Harrison intenal medicine

Disorders of Adhesion Two main types of leukocyte adhesion deficiency (LAD) have been described, LAD 1 and LAD 2. Both are autosomal recessive traits and result in the inability of neutrophils to exit the circulation to sites of infection, leading to leukocytosis and increased susceptibility to infection (Fig. 61-8). Patients with LAD 1 have mutations in CD18, the common component of the integrins LFA-1, Mac-1, and p150,95, leading to a defect in tight adhesion between neutrophils and the endothelium.

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Miscellaneous Metabolic disorders—ketoacidosis, acute renal failure, eclampsia, acute poisoning Drugs—lithium Other—metastatic carcinoma, acute hemorrhage or hemolysis Abnormal Neutrophil Function Inherited and acquired abnormalities of phagocyte function are listed in Table 61-3. The resulting diseases are best considered in terms of the functional defects of adherence, chemotaxis, and microbicidal activity. The distinguishing features of the important inherited disorders of phagocyte function are shown in Table 61-4.

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Tham khảo tài liệu 'chapter 061. disorders of granulocytes and monocytes (part 6)', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả

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Neutrophil Abnormalities A defect in the neutrophil life cycle can lead to dysfunction and compromised host defenses. Inflammation is often depressed, and the clinical result is often recurrent with severe bacterial and fungal infections. Aphthous ulcers of mucous membranes (gray ulcers without pus) and gingivitis and periodontal disease suggest a phagocytic cell disorder. Patients with congenital phagocyte defects can have infections within the first few days of life. Skin, ear, upper and lower respiratory tract, and bone infections are common. Sepsis and meningitis are rare.

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Neutrophil travel through the pulmonary capillaries is dependent on neutrophil deformability. Neutrophil rigidity (e.g., caused by C5a) enhances pulmonary trapping and response to pulmonary pathogens in a way that is not so dependent on cell-surface receptors. Intraalveolar chemotactic factors, such as those caused by certain bacteria (e.g., Streptococcus pneumoniae) lead to diapedesis of neutrophils from the pulmonary capillaries into the alveolar space. Neutrophil interaction with the endothelium of the systemic postcapillary venules is dependent on molecules of attachment.

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Pelger-Hüet anomaly. In this benign disorder, the majority of granulocytes are bilobed. The nucleus frequently has a spectacle-like, or "pince-nez," configuration. In severe acute bacterial infection, prominent neutrophil cytoplasmic granules, called toxic granulations, are occasionally seen. Toxic granulations are immature or abnormally staining azurophil granules. Cytoplasmic inclusions, also called Döhle bodies (Fig. 61-3), can be seen during infection and are fragments of ribosome-rich endoplasmic reticulum.

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Stages of neutrophil development shown schematically. G-CSF (granulocyte colony-stimulating factor) and GM-CSF (granulocytemacrophage colony-stimulating factor) are critical to this process. Identifying cellular characteristics and specific cell-surface markers are listed for each maturational stage. Figure 61-3 Neutrophil band with Döhle body. The neutrophil with a sausage-shaped nucleus in the center of the field is a band form.

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Harrison's Internal Medicine Chapter 61. Disorders of Granulocytes and Monocytes Disorders of Granulocytes and Monocytes: Introduction Leukocytes, the major cells comprising inflammatory and immune responses, include neutrophils, T and B lymphocytes, natural killer (NK) cells, monocytes, eosinophils, and basophils. These cells have specific functions, such as antibody production by B lymphocytes or destruction of bacteria by neutrophils, but in no single infectious disease is the exact role of the cell types completely established.

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The absence of the spleen has minimal long-term effects on the hematologic profile. In the immediate postsplenectomy period, leukocytosis (up to 25,000/µL) and thrombocytosis (up to 1 x 106/µL) may develop, but within 2–3 weeks, blood cell counts and survival of each cell lineage are usually normal.

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Differential Diagnosis Many of the diseases associated with splenomegaly are listed in Table 60-2. They are grouped according to the presumed basic mechanisms responsible for organ enlargement: 1.

