Pathophysiology of Common Diseases of Upper Respiratory Tract, Lecture notes of Law

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Pathophysiology of Common

Diseases of Upper Respiratory

Tract

By: Dr. Milkias (Pathology Resident)

Common Cold(Infectious Rhinitis)

• (^) A viral illness in which the symptoms of rhinorrhea and

nasal obstruction are prominent; systemic symptoms

and signs such as myalgia and fever are absent or mild.

• (^) It is often termed rhinitis but includes self-limited

involvement of the sinus mucosa and is more correctly

termed rhinosinusitis.

• (^) ETIOLOGY.
• (^) The most common pathogens associated with the

common cold are the rhinoviruses, but the syndrome

can be caused by many different viruses

Epidemiology

• (^) Colds occur year-round, but the incidence is

greatest from the early fall until the late spring

• (^) Incidence in Young children is on an average 6–

colds per year but 10–15% of children have at

least 12 infections per year.

• (^) Adults have 2-3 illness per yr.
• (^) Children in daycare centers during the 1st year of

life have 50% more colds than children cared at

home.

Pathophysiology

• (^) During the initial acute stages, the nasal

mucosa is thickened, edematous, and red

• (^) the nasal cavities are narrowed; and the

turbinates are enlarged.

• (^) These changes may extend, to produce

pharyngotonsillitis.

• (^) Secondary bacterial infections also occur

Diagnosis

• (^) Common cold is diagnosed clinically
• (^) differentials

Allergic rhinitis Prominent itching and sneezing

Nasal eosinophils

Foreign body Unilateral, foul-smelling secretions

Bloody nasal secretions

Sinusitis Presence of fever, headache or facial pain,

or periorbital edema or persistence of

rhinorrhea or cough for >14 days

Streptococcosis Nasal discharge that excoriates the nares

Pertussis Onset of persistent or severe cough

Congenital syphilis Persistent rhinorrhea with onset in the 1st 3

mo of life

Complications

• (^) Otitis media
• (^) Sinusitis
• (^) Exacerbation of bronchial asthma
• (^) Pneumonia
• (^) Diarrhea

Treatment : Supportive care

Chronic Rhinitis

• (^) Chronic rhinitis is a squeal to repeated attacks

of acute rhinitis, either microbial or allergic in

origin, with the eventual development of

superimposed bacterial infection

Nasal Polyps

• (^) Recurrent attacks of rhinitis may eventually lead to

focal protrusions of the mucosa, producing socalled

nasal polyps, which may reach 3 to 4 cm in length.

• (^) On histologic examination these polyps consist of

edematous mucosa having a loose stroma, often

harboring hyperplastic or cystic mucous glands,

infiltrated with a variety of inflammatory cells,

including neutrophils, eosinophils, and plasma cells

with occasional clusters of lymphocytes

Cont’d…

• (^) Differentiating bacterial sinusitis from a cold may be

difficult, but certain patterns suggestive of sinusitis have

been identified.

• (^) These include persistence of nasal congestion,

rhinorrhea (of any quality) and daytime cough ≥10 days

without improvement; severe symptoms of temperature

≥39°C (102°F) with purulent nasal discharge for 3 days or

longer; and worsening symptoms either by recurrence of

symptoms after an initial improvement or new

symptoms of fever, nasal discharge and daytime cough.

Cont’d…

• (^) the infections have the potential of spreading into

the orbit or of penetrating into the surrounding

bone to give rise to osteomyelitis or spreading into

the cranial vault, causing septic thrombophlebitis of

a dural venous sinus, brain abscess and meningitis.

• (^) Rx : Initial therapy with amoxicillin (50 mg/kg/day

divided bid) is adequate for the majority of children

with uncomplicated mild to moderate severity acute

bacterial sinusitis

Tonsillopharyngitis/pharyngotonsillitis.

• (^) Pharyngitis and tonsillitis are frequent features of viral

upper respiratory infections.

• (^) Most commonly implicated are the rhinoviruses,

echoviruses, and adenoviruses, and, less frequently,

respiratory syncytial viruses and the various strains of

influenza virus.

• (^) In the usual case, there is reddening and edema of the

nasopharyngeal mucosa, with reactive enlargement of

nearby tonsils and lymph nodes.

• (^) Bacterial infections may be superimposed on these viral

infections, or may be primary invaders.

EPIDEMIOLOGY.

• (^) Viral upper respiratory tract infections are spread by

close contact and occur most commonly in fall, winter,

and spring.

• (^) Streptococcal pharyngitis is uncommon before 2–3 yr

of age, has a peak incidence in the early school years,

and declines in late adolescence and adulthood.

• (^) Illness occurs most often in winter and spring and

spreads among siblings and classmates.

• (^) Primary infection with HIV also manifests with

pharyngitis and a mononucleosis-like syndrome.

PATHOGENESIS OF GABHS.

• (^) Colonization of the pharynx by GABHS can result in either

asymptomatic carriage or acute infection.

• (^) The M protein is the major virulence factor of GABHS and

facilitates resistance to phagocytosis by polymorphonuclear

neutrophils.

• (^) Scarlet fever is caused by GABHS that produces 1 of 3

streptococcal erythrogenic exotoxins (A, B, and C) that can induce

a fine papular rash.

• (^) Exotoxin A appears to be most strongly associated with scarlet

fever.

• (^) Exposure to each exotoxin confers specific immunity only to that

toxin and, therefore, scarlet fever can occur up to 3 times.