Lichen planus is an itchy, violaceous, flat-topped papule highlighted by white dots or lines called Wickham's striae.
 - lichen planus may occur in the oral mucosa, where it has a fine white net-like appearance.
 - increased epidermal proliferation; ? immunologic; initiated by epidermal injury from drugs, viruses, or topical agents.
 - characteristic histologic features include:
 - hyperkeratosis
 - absence of parakeratosis
 - prominent stratum granulosum
 - an irregular "saw toothed" accentuation of the rete pegs. 

 - dermal-epidermal junction obscured by a band-like infiltrate of lymphocytes.
 - It is generally self-limiting and resolves spontaneously 1 to 2 years after onset; however, the oral lesions may persist for years.

Monocytosis:
Causes

-Infections causing lymphocytosis, especialy tuberculosis and typhoid. 
-Monocytic leukaemia.
-Some auto immune diseases.

Roseola
 - alias exanthem subitum; caused by Herpes virus type 6.
 - children 6 months to 2 years old; spring and fall; incubation 10-15 days.
 - sudden onset of a high fever with absence of physical findings; febrile convulsions are particularly common.
 - fever falls by crisis on the 3rd or 4th day → 48 hours after temperature returns to normal macular or maculopapular rash starting on the trunk and spreading centrifugally.

CONGESTION

Congestion or hyperaemia means an increase in the content of blood in an organ. It may be :

A. Active - due to increased arterial flow to the organ with dilatation of micro vessels as in

• Inflammation.
• Increased metabolic activity.
• Neurogenic blushing.

B. Passive - due to decreased venous drainage resulting in pooling of blood. There is always an associated element of oedema.

STOMACH 
Congenital malformations

1. Pyloric stenosis 

Clinical features. Projectile vomiting 3-4 weeks after birth associated with a palpable "olive" mass in the epigastric region is observed. 
Pathology shows hypertrophy of the muscularis of the pylorus and failure to relax. 

2. Diaphragmatic hernias are due to weakness in or absence of parts of the diaphragm, allowing herniation of the abdominal contents into the thorax. 

Inflammation 

1. Acute gastritis (erosive)

Etiology. Alcohol, aspirin and other NSAIDs, smoking,  shock, steroids, and uremia may all cause disruption of the mucosal barrier, leading to inflammation. 
Clinical features. Patients experience heartburn, epigastric pain, nausea, vomiting, hematemesis, and even melena. 

2. Chronic gastritis (nonerosive) may lead to atrophic mucosa with lymphocytic infiltration. 

Types 

(1) Fundal (Type A) gastritis is often autoimmune in origin.  It is the type associated with pernicious anemia and, therefore, achlorhydria and intrinsic factor deficiency. 
(2) Antral (Type B) gastritis is most commonly caused by Helicobacter pylori and is the most common form of chronic gastritis in the U.S. H. pylori is also responsible for proximal duodenitis in regions of gastric metaplasia.

Clinical features. The patient may be asymptomatic or suffer epigastric pain, nausea, vomiting, and bleeding. Gastritis may predispose to peptic ulcer disease, probably related to  H. pylori infection.

3. Peptic ulcers

Peptic ulcers are usually chronic, isolated ulcers observed in  areas bathed by pepsin and HCI; they are the result of mucosal breakdown

Common locations are the proximal duodenum, the stomach, and the esophagus, often in areas of Barrett's esophagus. 

Etiology. There are several important etiologic factors. 
Duodenal ulcers occur predominantly in patients with excess acid secretion, while gastric ulcers usually occur in patients with lower than average acid secretion. 

Other predisposing conditions include smoking, cirrhosis, pancreatitis, hyperparathyroidism, and H. pylori infection. Aspirin, steroids, and NSAlDs are known to be assoicated with peptic ulcer disease. Next to H. pylori colonization, aspirin or NSAID ingestion is the most common cause of peptic ulcer. 

