Pseudohyperkalemia in horses with rhabdomyolysis reported by an enzymatic chemistry analyzer.

OBJECTIVE: To investigate pseudohyperkalemia occurring in horses experiencing rhabdomyolysis when serum chemistry profiles are run on an VetScan VS2 analyzer (Abaxis). ANIMALS: 18 horses with rhabdomyolysis (creatine kinase [CK] > 1,000 U/L). METHODS: In 3 horses with serum CK activities > 5,800 U/L and persistent serum potassium concentrations of > 8.5 mmol/L (VetScan VS2), potassium concentrations were reevaluated with either i-STAT Alinity Base Station (Abbott), Catalyst (Idexx), or Cobas c501 (Roche) ion-specific analyzers. Paired serum samples from 15 additional horses (median serum CK activity, 7,601 U/L; range, 1,134 to 192,447 U/L) were analyzed on both VetScan VS2 and Cobas c501 machines. Serum potassium concentrations were compared between the VetScan VS2 and ion-specific analyzers by Bland-Altman and Wilcoxon ranked tests and correlated to log10 CK activity via Pearson correlation. RESULTS: Serum potassium concentrations were significantly higher on the VetScan VS2 (6.7 ± 1.6 mmol/L) versus the ion-specific analyzers (4.0 ± 1.1 mmol/L; P < .0001), with high bias shown in Bland-Altman analysis (43.1 ± 27.9). Potassium concentrations positively correlated with log10 CK activity with the VetScan VS2 (R2 = 0.51; P = .003) but not the Cobas (R2 = 0.09; P = .3) analyzer. CLINICAL RELEVANCE: An alternate analyzer to the VetScan VS2 should be used to evaluate serum potassium concentrations in horses with rhabdomyolysis because the VetScan VS2 methodology uses lactate dehydrogenase, which increases in serum with rhabdomyolysis and falsely elevates potassium concentrations.

Cook Inlet beluga whale Delphinapterus leucas with valvular endocarditis, encephalitis, rhabdomyolysis, heavy parasitism and fungal dermatitis.

This is a case report of a Cook Inlet beluga whale Delphinapterus leucas found dead stranded on September 28, 2020 in Turnagain Arm, Alaska. This subadult male had valvular endocarditis, encephalitis, rhabdomyolysis, myoglobinuric nephropathy, severe parasitism and fungal dermatitis. Erysipelothrix rhusiopathiae was detected in the heart lesion, eye and external swabs. The level of infection and parasitism in this individual is markedly higher than what has been found in other Cook Inlet belugas, suggesting immunosuppression.

The pathophysiology of rhabdomyolysis in ungulates and rats: towards the development of a rodent model of capture myopathy.

Capture myopathy (CM), which is associated with the capture and translocation of wildlife, is a life-threatening condition that causes noteworthy morbidity and mortality in captured animals. Such wildlife deaths have a significant impact on nature conservation efforts and the socio-economic wellbeing of communities reliant on ecotourism. Several strategies are used to minimise the adverse consequences associated with wildlife capture, especially in ungulates, but no successful preventative or curative measures have yet been developed. The primary cause of death in wild animals diagnosed with CM stems from kidney or multiple organ failure as secondary complications to capture-induced rhabdomyolysis. Ergo, the development of accurate and robust model frameworks is vital to improve our understanding of CM. Still, since CM-related complications are borne from biological and behavioural factors that may be unique to wildlife, e.g. skeletal muscle architecture or flighty nature, certain differences between the physiology and stress responses of wildlife and rodents need consideration in such endeavours. Therefore, the purpose of this review is to summarise some of the major etiological and pathological mechanisms of the condition as it is observed in wildlife and what is currently known of CM-like syndromes, i.e. rhabdomyolysis, in laboratory rats. Additionally, we will highlight some key aspects for consideration in the development and application of potential future rodent models.

Rhabdomyolysis and myoglobinuria following single induction dose of propofol in a dog.

