Page 178 - Concise Pathology for Exam Preparation ( PDFDrive )

7 Infections 163

Clinical Features
• Involvement of nasal passages can result in a chronically stuffy nose; and epistaxis may
occur due to mucosal erosion.
• Eye damage can lead to blindness.
• Men with lepromatous leprosy may experience erectile dysfunction (impotence) and
become infertile (testicular involvement).
• Deformities may result from muscle weakness.
Reactions in Leprosy
• During the course of treatment (or even in untreated leprosy), a sudden change in the
status of host immune response may produce leprosy reactions—an acute inflammatory
state. These reactions manifest with fever and inflammation of the skin as well as pe-
ripheral nerves, and may affect the lymph nodes, bone marrow, liver, spleen, joints,
testes, kidneys and anterior chamber of eye.
• Type I reaction: It is a cell-mediated immune reaction (delayed or Type IV hypersensitivity)
to mycobacterial antigens in skin and nerves. It may be upgrading or downgrading de-
pending on the predominantly activated cell type, ie, CD41 T cells or CD81 T cells,
respectively. Patients with borderline disease are usually affected as borderline leprosy is
the most unstable form of leprosy. A downgrading reaction represents a shift towards the
lepromatous pole, and a reversal reaction represents a shift towards tuberculoid pole.
• Type II reaction: Also called erythema nodosum leprosum (ENL), it is a Type III (immune
complex mediated) reaction to mycobacterial antigens, usually seen in lepromatous and
borderline lepromatous subtypes (clinical variants with antigen excess).
Diagnosis
Diagnosis is confirmed by microscopically examining infected skin tissue (either a slit
smear or a skin biopsy).

Q. Write briefly about the aetiology and clinical types of pneumonia.
Ans. Pneumonia is defined as a collection of inflammatory exudate in lung parenchyma
distal to terminal bronchioles, mostly resulting in consolidation (solidification) of lung
part(s).

Classification
1. Aetiological:
a) Community-acquired or acute bacterial pneumonia:
(i) Streptococcus pneumoniae (most common causative organism; typically has
lobar distribution)
(ii) Hemophilus influenzae and Moraxella catarrhalis (complicate COPD)
(iii) Staphylococcus aureus (occurs secondary to viral infections)
(iv) Legionella pneumophilia (seen in organ transplant patients)
(v) Enterobacteriaceae (infect chronic alcoholics)
(vi) Pseudomonas (seen in cystic fibrosis and burn patients)
(vii) Atypical organisms (include Mycoplasma pneumoniae, Chlamydophilia pneu-
moniae, Coxiella burnetii and viruses-respiratory syncytial virus, parainfluenza
virus, human metapneumovirus, influenza A and B, and adenovirus). They are
labelled ‘atypical’ as they are not demonstrable with Gram-stain and do not
grow on routine culture media.
b) Healthcare-associated pneumonia: Distinct clinical entity defined by the following
criteria: hospitalization of at least two days within recent past; attending a long-term
care facility, a hospital or a haemodialysis clinic; recent intravenous antibiotic ther-
apy, wound care or chemotherapy. Causative organisms include
(i) Staphylococcus aureus (methicillin sensitive)
(ii) Staphylococcus aureus (methicillin resistant)
(iii) Pseudomonas species
(iv) Streptococcus pneumoniae

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