muscle mass. To the best of our knowledge, these findings have been reported for the first time in vivo and suggest potential applications of ferulic acid as functional food additives and dietary supplements owing to its ability to promote muscle growth.

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BACKGROUND: The simplistically and ambiguously termed 'fibrostenosis' of bowel is a hallmark of severe Crohn's disease [CD] and a major contributor to medical treatment failure. Non-invasive imaging assessment and novel medical therapy targeting this condition are under investigation, which particularly requires a better understanding of the underlying histological basis. METHODS: We analysed 48 patients with stricturing Crohn's ileitis or/and colitis that required surgical resection. The most representative sections of the fibrostenotic, non-stenotic and uninvolved regions were reviewed for histological analysis. For each layer of bowel wall (mucosa including muscularis mucosae [MU], submucosa [SM], muscularis propria [MP], subserosal adventitia [SS]), histological abnormalities were evaluated individually, including active and chronic inflammation, fibrosis, smooth muscle hyperplasia or hypertrophy, neuronal hypertrophy and adipocyte proliferation. A novel semiquantitative histological grading scheme was created. RESULTS: The most significant histopathological features characterizing the stricturing intestines were smooth muscle hyperplasia of SM, hypertrophy of MP and chronic inflammation. The muscular alteration was predominant in all layers. The overall muscular hyperplasia/hypertrophy was positively correlated with chronic inflammation and negatively correlated with fibrosis, whereas SM muscular hyperplasia was also associated with MU active inflammation. Similar changes, to a lesser extent, occurred in the adjacent non-stenotic inflamed bowel as well. CONCLUSIONS: In CD-associated 'fibrostenosis', it is the smooth muscle hyperplasia/hypertrophy that contributes most to the stricturing phenotype, whereas fibrosis is less significant. The 'inflammation-smooth muscle hyperplasia axis' may be the most important in the pathogenesis of Crohn's strictures.

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