OBJECTIVE: To report a case of rhabdomyolysis and myoglobinuria following single induction dose of propofol in a dog. CASE SUMMARY: A 5-year-old intact male Shih-Tzu dog was presented for pigmenturia occurring a few hours following anesthesia for comprehensive oral health assessment and treatment. After premedication with IV diazepam (0.5 mg/kg), anesthesia was induced with IV propofol (4 mg/kg) and maintained with isoflurane vaporized in oxygen. A few hours following recovery from anesthesia, the dog developed rhabdomyolysis and myoglobinuria associated with increased serum alanine aminotransferase and C-reactive protein concentrations, as well as mild hypokalemia and euglycemic glycosuria. Approximately 48 hours after IV fluid therapy, the dog was clinically normal, and myoglobinuria progressively resolved. NEW OR UNIQUE INFORMATION PROVIDED: This is the first case description of rhabdomyolysis and myoglobinuria following a single dose of injectable propofol.

Type 2 polysaccharide storage myopathy in Quarter Horses is a novel glycogen storage disease causing exertional rhabdomyolysis.

BACKGROUND: Both type 1 (PSSM1) and type 2 polysaccharide storage myopathy (PSSM2) are characterised by aggregates of abnormal polysaccharide in skeletal muscle. Whereas the genetic basis for PSSM1 is known (R309H GYS1), the cause of PSSM2 in Quarter Horses (PSSM2-QH) is unknown and glycogen concentrations not defined. OBJECTIVES: To characterise the histopathological and biochemical features of PSSM2-QH and determine if an associated monogenic variant exists in genes known to cause glycogenosis. STUDY DESIGN: Retrospective case control. METHODS: Sixty-four PSSM2-QH, 30 PSSM1-QH and 185 control-QH were identified from a biopsy repository and clinical data, histopathology scores (0-3), glycogen concentrations and selected glycolytic enzyme activities compared. Coding sequences of 12 genes associated with muscle glycogenoses were identified from whole genome sequences and compared between seven PSSM2-QH and five control-QH. RESULTS: Exertional rhabdomyolysis in PSSM2-QH occurred predominantly in barrel racing and working cow/roping performance types and improved with regular exercise and a low starch/fat-supplemented diet. Histopathological scores, including the amount of amylase-resistant polysaccharide (PSSM2-QH 1.4 ± 0.6, PSSM1-QH 2.1 ± 0.3, control-QH 0 ± 0, p < 0.001), and glycogen concentrations (PSSM2-QH 129 ± 62, PSSM1-QH 175 ± 9, control-QH 80 ± 27 mmol/kg, p < 0.0001) were intermediate in PSSM2-QH with significant differences among groups. In PSSM2-QH, abnormal polysaccharide had a less filamentous ultrastructure than PSSM1-QH and phosphorylase and phosphofructokinase activities were normal. Seventeen of 30 PSSM2-QH with available pedigrees descended from one of three stallions within four generations. Of the 29 predicted high or moderate impact genetic variants identified in candidate genes, none were present in only PSSM2-QH and absent in control-QH. MAIN LIMITATIONS: Analyses of PSSM2-QH and PSSM1-QH were performed on shipped samples, controls on frozen samples. CONCLUSIONS: PSSM2-QH is a novel glycogen storage disorder that is not the result of a mutation in genes currently known to cause muscle glycogenoses in other species.

