Atherosclerosis is an inflammatory process that involves activation of matrix metalloproteinases (MMPs); MMPs degrade collagen and allow for smooth-muscle cell migration within a vessel. Moreover, this begets an accumulation of other cellular material, resulting in occlusion of the vessel and ischemic events to tissues in need of nutrients. Homocysteine has been shown to activate MMPs via an increase in oxidative stress and acting as a signaling molecule on receptors like the peroxisome proliferator activated receptor-γ and N-methyl-D-aspartate receptor. Nitric oxide has been shown to be beneficial in some cases of deactivating MMPs. However, in other cases, it has been shown to be harmful. Further studies are warranted on the scenarios that are beneficial versus destructive. Hydrogen sulfide (H2S) has been shown to decrease MMP activities in all cases in the literature by acting as an antioxidant and vasodilator. Various MMP-knockout and gene-silencing models have been used to determine the function of the many different MMPs. This has allowed us to discern the role that each MMP has in promoting or alleviating pathological conditions. Furthermore, there has been some study into the MMP polymorphisms that exist in the population. The purpose of this review is to examine the role of MMPs and their polymorphisms on the development of atherosclerosis, with emphasis placed on pathways that involve nitric oxide, hydrogen sulfide, and homocysteine.

Clostridium difficile (C diff) colitis infection is the most common cause of nosocomial infectious diarrhea and the prevalence is increasing worldwide. Toxic megacolon is a severe complication of C diff colitis associated with high mortality. Gastrointestinal (GI) comorbidity and impaired smooth muscle contraction are risk factors for the development of C diff-associated toxic megacolon. We present a case of fulminant C diff colitis with toxic megacolon in a patient with Duchenne muscular dystrophy (DMD) in the intensive care unit. C diff colitis was diagnosed by clinical presentation and positive C diff DNA amplification test (polymerase chain reaction). The impairment of GI tract due to DMD predisposes these patients to severe C diff infection and toxic megacolon, as observed in this case report. For the same reason, the recovery of GI function in these patients can be prolonged. While surgery was conducted for relieving the pressure from toxic megacolon, fecal microbiota transplantation through colonoscopy resulted in successful resolution of the C diff symptoms, although the recovery is prolonged due to DMD.

Gastrointestinal (GI) complication used to be the second most common complication in renal transplant patients after infection (Bardaxoglou et al. in Transpl Int 6(3):148-152, 1993). Review of transplant registry reveals that GI complication is no longer the second most common type of complication after renal transplant, but that it is still a common cause of significant amount of deaths in renal transplant recipients (De Bartolomeis et al. in Transpl Proc 37(6):2504-2506, 2005). In a study of 1,515 adults with severe GI complication after renal transplant, Sarkio et al. (Transpl Int 17(9):505-510, 2004) reported that gastroduodenal ulcers followed by colon perforation were the two biggest groups of GI complications during the first year after renal transplantation. Colonic perforation is estimated to occur in about 1 % of all cases of renal transplant patients, and it does predispose to potentially fatal complication. About 50 % of all colonic perforation is due to complication of acute inflammation of diverticular disease (Bardaxoglou et al. in Transpl Int 6(3):148-152, 1993; Guice et al. in Am J Surg 138(1):43-48, 1979; Koneru et al. in Arch Surg 125(5):610-613, 1990; Coccolini et al. in Transpl Proc 41(4):1189-1190, 2009). This is particularly so because these patients were previously exposed to uremia before transplantation which alters their protein metabolism hence interfering with tissue healing there after (Carson et al. in Ann Surg 188(1):109-113, 1978). GI complications including colon perforation after renal transplantation have effect on a patient's long-term survival (Gil-Vernet et al. in Transpl Proc 39(7):2190-2193, 2007). Despite this, the role of renal transplantation medication compared to anatomic anomaly in GI complication has been equivocal.

Chest pain requires a detailed differential diagnosis with good history-taking skills to differentiate between cardiogenic and noncardiogenic causes. Moreover, when other symptoms such as fever and elevated white blood cell count are involved, it may be necessary to consider causes that include infectious sources. A 53-year-old female with no significant past medical history returned to the hospital with recurrent complaints of chest pain that was constant, substernal, reproducible, and exacerbated with inspiration and expiration. The chest pain was thought to be noncardiogenic, as electrocardiography did not demonstrate changes, and cardiac enzymes were found to be negative for signs of ischemia. The patient’s blood cultures were analyzed from a previous admission and were shown to be positive for Staphylococcus aureus. The patient was started empirically on vancomycin, which was later switched to ceftriaxone as the bacteria were more sensitive to this antibiotic. A transthoracic echocardiogram did not demonstrate any vegetation or signs of endocarditis. There was a small right pleural effusion discovered on X-ray. Therefore, computed tomography as well as magnetic resonance imaging of the chest were performed, and showed osteomyelitis of the chest. The patient was continued on intravenous ceftriaxone for a total of 6 weeks. Tests for HIV, hepatitis A, B, and C were all found to be negative. The patient had no history of childhood illness, recurrent infections, or previous trauma to the chest, and had had no recent respiratory infections, pneumonia, or any underlying lung condition. Hence, her condition was thought to be a case of primary sternal osteomyelitis without known cause.

Myocardial infarction (MI) due to coronary atherosclerosis in young adults is uncommon; rare causes such as cocaine abuse, arterial dissection, and thromboembolism should be considered. A 21-year-old football player, and otherwise healthy African American man, developed chest pain during exercise while bench-pressing 400 lbs. Acute MI was diagnosed based on physical examination, electrocardiography findings, and elevated cardiac enzymes. Coronary arteriography showed a thrombus occluding the proximal left anterior descending artery (LAD). Aggressive antiplatelet therapy with aspirin, clopidogrel, and eptifibatide was pursued, in addition to standard post-MI care. This led to the successful resolution of symptoms and dissolution of the thrombus, demonstrated by repeat coronary arteriography. Five months later, he presented with similar symptoms during exercise after lifting heavy weights, and was found to have another acute MI. Coronary arteriography again showed a thrombus occluding the LAD. No evidence of coronary artery dissection or vasospasm was found. Only mild atherosclerotic plaque burden was observed on both occasions by intravascular ultrasound. A bare metal stent was placed at the site as it was thought this site had acted as a nidus for small plaque rupture and thrombus formation. Elevated serum factor VIII activity at 205% (reference range 60%–140%) was found, a rare cause of hypercoagulability. Further workup revealed a patent foramen ovale during a Valsalva maneuver by transesophageal echocardiography. Both events occurred during weight lifting, which can transiently increase right heart pressure in a similar way to the Valsalva maneuver. In light of all the findings, we concluded that an exercise-related increase in factor VIII activity led to coronary arterial thrombosis in the presence of a small ruptured plaque. Alternatively, venous clots may have traversed the patent foramen ovale and occluded the LAD. In addition to continuing aggressive risk factor modification, anticoagulation therapy with warfarin was initiated with close follow-up.