STREPTOCOCCAL INFECTIONS

Most streptococci are normal flora of oropharynx

Group A streptococci:  Str. pyogenes

Group B streptococci:  Str. agalactiae

Str. pneumoniae

Strep viridans group

Group D: Enterococcus (lately Strep. Fecalis and E. fecium), causes urinary tract infections,

Valvular disease
A. Generally, there are three types:
1. Stenosis—fibrotic, stiff, and thickened valves, resulting in reduced blood flow through the valve.

2. Regurgitation or valvular insufficiency— valves are unable to close completely, allowing blood to regurgitate.

3. Prolapse—“floppy” valves; may occur with or without regurgitation. The most common valvular defect.

Nevus

A nevus refers to any congenital lesion of the skin, while a nevocellular nevus specifically refers to a benign tumor of neural crest-derived cells that include modified melanocytes of various shapes (nevus cells).
 - nevocellular nevi are generally tan to deep brown, uniformly pigmented, small papules with well-defined, rounded borders.
 - most nevocellular nevi are subdivided into junctional, intradermal, or compound types.
 - most nevocellular nevi begin as junctional nevi with nevus cells located along the basal cell layer producing small, flat lesions, which are only slightly raised. 
- junctional nevi usually develop into compound nevi as nevus cells extend into the underlying superficial dermis forming cords and columns of cells (compound: nevi at junction and in the dermis).
 - eventually, the junctional component of a nevocellular nevus is lost, leaving only nevus cells within the dermis, thus the term intradermal nevus.
 - junctional → compound → intradermal nevus.
 - although uncommon, certain nevi may evolve into a malignant melanoma, particularly those which are congenital and those which are referred to as dysplastic nevi.
 - a dysplastic nevus is commonly associated with patients who have multiple scattered nevi over the entire body (dysplastic nevus syndrome) with individual lesions that have a diameter greater than 1 cm.

Multiple myeloma.

Blood picture:

- Marked rouleaux formation.
- Normpcytic normochromic anaemia.
- There may be leucopenia or leucoery!hrohlastic reaction.
- Atypical plasma cells may be seen in some patients
- Raised ESR
- Monoclonal hypergammaglobulinaemia 
- If light chains are produced in excess, they are excreted in urine as bence jones protein

Bone marrow

- Hyper cellular
- Plasma cells from at least 15 – 30% atypical forms and myeloma cells are seen.
 

Adult Respiratory Distress Syndrome 
A constellation of pathologic and clinical findings initiated by diffuse injury to alveolar capillaries. This syndrome is associated with a multitude of clinical conditions which primarily damage the lung or secondarily as part of a systemic disorder. 

Pathogenesis 
There are many types of injuries which lead to the ultimate, common pathway, i.e., damage to the alveolar capillary unit. The initial injury most frequently affects the endothelium, less frequently the alveolar epithelium. Injury produces increased vascular permeability, edema, fibrin-exudation (hyaline membranes). Leukocytes (primarily neutrophils) plays a key role in endothelial damage. 

Pathology 
Heavy, red lungs showing congestion and edema. The alveoli contain fluid and are lined by hyaline membranes. 

Pathophysiology 
Severe respiratory insufficiency with dyspnea, cyanosis and hypoxemia refractory to oxygen therapy.

Diagnostic techniques used in pathology

The pathologist uses the following techniques to the diagnose diseases:

a. Histopathology

b. Cytopathology

c. Hematopathology

d. Immunohistochemistry

e. Microbiological examination

f. Biochemical examination

g. Cytogenetics

h. Molecular techniques

i. Autopsy