CONTEXTO: Ambos os tipos 1 e 2 de miopatia por acúmulo de polissacarídeo (PSSM) são caracterizados por agregados de polissacarídeos anormais no músculo esquelético. Enquanto a base genética do PSSM 1 é conhecida (R309H GYS1), a causa do PSSM2 em cavalos Quarto de Milha (PSSM2-QH) é desconhecida, e a concentração de glicogênio não é definida. OBJETIVOS: Identificar as características histopatológicas e bioquímicas do PSSM-QH e determinar se há uma variante monogênica em genes conhecidos por causar glicogenose. DELINEAMENTO DO ESTUDO: Caso controlado retrospectivo. METODOLOGIA: 64 PSSM2-QH, 30 PSSM1-QH e 185 QH controles foram identificados em um arquivo de dados. Informação clínica, achados histológicos (escala 0-3), concentração de glicogênio e atividade enzimática de algumas enzimas glicolíticas foram comparadas. Sequências codificadas de 12 genes associados com glicogenose muscular foram identificados nas sequências genômicas completas, e comparadas entre 7 PSSM2-QH e 5 QH controles. RESULTADOS: Rabdomiólise por exercício em PSSM2-QH ocorreu predominantemente em cavalos de corrida de tambor e cavalos de team roping/trabalho com gado, e melhorou com exercício regular e uma dieta com baixo amido e alta gordura. A escala histopatológica, incluindo a quantidade de polissacarídeos resistentes à amilase (PSSM2-QH 1.4 ± 0.6, PSSM1-QH 2.1 ± 0.3, controle-QH 0 ± 0, P < 0.001), e concentrações de glicogênio (PSSM2-QH 129 ± 62, PSSM1-QH 175 ± 9, controle-QH 80 ± 27 mmol/kg, P < 0.0001) foram intermediárias em PSSM2-QH com diferença significante entre grupos. Em PSSM2-QH, polissacarídeo anormal teve uma ultraestrutura menos filamentosa do que PSSM1-QH e as atividades de fosforilase e fosfofrutoquinase foram normais. Dezessete dos 30 PSSM2-QH com pedigree disponível descendiam de 1 de 3 garanhões dentro de 4 gerações. Das 29 variações genéticas preditas a terem impacto moderado ou alto como genes candidatos, nenhuma estava presente apenas em PSSM2-QH e ausente no grupo controle-QH. PRINCIPAIS LIMITAÇÕES: As análises feitas nas amostras de PSSM2-QH e PSSM1-QH foram realizadas em amostras enviadas por correio, e as amostras dos animais controles eram amostras congeladas. CONCLUSÕES: PSSM2-QH é uma nova doença por acúmulo de glicogênio que não é o resultado de uma mutação nos genes conhecidos por causarem glicogenose muscular em outras espécies.

Enriched Pathways of Calcium Regulation, Cellular/Oxidative Stress, Inflammation, and Cell Proliferation Characterize Gluteal Muscle of Standardbred Horses between Episodes of Recurrent Exertional Rhabdomyolysis.

Certain Standardbred racehorses develop recurrent exertional rhabdomyolysis (RER-STD) for unknown reasons. We compared gluteal muscle histopathology and gene/protein expression between Standardbreds with a history of, but not currently experiencing rhabdomyolysis (N = 9), and race-trained controls (N = 7). Eight RER-STD had a few mature fibers with small internalized myonuclei, one out of nine had histologic evidence of regeneration and zero out of nine degeneration. However, RER-STD versus controls had 791/13,531 differentially expressed genes (DEG). The top three gene ontology (GO) enriched pathways for upregulated DEG (N = 433) were inflammation/immune response (62 GO terms), cell proliferation (31 GO terms), and hypoxia/oxidative stress (31 GO terms). Calcium ion regulation (39 GO terms), purine nucleotide metabolism (32 GO terms), and electron transport (29 GO terms) were the top three enriched GO pathways for down-regulated DEG (N = 305). DEG regulated RYR1 and sarcoplasmic reticulum calcium stores. Differentially expressed proteins (DEP ↑N = 50, ↓N = 12) involved the sarcomere (24% of DEP), electron transport (23%), metabolism (20%), inflammation (6%), cell/oxidative stress (7%), and other (17%). DEP included ↑superoxide dismutase, ↑catalase, and DEP/DEG included several cysteine-based antioxidants. In conclusion, gluteal muscle of RER-susceptible Standardbreds is characterized by perturbation of pathways for calcium regulation, cellular/oxidative stress, inflammation, and cellular regeneration weeks after an episode of rhabdomyolysis that could represent therapeutic targets.