Clinical features. Patients experience episodic epigastric pain. Duodenal and most gastric ulcers are relieved by food or antacids. Approximately one-fifth of gastric ulcer patients get no relief from eating or experience pain again  within 30 minutes.

Pathology. Benign peptic ulcers are well-circumscribed  lesions with a loss of the mucosa, underlying scarring, and sharp walls. 

Complications include hemorrhage, perforation, obstruction, and pain. Duodenal ulcers do not become malignant .Gastric ulcers do so only rarely; those found to be ma1ignant likely originated as a cancer that ulcerated.

Diagnosis is made by upper gastrointestinal Series , endoscopy, and biopsy to rule out malignancy or to demonstrate the presence of H. pylori. 

4. Stress ulcers 

are superficial mucosal ulcers of the stomach or duodenum or both. Stress may be induced by burns, sepsis shock, trauma, or increased intracranial pressure. 

Tumors 
1. Benign 

a. Leiomyoma, often multiple, is the most common benign neoplasm of the stomach. Clinical features include bleeding, pain, and iron deficiency anemia. 

b. Gastric polyps are due to proliferation of the mucosal epithelium. 

2. Malignant tumors 

a. Carcinoma 

Etiology. Primary factors include genetic predisposition and diet; other factors include hypochlorhydria, pernicious anemia, atrophic gastritis, adenomatous polyps, and exposure to nitrosamines. H. pylori are also implicated. 

Clinical features. Stomach cancer is usually asymptomatic until late, then presents with anorexia, weight loss, anemia, epigastric pain, and melena. Virchow's node is a common site of metastasis. 

Pathology. Symptomatic late gastric carcinoma may be expanding or infiltrative. In both cases the prognosis is poor (approximately 10% 5-year survival), and metastases are frequently present at the time of diagnosis. 
Adenocarcinomas are most common. 

b. Gastrointestinal lymphomas may be primary In the gastrointestinal tract as solitary masses. 

c. Sarcoma is a rare, large, ulcerating mass that extends into the lumen. 

d. Metastatic carcinoma. Krukenberg's tumor is an ovaria metastasis from a gastric carcinoma. 

e. Kaposi's sarcoma. The stomach is the most commonly involved GI organ in Kaposi's sarcoma. It primarily occurs in homosexual men, appearing as hemorrhagic polypoid, umbilicated nodular lesions, typically in a submucosal location. It rarely causes symptoms

ESOPHAGUS Pathology

Congenital malformations 
1. A tracheoesophageal fistula (the most prevalent esophageal anomaly) occurs most commonly as an upper esophageal blind pouch with a fistula between the lower segment of the esophagus and the trachea. It is associated with hydramnios, congenital heart disease, and other gastrointestinal malformation. 

2. Esophageal atresia is associated with VATER syndrome (vertebra1 defects, anal atresia, tracheoesophageal fistula, and renal dysplasia)

3. Stenosis refers to a narrowed esophagus with a small lumen.  lt may be congenital or acquired, e.g., through trauma or inflammation. 

Inflammatory disorders 

Esophagitis 

most often involves the lower half of the esophagus.  Caused by the reflux of gastric contents (juices) into the lower esophagus. One of the most common GI disorders.

Clinical features. 

Patients experience substernal burning  associated with regurgitation, mild anemia, dysphagia,  hematemesis, and melena. Esophagitis may predispose to esophageal cancer. 

Etiology

- Reflux esophagitis is due to an incompetent lower esophageal sphincter that permits reflux of gastric juice into the lower esophagus. 
- Irritants such as citric acid, hot liquids, alcohol, smoking, corrosive chemicals, and certain drugs, such as tetracycline, may provoke inflammation. 
- Infectious etiologies include herpes, CMV, and C. albicans. The immunocompromised host is particularly susceptible to infectious esophagitis. 
Although chronic or severe reflux disease is uncommon, consequences of these conditions can lead to Barrett’s esophagus, development of a stricture, or hemorrhage.

Pathology

-Grossly, there is hyperemia, edema, inflammation, and superficial necrosis. 

