A 45-year old patient presented with fever, night sweats and weight loss. On X-ray, a mass was seen in apical lobe. On histopathology, caseous necrosis was present. What is the name of underlying process?
Ans. d. Hypersensitivity reaction with modified macrophages, lymphocytes and giant cells (Ref: Robbins 9/e p208. 375,376; Anananantyan 9/e p162)Clinical features like fever; night sweats and weight loss and X-ray finding of mass in apical lobe with histopathological findings of caseous necrosis are highly suggestive of tuberculosis. The underlying process is type IV hypersensitivity, which is characterized by presence of modified macrophages, lymphocytes & giant cells.Schematic illustration of the events that give rise to the formation of granulomas in cell-mediated (type IV) hypersensitivity reactions.TuberculosisAntigenic property :Group specificity is due to polysaccharideQ while type specificity is due to protein antigenQ.Antibodies are not useful for diagnosis and immunity.Pathogenecity:Macrophages are the primary cells infectedQ by M. tuberculosis.M. tuberculosis replicated within the macrophages (phagosome) by blocking fusion of phagosome and IysosomeQ.It is due to escape of kiliing by macrophagesQ and induction of type IV hypersensitivity.Factors contributing in pathogenesis: Cord factor, Lipoarabinomannan, Complement system, M. tuberculosis heat shock proteins.Risk of acquiring infection is determined mainly by exogenous factorsQ while risk of developing disease depends largely on endogenous factorsQ.Most potent risk factor- HIV coinfectionQClinical Features:Pulmonary TBExtrapuimonary TBPrimary diseasePost primary disease* MC site: Lymph nodeQ (MC cervical & supraclavicular)* Involvement of genitourinary tract (sterile pyuria in acidic urine)* Skeletal TB (MC site spine, hip, knee)* TB meningitis (paresis of cranial nerves especially ocular, is frequent* finding)Q* Gl TB (MC site terminal ileum & caecum)Q* Tuberculous pericarditis (MC cause of chronic constrictive pericarditis)Q* Usually localized in middle & lower zonesQ* Primary focus is usually peripheral in subpleural region and is accompanied by draining lymphatics, inflamed regional LNs which are collectively called Primary complex / Ghon's focusQ.* Occult hematogenous dissemination to apex of lung (Simons FocusQ)* Also called adult type or reactivation or secondary tuberculosis or chronic pulmonary TB* Usually localized to apical & posterior segments of upper lobe due to high O2 concentration (Puhl's lesionQ)* MC hematologic finding: mild anemia & leukocytosis* Infraclavicular lesion is called Assman's FocusQ
Enzymatic degeneration
Acute decrease in blood supply
Decreased supply of growth factor
Hypersensitivity reaction with modified macrophages, lymphocytes and giant cells
Immunity