Pathology of Restrictive Lung Diseases

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Pathology of Restrictive Lung Diseases

• Dr. Mohammed Iqbal Musani, MD

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Restrictive Lung Diseases.Definition

• Restrictive lung diseases are characterized by
  reduced compliance (i.e., more pressure is
  required to expand the lungs because they are
  stiff).
• Although chest wall abnormalities, some of which
  were mentioned earlier, can also cause
  restrictive disease, this discussion will
  concentrate on parenchymal causes.

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• Before we discuss the individual disorders, it is
  useful to consider two general features of
  restrictive pulmonary diseases, beginning with a
  brief review of the microanatomy of the septal
  wall
• only a thin basement membrane, and the cytoplasm
  of two very flat cells, endothelium and alveolar
  epithelium, are interposed between air and blood.
• The initiating injury in these diseases usually
  affects either of these two cell types, although,
  with chronicity, changes in the interstitium tend
  to dominate the picture.
• Because of prominent changes in the interstitium,
  these disorders are often referred to as
  interstitial lung disease.

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Signs Symptoms

• The important signs and symptoms of restrictive
  lung disease can be inferred from the morphologic
  changes.
• Interstitial fluid or fibrosis produces a "stiff
  lung," which in turn reduces lung compliance and
  necessitates increased effort of breathing
  (dyspnea).

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• Furthermore, damage to the alveolar epithelium
  and interstitial vasculature produces
  abnormalities in the ventilation-perfusion ratio,
  leading to hypoxia.
• For example, damaged or underventilated air units
  (alveoli) may still be perfused, and, conversely,
  with damage to the capillaries, underperfusion of
  ventilated airspaces occurs.

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Classification

• Restrictive lung disease can be either
• (1) acute, associated with an abrupt decrease in
  respiratory function and demonstrable pulmonary
  edema, often with accompanying inflammation,
• (2) chronic, associated with insidious
  development of respiratory dysfunction. Chronic
  restrictive lung disorders demonstrate variable
  amounts of chronic inflammation and fibrosis

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CHRONIC RESTRICTIVE LUNG DISEASES

• The chronic restrictive (interstitial) diseases
  of the lung parenchyma are a heterogeneous group
  with little uniformity regarding terminology and
  classification. Many entities are of unknown
  cause and Unknown pathogenesis

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• Table 13-2. SELECTED CAUSES OF CHRONIC
  INTERSTITIAL LUNG DISEASE
• Occupational and Environmental Exposure
• Inorganic  Asbestosis  Silicosis  Coal workers'
  pneumoconiosis
• Organic  Hypersensitivity pneumonitis
• Drug or Treatment RelatedChemotherapeutic
  agents  Busulfan  Bleomycin  MethotrexateIonizing
  radiationOxygen
• Immunologic Lung Disease
• SarcoidosisWegener granulomatosisCollagen
  vascular diseases  Systemic lupus
  erythematosus  Rheumatoid arthritis  Scleroderma  
  Dermatomyositis-polymyositisGoodpasture
  syndromeAllograft rejection
• Miscellaneous Post acute respiratory distress
  syndrome Idiopathic pulmonary fibrosis

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Idiopathic Pulmonary Fibrosis

• Idiopathic pulmonary fibrosis (IPF)-also known as
  cryptogenic fibrosing alveolitis-refers to a
  pulmonary disorder of unknown etiology
  characterized histologically by diffuse
  interstitial fibrosis, which in advanced cases
  results in severe hypoxemia and cyanosis.
• Males are affected more often than are females,
  and approximately two thirds of patients are
  older than 60 years of age at presentation.
• It should be stressed that similar clinical and
  pathologic findings may be noted with
  well-defined entities such as asbestosis, the
  connective tissue diseases, and a number of other
  conditions.
• Therefore, known causes must be ruled out before
  the appellation of "idiopathic" is used.

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Hypersensitivity Pneumonitis

• Hypersensitivity pneumonitis is an
  immunologically mediated inflammatory lung
  disease that primarily affects the alveoli and is
  therefore often called allergic alveolitis. Most
  often it is an occupational disease that results
  from heightened sensitivity to inhaled antigens
  such as moldy hay (Table 13-3). Unlike bronchial
  asthma, in which bronchi are the focus of
  immunologically mediated injury, the damage in
  hypersensitivity pneumonitis occurs at the level
  of alveoli

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Clinical picture

• Hypersensitivity pneumonitis may present either
  as an acute reaction with fever, cough, dyspnea,
  and constitutional complaints 4 to 8 hours after
  exposure or as a chronic disease with insidious
  onset of cough, dyspnea, malaise, and weight
  loss. Several lines of evidence suggest that
  hypersensitivity pneumonitis is an
  immunologically mediated disease

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Sarcoidosis

• Although considered here as an example of a
  restrictive lung disease, it should be remembered
  that sarcoidosis is a multisystemic disease of
  unknown etiology characterized by noncaseating
  granulomas in many tissues and organs.
• Bilateral hilar lymphadenopathy or lung
  involvement (or both), visible on chest
  radiographs, is the major presenting
  manifestation in most cases.
• .

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Etiology and Pathogenesis

• Although the etiology of sarcoidosis remains
  unknown.

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MORPHOLOGY

• The histopathologic feature of sarcoidosis is the
  noncaseating epithelioid granuloma, irrespective
  of the organ involved.
• Discrete, compact collection of epithelioid
  histiocytes-highly differentiated mononuclear
  phagocytes-rimmed by an outer zone of largely
  CD4 helper T cells..

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Clinical Course

• In many patients the disease is entirely
  asymptomatic, discovered on routine chest films
  as bilateral hilar adenopathy or as an incidental
  finding at autopsy.
• In others, peripheral lymphadenopathy, cutaneous
  lesions, eye involvement, splenomegaly, or
  hepatomegaly may be presenting manifestations.