Rhabdomyolysis, myoglobinuric nephrosis, and crystalline nephropathy in a captive bottlenose dolphin.

A 5-y-old female bottlenose dolphin (Tursiops truncatus) from an aquarium in Japan had clinical signs of anorexia, vomiting, and bradykinesia. Enrofloxacin and lactated Ringer solution were administered for treatment of bacterial infection and for rehydration. Elevations of creatine kinase and aspartate aminotransferase activities were detected on day 4 of treatment, indicating that rhabdomyolysis had developed on day 3. On day 5, serum creatinine and urea concentrations increased and remained high throughout the remaining treatment; the dolphin died on day 16. Postmortem examination revealed massive necrosis of the longissimus dorsi muscles. Histologic examination revealed extensive necrosis of skeletal myofibers, multifocal renal tubular necrosis with intratubular casts and crystals, and suppurative bronchopneumonia. The renal casts labeled positively with anti-myoglobin antibody; expression of aquaporin-1 was decreased in renal tubules compared to normal kidney tissue. To our knowledge, this description of clinicopathologic findings of rhabdomyolysis leading to acute kidney injury with concomitant crystalline nephropathy has not been reported previously in a bottlenose dolphin.

Hypoglycemia and presumptive rhabdomyolysis secondary to lisdexamfetamine toxicosis in 3 cats.

OBJECTIVE: To describe the clinical course and novel biochemical changes in 3 cats with lisdexamfetamine (LDX) toxicosis. SERIES SUMMARY: Three cats presented with LDX exposure and initially displayed typical clinical signs of amphetamine toxicosis. However, over the course of hospitalization, hypoglycemia and markedly elevated creatine kinase levels consistent with rhabdomyolysis ensued. All cats were treated with sedatives including phenothiazines and dexmedetomidine. Two cats were hospitalized for 4 days and 1 for 5 days. All cats survived. NEW OR UNIQUE INFORMATION PROVIDED: This is the first case series in cats that reports the novel biochemical changes of delayed hypoglycemia and elevated creatine kinase several days into hospitalization for the treatment of LDX toxicity. The development of delayed clinical signs suggests reconsideration of established hospitalization guidelines for amphetamine ingestion in cats.

Downer cow syndrome causing rhabdomyolysis and acute renal failure in a 17-month-old Guzerá heifer / Síndrome da vaca caída causando rabdomiólise e insuficiência renal aguda em uma novilha Guzerá de 17 meses

The downer cow syndrome (DCS) is characterized by an alert cow showing inability or reluctance to stand for 12 hours or more. This paper reported clinical, laboratory, and pathological findings in a Guzerá heifer with rhabdomyolysis, pigmenturia and acute renal failure following DCS. A 17-month-old Guzerá heifer was transported via a 350-km ride in a truck and showed sternal recumbency and severe difficulty in standing and walking. Neurological examination was unremarkable, and the heifer presented normal response to cranial nerves and spinal cord tests. Rectal palpation revealed a 5-month gravid uterus. No other abnormalities were noted in the pelvis or around the coxofemoral joints. Biochemical abnormalities included extremely high muscular enzyme activities (creatine phosphokinase and aspartate aminotransferase) and high creatinine levels. Urinalysis revealed blackish and cloudy urine, proteinuria, and a positive occult blood test. Spinal cord ultrasonography showed no abnormalities. This report highlighted an uncommon clinical presentation (myoglobinuria) and pathological findings in a heifer with DCS as a consequence of severe compressive muscle damage. Practitioners and producers must be aware of the risk of careless road transportation for long distances of cattle, especially obese cows, avoiding unnecessary suffering and expenses due to DCS.

