Biomedical subjects
Publications and source records attributed to Lillian McMahon.
Sickle cell disease (SCD) may have ocular complications. We present the a case of a patient with SCD, with an acute painful episode involving the limbs and periorbital region, who also twice developed an unusual complication of recurrent bilateral lacrimal gland enlargement, not previously reported in the medical literature.
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Inflammation may play an important role in the pathophysiology of sickle cell disease (SCD), and recent studies have identified the 70-kDa heat shock protein (Hsp70) as an important mediator of inflammatory responses. Here we demonstrate a significant increase in circulating serum Hsp70 level in SCD during vaso-occlusive crisis (VOC) as compared with baseline steady-state levels (P <0.05) and a significant increase in Hsp70 levels in SCD at baseline compared with normal controls (P <0.05). Taken together, these results indicate that circulating serum Hsp70 might be a marker for VOC in SCD.
Sickle hemoglobin (Hb S; beta Glu6Val) is due to an A GTG; beta Lys132Asn, AAA>AAC). When present alone, the beta Lys132Asn mutation has low oxygen affinity. Therefore, this mutation may enhance the polymerization of the Hb S variant. Furthermore, the variant hemoglobin mimics Hb A on high-pressure liquid chromatography, and its identity is not easily diagnosed. A succinct review of variant sickle hemoglobins is also presented.
The purpose of the study was to examine endothelium-dependent and -independent vasodilation of conduit and resistance vessels in sickle cell anemia (HbSS). We measured the effects of intra-arterial infusion of methacholine, sodium nitroprusside, and NG-monomethyl-L-arginine (L-NMMA) on forearm blood flow using venous occlusion plethysmography in eight patients with HbSS and 11 HbAA controls. We assessed vasodilation of the conduit brachial artery using ultrasound in 17 patients with HbSS and 41 nonanemic controls. Forearm blood flow response to methacholine was similar in HbSS and HbAA, while the response to sodium nitroprusside was greater in those with HbSS. Nitric oxide synthase inhibition with L-NMMA attenuated methacholine-induced forearm blood flow to a lesser extent in HbSS compared to HbAA, suggesting diminished nitric oxide (NO) contribution to endothelium-dependent vasodilation. Flow-mediated and nitroglycerin-induced dilation were impaired in HbSS compared to controls and were not affected by the antioxidant vitamin C or the precursor substrate for NO synthesis L-arginine. NO bioactivity is reduced but differs in peripheral conduit and resistance vessels in HbSS. Resistance vessels have preserved response to exogenous NO donors but have diminished contribution of NO to endothelium-dependent vasodilation. Conduit vessels demonstrate impaired vasodilation to endogenous and exogenous NO.
BACKGROUND: Acute chest syndrome (ACS) is the leading cause of hospitalization, morbidity, and mortality in patients with sickle cell disease. Radiographic and clinical findings in ACS resemble pneumonia; however, etiologies other than infectious pathogens have been implicated, including pulmonary fat embolism (PFE) and infarction of segments of the pulmonary vasculature. The National Acute Chest Syndrome Study Group was designed to identify the etiologic agents and clinical outcomes associated with this syndrome. METHODS: Data were analyzed from the prospective study of 671 episodes of ACS in 538 patients with sickle cell anemia. ACS was defined as a new pulmonary infiltrate involving at least 1 complete segment of the lung, excluding atelectasis. In addition, the patients had to have chest pain, fever >38.5C, tachypnea, wheezing, or cough. Samples of blood and deep sputum were analyzed for evidence of bacteria, viruses, and PFE. Mycoplasma pneumoniae infection was determined by analysis of paired serologies. Detailed information on patient characteristics, presenting signs and symptoms, treatment, and clinical outcome were collected. RESULTS: Fifty-one (9%) of 598 episodes of ACS had serologic evidence of M pneumoniae infection. Twelve percent of the 112 episodes of ACS occurring in patients younger than 5 years were associated with M pneumoniae infection. At the time of diagnosis, 98% of all patients with M pneumoniae infection had fever, 78% had a cough, and 51% were tachypneic. More than 50% developed multilobar infiltrates and effusions, 82% were transfused, and 6% required assisted ventilation. The average hospital stay was 10 days. Evidence of PFE with M pneumoniae infection was seen in 5 (20%) of 25 patients with adequate deep respiratory samples for the PFE assay. M pneumoniae and Chlamydia pneumoniae was found in 16% of patients with diagnostic studies for C pneumoniae. Mycoplasma hominis was cultured in 10 (2%) of 555 episodes of ACS and occurred more frequently in older patients, but the presenting symptoms and clinical course was similar to those with M pneumoniae. CONCLUSIONS: M pneumoniae is commonly associated with the ACS in patients with sickle cell anemia and occurs in very young children. M hominis should be considered in the differential diagnosis of ACS. Aggressive treatment with broad-spectrum antibiotics, including 1 from the macrolide class, is recommended for all patients as well as bronchodilator therapy, early transfusion, and respiratory support when clinically indicated.