Skin: Rocky Mountain Spotted Fever

Lab 9, Case 1

Skin biopsy

Note area of hemorrhage (arrow) in the dermis

Hemorrhage immediately underneath the epidermis

Also note the cellularity and thrombosis of the small vessels in the dermis (arrow)

Small vessel in the dermis with mild vasculitis

Dermal vessel with mild vasculitis

Dermis with an area of more severe vasculitis (arrow)

Severe vasculitis in the dermis

Dermal vessel (arrow) which is exhibiting vasculitis and thrombosis

Thrombosed vessel in the dermis

Note that the endothelial cells are missing along part of the circumference of the vessel (arrows). This is where the main part of the thrombus has attached. Also note the inflammation surrounding the vessel.

Brain: Bacterial Meningitis

Lab 9, Case 2

Autopsy specimen

Purulent exudate (arrows) in the leptomeninges

Exudate (1) in the meninges and congestion in the vessels (2) in the leptomeninges

Congested blood vessel

Inflammatory exudate is present within the vessel and throughout the leptomeninges

Sulcus

Congested vessels and inflammatory exudate in the leptomeninges

Inflammatory exudate within a sulcus

The majority of cells in this exudate are neutrophils. There is also abundant fibrin (arrows) and red blood cells are present in the congested vessels.

A blood vessel from the previous image

The vessel is surrounded by neutrophils (arrows).

Exudate from the leptomeninges which has been Gram-stained

Note the Gram-negative bacteria (arrows) throughout this section.

Brain tissue with diffuse edema

Trachea: Diphtheria

Lab 9, Case 3

Trachea with diptheritic membrane (1), which has pulled away from the tracheal lining during histological processing

Note the tracheal cartilage (2) present in this section.

Trachea with diptheritic membrane (1)

Even though the main part of the membrane has pulled away from the tracheal lining during histological processing, in this section part of the membrane is still loosely attached. Once again, note the tracheal cartilage (2).

Tracheal mucosa and diptheritic membrane

The mucosal surface of the trachea is ulcerated (total loss of epithelial cells) and the only remaining epithelial cells are found in the glands (arrows). The diptheritic membrane consists of fibrin and inflammatory cells, most of which are dead.

Higher power of previous image showing the ulcerated tracheal mucosa and the diptheritic membrane

Although difficult to make out at this magnification, most of the cells in this inflammatory exudate are neutrophils.

Heart: Acute Rheumatic Myocarditis

Lab 9, Case 4

Mitral valve demonstrating marked thickening and fibrosis of the valve leaflet

There are also numerous foci of fibrinoid necrosis within the cusps and friable vegetations (verrucae) along the lines of closure (arrows). These irregular, warty projections are found at sites of erosion on the inflammed endocardial surface. The verrucae probably result from the precipitation of fibrin where the leaflets impinge on each other.

Relatively normal looking heart tissue

Cellular accumulations- Aschoff bodies (arrows)- within the interstitum of the myocardium

These are found especially around blood vessels.

Myocardium containing Aschoff bodies (arrows) within the intersitium

Cellular detail of Aschoff bodies

Aschoff bodies are foci of fibrinoid necrosis surrounded by lymphocytes, macrophages, an occasional plasma cell, and plump “activated” histiocytes called Anitschkow cells or Aschoff cells (arrows). These distinctive cells have abundant amphophilic cytoplasm and central round-to-ovoid nuclei in which the chromatin is disposed in a central, slender, wavy ribbon resembling a caterpillar (hence the designation “caterpillar cells”).

Myocardium

Cellular detail of Aschoff body

In this case there appears to be a multinucleated Aschoff giant cell (arrow).

Clostridial Myonecrosis

Lab 9, Case 5

Taken at autopsy

Notice the swelling and the area of primary infection (arrow)

Hemorrhagic blebs (arrows) on the skin

The blebs on the skin are accumulations of gas being discharged into the tissues from the Clostridium perfringens. The gas produces crepitance.

Muscle fascicles containing large gas bubbles (arrows)

Note that there is no inflammatory reaction in this section.

Skeletal muscle

The muscle cells are hypereosinophilic and most do not contain nuclei, indicating these cells are dead or dying. The round clear spaces (1) in this tissue correspond to gas accumulations prior to death. In between the bundles of muscle cells, accumulations of small dark blue-staining bacterial organisms can be seen (2). Also note that there is no inflammatory response in this tissue.

Gas accumulation is present in this tissue. 1: Necrotic muscle cell

2: Mild inflammatory response 3: Thrombosed blood vessel

The blue-staining rods (bacterial organisms) can barely be appreciated at this magnification.

Higher-power of previous image provides clearer view of gas bubbles in the tissue, the necrotic hypereosinophilic muscle cell (1), and the mild inflammatory reaction (2)

At this magnification, the bacteria located throughout this section can be better appreciated.

Stained with tissue Gram stain (Brown and Brenn)

The Gram-positive bacilli can be seen throughout this section.

Actinomycosis

Lab 9, Case 6

Retroperitoneal abscess

At this magnification, multiple dark-staining foci can be appreciated. These foci are Actinomyces colonies (arrows). These colonies are known as “sulfur granules” because in gross specimens they are visible to the naked eye as yellow grains, thus resembling grains of sulfur.

Abscess demonstrating a pocket of purulent exudate that contains numerous actinomycotic colonies (arrows).

Actinomycotic colonies in the abscess

Actinomycotic colonies in the abscess

The filamentous nature (arrows) of the actinomyces organisms in these colonies can be appreciated.

Actinomycotic colony

The filamentous nature (arrows) of the actinomyces organisms is more easily appreciated.