A síndrome da vaca caída (SVC) é caracterizada por um bovino alerta que mostra incapacidade ou relutância em permanecer em estação por 12 horas ou mais. O objetivo deste trabalho é relatar os achados clínicos, laboratoriais e patológicos em uma novilha Guzerá com rabdomiólise, pigmentúria e insuficiência renal aguda após a SVC. Uma novilha da raça Guzerá, de 17 meses de idade, foi transportada de caminhão por 350 km e apresentou decúbito esternal, grande dificuldade para assumir estação e caminhar. O exame neurológico não demonstrou alterações, e a novilha possuía resposta normal aos testes de nervos cranianos e medula espinhal. A palpação retal revelou útero grávido de cinco meses. Nenhuma outra anormalidade foi observada na pelve ou na região das articulações coxofemorais. As anormalidades bioquímicas incluíram atividades de enzimas musculares (creatina fosfoquinase e aspartato aminotransferase) extremamente aumentadas e níveis elevados de creatinina. A urinálise revelou urina enegrecida e turva, proteinúria e teste de sangue oculto positivo. O exame ultrassonográfico da medula espinhal não apresentou anormalidades. Este relato evidencia uma apresentação clínica (mioglobinúria) e achados patológicos incomuns em uma novilha com SVC em consequência de extensa lesão muscular compressiva. Veterinários e produtores devem estar atentos aos riscos do transporte rodoviário descuidado por longas distâncias de bovinos, especialmente vacas obesas, evitando assim sofrimento e despesas desnecessárias decorrentes da SVC.

The role of selenium and vitamin E in a Transylvanian enzootic equine recurrent rhabdomyolysis syndrome.

A severe form of recurrent exertional rhabdomyolysis occurs enzootically in a well-defined region of Transylvania, Harghita county. At the highest lying two settlements (more than 800 m above sea level), the prevalence of equine rhabdomyolysis is between 17 and 23%, while in the neighbouring villages in the valley it is less than 2%. The objective of our study was to clarify the role of selenium and vitamin E in the high prevalence of rhabdomyolysis in that region. Soil and hay samples were collected from each area to evaluate mineral content. Ten horses from the non-affected and 20 horses from the affected area were tested for serum selenium, vitamin E, glutathione peroxidase (GSH-Px), muscle enzymes, lactate and electrolytes. Hay samples collected from the affected area had lower selenium content. Horses in the affected regions had significantly lower serum selenium (P = 0.006) and GSH-Px levels than animals living in the non-affected regions. A good correlation between erythrocyte GSH-Px and serum selenium concentration could be demonstrated (r = 0.777, P < 0.001). Serum vitamin E levels were low independently of the origin of the horse. Based on our results, selenium deficiency possibly has a role in the Transylvanian enzootic equine recurrent rhabdomyolysis syndrome.

Clothes dryer-induced heat stroke in three cats.

OBJECTIVE: To describe the clinical course of 3 cats successfully treated following clothes dryer-induced heat stroke. CASE SERIES SUMMARY: Three cats were treated after accidental clothes dryer-induced heat stroke. All cats fulfilled canine heat stroke criteria and showed evidence of heat injury, including neurological dysfunction, corneal and mucosal ulceration, and evidence of rhabdomyolysis. Coagulopathy, acute liver injury, acute kidney injury, cardiac dysfunction, and gastrointestinal signs were seen in cats with a longer duration of dryer exposure. NEW OR UNIQUE INFORMATION PROVIDED: Describes the management of cats after inadvertent clothes dryer-induced heat stroke.

Acute nontraumatic rhabdomyolysis in a Greyhound after albuterol toxicosis.