Complications include ulceration, bleeding, stenosis, and squamous carcinoma. 

Treatment: diet control, antacids, and medications that decrease the production of gastric acid (e.g., H blockers).

Barrett's esophagus, 

gastric or intestinal columnar epithelium replaces normal squamous epithelium in response to  chronic reflux.- A complication of chronic gastroesophageal reflux disease.
- Histologic findings include the replacement of squamous epithelium with metaplastic columnar epithelium.
- Complications include increased incidence of esophageal adenocarcinoma, stricture formation, or hemorrhage (ulceration).

 Motor disorders. 

Normal motor function requires effective peristalsis and relaxation of the lower esophageal sphincter. 

Achalasia is a lack of relaxation of the lower esophageal sphincter (LES), which may be associated with aperistalsis of the esophagus and increased basal tone of the LES. 

Clinical features. Achalasia occurs most commonly between the ages of 30 and 50. Typical symptoms are dysphagia, regurgitation, aspiration, and chest pain. The lack of motility promotes stagnation and predisposes to carcinoma. 

Hiatal hernia is the herniation of the abdominal esophagus, the stomach, or both, through the esophageal hiatus in the  diaphragm.

Scleroderma is a collagen vascular disease, seen primarily in women, that causes subcutaneous fibrosis and widespread  degenerative changes. (A mild variant is known as CREST syndrome which stands for calcinosis. raynaud's phenomenon , esophageal dysfunction, sclerodactyly and telengectseia. esophagus is the most frequently involved region of the gastrointestinal tract.

Clinical features are mainly dysphagia and heartburn due to reflux oesophagitis caused by aperlistalsis and incompetent LES. 

Rings and webs 

1. Webs are mucosal folds in the upper esophagus above the aortic arch. 
2. Schatzki rings are mucosal rings at the squamocolumnarjunction below the aortic arch.
3. Plummer Vinson Syndrome consist of triad of dysphagia, atrophic glossitis, and anemia. Webs are found in the upper esophagus. The syndrome is associated specifically with iron deficiency anemia and sometimes hypochlorhydria. Patients are at increased risk for carcinoma of the pharynx or esophagus. 

Mallory-Weiss syndrome
Mallory-Weiss tears refers to small mucosal tears at the gastroesophageal junction secondary to recurrent forceful vomiting. The tears occur along the long axis an result in hematemesis (sometimes massive).

- Characterized by lacerations (tears) in the esophagus.
- Most commonly occurs from vomiting (alcoholics).
- A related condition, known as Boerhaave syndrome, occurs when the esophagus ruptures, causing massive upper GI hemorrhage.

Esophageal varices
- The formation of varices (collateral channels) occurs from portal hypertension.
Causes of portal hypertension include blockage of the portal vein or liver disease (cirrhosis).
- Rupture of esophageal varices results in massive hemorrhage into the esophagus and hematemesis.
- Common in patients with liver cirrhosis.

Diverticula 
are sac-like protrusions of one or more layers of  pharyngeal or esophageal wall. 

Tumors 
- Benign tumors are rare. 
- Carcinoma of the esophagus most commonly occurs after 50 and has a male:female ratio of 4.1. 

Etiology: alcohal ingestion, smoking, nitrosamines in food, achalasia , web ring, Barrettes esophagus, and deficiencies of vitamins A and C , riboflavin, and some trace minerals

Clinical features include dysphagia (first to solids), retrosternal pain, anorexia, weight loss, melena, and symptoms secondary to metastases. 

Pathology 

- 50% occur in the middle third of the esophagus, 30% in the lower third, and 20% in the upper third. Most esophageal cancers are squamous cell carcinomas. 
Adenocarcinomas arise mostly out of Barrett's esophagus.

Prognosis

is poor. Fewer than 10% of patients survive 5 years, usually because diagnosis is made at a late stage. The  most common sites of metastasis are the liver and lung. The combination of cigarette smoking and alcohol is particularly causative for esophageal cancer (over l00%  risk compared to nondrinkers/nonsmokers).