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General Thermography
Published in James Stewart Campbell, M. Nathaniel Mead, Human Medical Thermography, 2023
James Stewart Campbell, M. Nathaniel Mead
The thymus gland is located in the anterior chest, in front of the upper portion of the heart and trachea (Figure 10.61). It is proportionally large in infancy but shrinks with age. At puberty, it weighs 30 to 50 grams, and by old age, it typically weighs 5 to 15 grams. The thymus rarely becomes neoplastic, developing into a lymphoma or thymoma. Lymphomas occupying superficial lymph nodes may appear warm on thermographic analysis, but this warmth is not associated with the thymus gland itself.165 Thymomas, on the other hand, may become large enough to become detectable as a warm area in the upper anterior chest, but no studies confirming this have been published. Though some thermographers claim that cool areas over the anterior or posterior upper chest are a sign of “underactive thymus,” this is doubtful because of the small size and normally low metabolic activity of the gland in adulthood. A cool area over the upper sternum may instead be due to the presence of thymic cysts, which may become as large as 4 cm (1.6 in.) in diameter. No studies are available concerning cool areas over the thymus gland. MRI and CAT scans can determine anatomic thymus abnormalities, while hematology can monitor the physiologic and pathologic activity of the gland.166
The Thoracic Lymphatic System and Lymph Nodes, and the Spread of Tumours within the Lungs, the Tracheobronchial Tree and the Mediastinum.
Published in Fred W Wright, Radiology of the Chest and Related Conditions, 2022
Lymphocytes are the basic cells of the lymphoid system and are of three main types - B, T and Null (i.e. not B or T). B lymphocytes when stimulated by antigens differentiate into plasma-cells which in turn produce antibodies. T lymphocytes are of several types: - (i) T-helper cells which produce cytokines and assist B lymphocytes, macrophages and granulocytes, (ii) T-cytoxic cells which destroy cells infected with viruses and tumour cells, and (iii) T-suppressor cells which turn down an immune response. Null cells destroy cells coated with antibodies. T cells are particularly produced in the thymus. Lymphocytes circulate in the blood, rapidly detect antigens (many are specific to certain antigens) and stimulate the production of more lymphocytes in nodes etc. to cause the immune response.
Thymectomy
Published in Mark Davenport, James D. Geiger, Nigel J. Hall, Steven S. Rothenberg, Operative Pediatric Surgery, 2020
It is well known that the thymus is necessary for the development of cellular immunity and T lymphocytes. However, once past infancy the thymus seems to have little function and removal causes no alterations in immune function of normal individuals. The role of the thymus in MG is now clearly recognized and thymectomy is an established and accepted therapy as part of the overall treatment plan. Myasthenia is an autoimmune disorder of the postsynaptic nicotinic acetylcholine receptor and manifests as weakness and fatigue of skeletal muscles. Ptosis, diplopia, dystonia, and loss of facial expression are often common early findings. More severe symptoms include severe weakness and even respiratory compromise. Initial medical therapy consists of drugs aimed at blocking the effect of antibodies at the neuromuscular junction. First-line drugs are anticholinesterases, such as pyridostigmine and mestinon. Steroids and other immunosuppressants are used in more severe cases. Plasmapheresis has also been used to filter out antibodies to the acetylcholine receptors.
Lung, Liver and Skin Changes in an Infant with Positive Methamphetamine
Published in Fetal and Pediatric Pathology, 2023
Kunasilan Subramaniam, Hilma bt. Hazmi, Yong Swee Guan, Khairul Anuar bin Zainun
Post mortem examination showed an extensive erythematosus rash involving his lips, left ear, around his neck, extensor surface of his upper limbs and lower limbs, both antecubital fossa, bilateral axillae, inguinal, perineal, gluteal and lower back regions (Fig. 1). He was pale and dehydrated, but there were no visible injuries on his body. He was small for his age. His crown heel length was 61 cm (-3SD), his head circumference was 38 cm (<3rd centile), and he weighed 4650 g (<3SD). On the internal examination, the skin showed translucency due to loss of subcutaneous tissues. The chest cavities contained minimal serous fluid. His right lung weighed 41 g and left lung weighed 33 g (normal weight for lungs combined: 99.7–176 grams). The thymus has involuted. The liver was fatty (Fig. 2). Histologically, the lungs showed fibrinoid necrosis of arterial walls (Fig. 3), and pulmonary congestion, but no hemorrhage. No fibroid necrosis was apparent in other organs. The liver showed predominantly diffuse macrovesicular fatty changes (Fig. 4). Brain sections showed no edema or encephalitis. The histology section of the skin taken from the erythematosus area showed epidermal pallor, parakeratosis, and keratinocyte necrolysis. There was no inflammatory cells infiltration in the epidermis or dermis.
Heterogeneity in myasthenia gravis: considerations for disease management
Published in Expert Review of Clinical Immunology, 2021
Amelia Evoli, Gregorio Spagni, Gabriele Monte, Valentina Damato
Inflammatory and neoplastic alterations of the thymus are involved in the disease pathogenesis in a high proportion of patients. Early-onset AChR-MG is typically associated with thymus follicular hyperplasia (TFH), characterized by expansion of the thymic perivascular space by peripheral T and B cell infiltration and lymphoid follicles. Both in MG and in normal thymus, myoid cells express the muscle AChR (mostly the fetal isoform) and thymic epithelial cells (TECs) express single AChR subunits [24,25]. An inflammatory environment in the thymus can favor an imbalance between activated T cells and Treg cells, associated with B lymphocyte recruitment and subsequent formation of ectopic germinal centers ultimately leading to AChR Ab production by mature B cells [25,26]. Autoreactive T and B cells migrate to the periphery and the disease-specific Ab response goes on, fostered by dysfunctional immunoregulation and release of AChRs from the damaged muscle membranes.
An update on thymectomy in myasthenia gravis
Published in Expert Review of Neurotherapeutics, 2019
In this scenario, the role of thymectomy differs in patients with neoplastic and non-neoplastic thymus. In the presence of a thymoma, surgery is aimed at removing a tumor and is indicated whenever feasible, irrespective of weakness extension and MG subtype. In patients with a non-neoplastic thymus, thymectomy is performed to improve MG (therapeutic thymectomy). It is mostly performed in patients with generalized disease and, given the current evidence for thymus role in MG pathogenesis, in those with AChR-MG [44–46]. Therapeutic thymectomy is by no means an alternative to immunosuppression. In patients with moderate to severe symptoms, surgery should be postponed until optimal MG control is achieved through medical treatment, in association with plasma-exchange or IVIg, when necessary.