OBJECTIVE: To describe the clinical features of rhabdomyolysis due to albuterol toxicosis in a Greyhound. CASE SUMMARY: A 4-year-old neutered male Greyhound was presented for albuterol toxicosis leading to severe hypokalemia and respiratory paralysis. After 3 hours of mechanical ventilation, pigmenturia and marked enlargement, firmness, and pain of the left thigh muscles were noted. Severe hyperkalemia and cardiac arrhythmias were identified after turning the patient. After discontinuation of mechanical ventilation, other muscles became involved, and the patient developed acute kidney injury and concern for multiple organ dysfunction syndrome over the next 5 days. On day 6, the patient was euthanized, and necropsy revealed myocardial and skeletal muscle necrosis, myoglobinuria, and acute tubular degeneration. NEW OR UNIQUE INFORMATION PROVIDED: To the authors' knowledge, this is the first case of albuterol toxicosis leading to rhabdomyolysis.

Successful Treatment of Capture Myopathy and Satellite Transmitter Injury in an Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos).

An Atlantic yellow-nosed albatross (Thalassarche chlororhynchos) was found on shore 3 days after having been captured at sea by researchers. It presented very lethargic, moderately dehydrated, and in poor body condition. It was mildly hypothermic, with moderate pediculosis, and dark malodorous feces with yellow urates. The bird had a 48-g satellite transmitter attached with a backpack-style chest harness, which caused an ulcerative lesion on the interscapular area. The bird was severely anemic (packed cell volume, 18%), and plasma chemistry results were suggestive of a severe rhabdomyolysis (aspartate transaminase, 3620 U/L; creatine kinase, 100 400 U/L). We hypothesized that capture myopathy occurred because of a combination of capture stress and prolonged physical restraint by researchers, stress associated with repeated attempts by the bird to remove the satellite-transmitter harness, and a lengthy road transport to the rehabilitation center. A treatment protocol, which relied on a combination of aggressive fluid therapy, selenium, vitamins E and B12, and multivitamin supplementation, was administered after the initial physical assessment of the albatross. Isoflurane inhalation anesthesia was used to minimize stress associated with the performed medical procedures (eg, physical examination, removal of the satellite transmitter harness, blood collection, and wound management). Measures were adopted while the bird was hospitalized to reduce stress (eg, quiet and comfortable environment with visual barriers and restricting handling of the patient to experienced staff). Clinical and hematological monitoring was used to assess the patient's condition as the bird gradually recovered while hospitalized. The albatross was successfully released 28 days after the initial presentation, suggesting that the medical protocol employed in this case may be useful for the treatment of capture myopathy in albatrosses and other birds.

MYH1 is a candidate gene for recurrent rhabdomyolysis in humans.

Rhabdomyolysis is a serious medical condition characterized by muscle injury, and there are recognized genetic causes especially in recurrent forms. The majority of these cases, however, remain unexplained. Here, we describe a patient with recurrent rhabdomyolysis in whom extensive clinical testing failed to identify a likely etiology. Whole-exome sequencing revealed a novel missense variant in MYH1, which encodes a major adult muscle fiber protein. Structural biology analysis revealed that the mutated residue is extremely well conserved and is located in the actin binding cleft. Furthermore, immediately adjacent mutations in that cleft in other myosins are pathogenic in humans. Our results are consistent with the finding that MYH1 is mutated in rhabdomyolysis in horses and suggest that this gene should be investigated in cases with recurrent rhabdomyolysis.

Correlation Between Serum Activity of Muscle Enzymes and Stage of the Estrous Cycle in Italian Standardbred Horses Susceptible to Exertional Rhabdomyolysis.

Equine exertional rhabdomyolysis (ER) is a well-recognized clinical syndrome affecting racehorses. Prevalence analysis of ER showed that female sex was a significant risk factor. The aim of this research was to evaluate the differences and correlations in the serum activity of muscle enzymes and the stage of the estrous cycle in ER-susceptible and control (C) mares. Serum muscle enzyme activity before and after exercise and sex hormones were analyzed in the two groups of mares. Ten cyclic ER and 10 cyclic C mares were examined weekly for 4 weeks. During diestrus, ER horses had significantly higher resting and postexercise aspartate aminotransferase (AST) activity, but not creatine kinase (CK) activity, compared with controls; only postexercise AST activity was significantly higher during estrus compared with activity levels in controls. During estrus, 17ß-estradiol and AST activity were significantly negatively correlated in the control but not ER mares. Based on our results, further studies should be performed to characterize the presumptive different roles played by sexual hormones in horses susceptible to ER compared with healthy mares.