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The differential diagnostic possibilities are much fewer when the spleen is "massively enlarged," palpable more than 8 cm below the left costal margin or its drained weight is ≥1000 g (Table 60-3). The vast majority of such patients will have non-Hodgkin's lymphoma, chronic lymphocytic leukemia, hairy cell leukemia, chronic myelogenous leukemia, myelofibrosis with myeloid metaplasia, or polycythemia vera.

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Approach to the Patient: Splenomegaly Clinical Assessment The most common symptoms produced by diseases involving the spleen are pain and a heavy sensation in the LUQ. Massive splenomegaly may cause early satiety. Pain may result from acute swelling of the spleen with stretching of the capsule, infarction, or inflammation of the capsule. For many years it was believed that splenic infarction was clinically silent, which at times is true.

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Splenomegaly Structure and Function of the Spleen The spleen is a reticuloendothelial organ that has its embryologic origin in the dorsal mesogastrium at about 5 weeks' gestation. It arises in a series of hillocks, migrates to its normal adult location in the left upper quadrant (LUQ), and is attached to the stomach via the gastrolienal ligament and to the kidney via the lienorenal ligament. When the hillocks fail to unify into a single tissue mass, accessory spleens may develop in around 20% of persons. The function of the spleen has been elusive.

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Laboratory Investigation The laboratory investigation of patients with lymphadenopathy must be tailored to elucidate the etiology suspected from the patient's history and physical findings. One study from a family practice clinic evaluated 249 younger patients with "enlarged lymph nodes, not infected" or "lymphadenitis." No laboratory studies were obtained in 51%. When studies were performed, the most common were a complete blood count (CBC) (33%), throat culture (16%), chest x-ray (12%), or monospot test (10%).

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Mixing Studies Mixing studies are used to evaluate a prolonged aPTT or, less commonly PT, to distinguish between a factor deficiency and an inhibitor. In this assay, normal plasma and patient plasma are mixed in a 50:50 ratio, and the aPTT or PT is determined immediately and after incubation at 37oC for varying times, typically 30, 60, and/or 120 min. With isolated factor deficiencies, the aPTT will correct with mixing and stay corrected with incubation. With aPTT prolongation due to a lupus anticoagulant, the mixing and incubation will show no correction.

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Harrison's Internal Medicine Chapter 60. Enlargement of Lymph Nodes and Spleen Enlargement of Lymph Nodes and Spleen: Introduction This chapter is intended to serve as a guide to the evaluation of patients who present with enlargement of the lymph nodes (lymphadenopathy) or the spleen (splenomegaly). Lymphadenopathy is a rather common clinical finding in primary care settings, whereas palpable splenomegaly is less so.

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Screening Assays The most commonly used screening tests are the PT, aPTT, and platelet count. The PT assesses the factors I (fibrinogen), II (prothrombin), V, VII and X (Fig. 59-6). The PT measures the time for clot formation of the citrated plasma after recalcification and addition of thromboplastin, a mixture of TF and phospholipids. The sensitivity of the assay varies by the source of thromboplastin.

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The most important point in a history related to venous thrombosis is whether the thrombotic event was idiopathic (meaning there was no clear precipitating factor) or was a precipitated event. In patients without underlying malignancy, having an idiopathic event is the strongest predictor of recurrence of venous thromboembolism. In patients who have a vague history of thrombosis, a history of being treated with warfarin suggests a past DVT.

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Underlying Systemic Diseases that Cause or Exacerbate a Bleeding Tendency Acquired bleeding disorders are commonly secondary to, or associated with, systemic disease. The clinical evaluation of a patient with a bleeding tendency must therefore include a thorough assessment for evidence of underlying disease. Bruising or mucosal bleeding may be the presenting complaint in liver disease, severe renal impairment, hypothyroidism, paraproteinemias or amyloidosis, and conditions causing bone marrow failure.

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Vitamin D Photochemistry Cutaneous exposure to UV-B causes photolysis of epidermal 7dehydrocholesterol converting it to pre-vitamin D3, which then undergoes a temperature-dependent isomerization to form the stable hormone vitamin D3. This compound then diffuses to the dermal vasculature and circulates systemically where it is converted to the functional hormone 1,25-dihydroxyvitamin D3[1,25(OH)2D3]. Vitamin D metabolites from the circulation or those produced in the skin itself can augment epidermal differentiation signaling.

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