Capture-induced exertional rhabdomyolysis in the Shortfin Mako Shark, Isurus oxyrinchus.

BACKGROUND: Shortfin Mako sharks (Isurus oxyrinchus) are top-order predators in oceanic food chains. They are captured worldwide by commercial and recreational fisheries, but little is known about the effects that fishing has on the homeostasis and longevity of these animals. OBJECTIVE: This study aimed to assess the health of Shortfin Mako sharks captured by recreational fishers off eastern Australia. METHODS: Twenty-four sharks were captured, and their gender, length, weight, reproductive maturity, and stage were recorded. After blood and urine collection, serum analytes were quantified using standard biochemical methods, whereas urine was analyzed using semi-quantitative reagent strips, microscopic examination, centrifugation, and ammonium sulfate precipitation tests. RESULTS: Six Makos presented with red-brown urine. The means of notable serum analytes were as follows: sodium 276 mmol/L, potassium 15.6 mmol/L, inorganic phosphate 10.6 mmol/L, magnesium 3.3 mmol/L, urea 325 mmol/L, creatinine 52 µmol/L, AST 2806 U/L, CK 240938 U/L, lactate 44.4 mmol/L, osmolarity 1160 mmol/L, and pH 7.13. These analytes differed from the respective sand tiger shark reference interval, which was used as a proxy for Makos. The red-brown urine was due to myoglobin and had a mean pH of 5.76 that, when combined with red-brown casts, led to a diagnosis of fishing-induced exertional rhabdomyolysis that occurred secondary to lactic acidosis, hypoxia, and hypovolemia. It was further exacerbated by hyperkalemia and acute renal failure, serious complications that often lead to mortality. CONCLUSIONS: Practitioners caring for sharks and rays should consider collecting urine from free-living or aquarium animals when they are captured for examination and/or treatment, particularly at times with maximal seawater temperatures.

Compartment syndrome of the muscles of mastication in a working dog following a traumatic training incident.

OBJECTIVE: To describe acute compartment syndrome (CS) of the muscles of mastication in a working dog associated with a traumatic training event. CASE SUMMARY: A 2.5-year-old male Belgian Malinois was evaluated for acute blindness, severe diffuse swelling of the head, and inability to close the jaw following a traumatic incident during a bite training drill. During the exercise, the maxillary canine teeth were locked on a bite sleeve. Magnetic resonance imaging of the head and ocular system identified diffuse muscle swelling and hyperintensity, most severe in the muscles of mastication. Ocular abnormalities were not identified. Rhabdomyolysis, CS, and indirect optic nerve injury were supported by measurement of increased intramuscular pressure. Bilateral decompressive fasciotomies over the masseter and temporalis muscles resulted in immediate and marked resolution of the swelling and jaw movement. Blindness, however, did not resolve. NEW OR UNIQUE INFORMATION PROVIDED: CS involving the muscles of mastication may occur as a complication of bite training and may result in irreversible and even life-threatening complications. Emergent decompressive fasciotomy is indicated to reverse swelling; however, visual deficits may not resolve.

Coding sequences of sarcoplasmic reticulum calcium ATPase regulatory peptides and expression of calcium regulatory genes in recurrent exertional rhabdomyolysis.

BACKGROUND: Sarcolipin (SLN), myoregulin (MRLN), and dwarf open reading frame (DWORF) are transmembrane regulators of the sarcoplasmic reticulum calcium transporting ATPase (SERCA) that we hypothesized played a role in recurrent exertional rhabdomyolysis (RER). OBJECTIVES: Compare coding sequences of SLN, MRLN, DWORF across species and between RER and control horses. Compare expression of muscle Ca2+ regulatory genes between RER and control horses. ANIMALS: Twenty Thoroughbreds (TB), 5 Standardbreds (STD), 6 Quarter Horses (QH) with RER and 39 breed-matched controls. METHODS: Sanger sequencing of SERCA regulatory genes with comparison of amino acid (AA) sequences among control, RER horses, human, mouse, and rabbit reference genomes. In RER and control gluteal muscle, quantitative real-time polymerase chain reaction of SERCA regulatory peptides, the calcium release channel (RYR1), and its accessory proteins calsequestrin (CASQ1), and calstabin (FKBP1A). RESULTS: The SLN gene was the highest expressed horse SERCA regulatory gene with a uniquely truncated AA sequence (29 versus 31) versus other species. Coding sequences of SLN, MRLN, and DWORF were identical in RER and control horses. A sex-by-phenotype effect occurred with lower CASQ1 expression in RER males versus control males (P < .001) and RER females (P = .05) and higher FKBP1A (P = .01) expression in RER males versus control males. CONCLUSIONS AND CLINICAL IMPORTANCE: The SLN gene encodes a uniquely truncated peptide in the horse versus other species. Variants in the coding sequence of SLN, MLRN, or DWORF were not associated with RER. Males with RER have differential gene expression that could reflect adaptations to stabilize RYR1.

Prevalence of the E321G MYH1 variant for immune-mediated myositis and nonexertional rhabdomyolysis in performance subgroups of American Quarter Horses.

BACKGROUND: Immune-mediated myositis (IMM) in American Quarter Horses (QHs) causes acute muscle atrophy and lymphocytic infiltration of myofibers. Recently, an E321G mutation in a highly conserved region of the myosin heavy chain 1 (MYH1) gene was associated with susceptibility to IMM and nonexertional rhabdomyolysis. OBJECTIVES: To estimate prevalence of the E321G MYH1 variant in the QH breed and performance subgroups. ANIMALS: Three-hundred seven elite performance QHs and 146 random registered QH controls. METHODS: Prospective genetic survey. Elite QHs from barrel racing, cutting, halter, racing, reining, Western Pleasure, and working cow disciplines and randomly selected registered QHs were genotyped for the E321G MYH1 variant and allele frequencies were calculated. RESULTS: The E321G MYH1 variant allele frequency was 0.034 ± 0.011 in the general QH population (6.8% of individuals in the breed) and the highest among the reining (0.135 ± 0.040; 24.3% of reiners), working cow (0.085 ± 0.031), and halter (0.080 ± 0.027) performance subgroups. The E321G MYH1 variant was present in cutting (0.044 ± 0.022) and Western Pleasure (0.021 ± 0.015) QHs at lower frequency and was not observed in barrel racing or racing QHs. CONCLUSIONS AND CLINICAL IMPORTANCE: Knowing that reining and working cow QHs have the highest prevalence of the E321G MYH1 variant and that the variant is more prevalent than the alleles for hereditary equine regional dermal asthenia and hyperkalemic periodic paralysis in the general QH population will guide the use of genetic testing for diagnostic and breeding purposes.

Acute kidney injury secondary to traumatic rhabdomyolysis in a dog.

OBJECTIVE: To describe the clinical course and successful management of a dog with crush syndrome, rhabdomyolysis, myoglobinuria, and associated acute kidney injury (AKI). CASE SUMMARY: An 8-year-old female, neutered, mixed-breed dog was referred to the Veterinary Teaching Hospital due to crush injury and suspected AKI. Blood tests and urinalysis showed markedly increased serum creatine kinase activity, myoglobinuria, and AKI. The dog was managed successfully with intermittent hemodialysis, and completely recovered. NEW OR UNIQUE INFORMATION PROVIDED: This is the first report of a dog with crush syndrome with secondary myoglobinuria and AKI.