Chickenpox (varicella)
 - primarily a childhood disease (70%)
 - incubation period 14-16 days; highly contagious; infectious 2 days before the vesicles until the last one dries.
 - present with generalized, intensely pruritic skin lesions starting as macules vesicles pustules (MVP-most valuable player) usually traveling centrifugally to the face and out to the extremities; unlike smallpox vesicles, chickenpox vesicles appear in varying stages of development as successive crops of lesions appear; intranuclear inclusions similar to HSV.
 - pneumonia develops in 1/3 of adults; MCC death in chickenpox.
 - association with Reye's syndrome if child takes aspirin. 

Rocky Mountain Spotted Fever (Spotted Fever; Tick Fever; Tick Typhus)

An acute febrile disease caused by Rickettsia rickettsii and transmitted by ixodid ticks, producing high fever, cough, and rash.

Symptoms and Signs

The incubation period averages 7 days but varies from 3 to 12 days; the shorter the incubation period, the more severe the infection. Onset is abrupt, with severe headache, chills, prostration, and muscular pains. Fever reaches 39.5 or 40° C (103 or 104° F) within several days and remains high (for 15 to 20 days in severe cases),

Between the 1st and 6th day of fever, most patients develop a rash on the wrists, ankles, palms, soles, and forearms that rapidly extends to the neck, face, axilla, buttocks, and trunk. Often, a warm water or alcohol compress brings out the rash. Initially macular and pink, it becomes maculopapular and darker. In about 4 days, the lesions become petechial and may coalesce to form large hemorrhagic areas that later ulcerate

Neurologic symptoms include headache, restlessness, insomnia, delirium, and coma, all indicative of encephalitis. Hypotension develops in severe cases. Hepatomegaly may be present, but jaundice is infrequent. Localized pneumonitis may occur. Untreated patients may develop pneumonia, tissue necrosis, and circulatory failure, with such sequelae as brain and heart damage. Cardiac arrest with sudden death occasionally occurs in fulminant cases.

Multiple sclerosis
a. A demyelinating disease that primarily affects myelin (i.e. white matter). This affects the conduction of electrical impulses along the axons of nerves. Areas of demyelination are known as plaques.
b. The most common demyelinating disease.
c. Onset of disease usually occurs between ages 20 and 50; slightly more common in women.
d. Disease can affect any neuron in the central nervous system, including the brainstem and spinal cord. The optic nerve (vision) is commonly affected.

Peutz-Jeghers syndrome
1. Lesions appear as small, melanotic, and freckle-like. They can be found on the skin, oral mucosa, lips, feet, and hands. 
2. May also present with intestinal polyps, which may develop into a gastrointestinal carcinoma. 
3. Genetic transmission: autosomal dominant.

ANAEMIA
Definition. Reduction of the hemoglobin level below the normal for the age and sex of the patient

Classification
1. Blood loss anaemia:
- Acute.
- Chronic (results in iron deficiency).

2. Deficiency anaemia:

- Iron deficiency.
- Megaloblastic anaemia-BI2 and Folic acid deficiency.
- Protein deficiency.
- Scurvy-Vitamin C deficiency.

3. Marrow dysfunction:
- Aplastic anaemia.
- Marrow infiltration.
- Liver failure.
- Renal failure.
- Collagen diseases.

4 Increased destruction (Heamolysis)
- Due to corpuscular defects.
- Due to extra corpuscular defects
 

Pemphigus
1. Ulcerative lesions on the skin and oral mucosa.
2. An autoimmune disease in which patients have autoantibodies against hemidemosomal attachment of epidermis cells.
3. Histologically characterized by acantholysis, in which epidermal cells appear to detach and separate from each other, as seen by Tzanck smears.
4. Can be life-threatening if untreated.
5. A positive Nikolsky sign is observed.
Because of sloughing of the epidermis, a red blister forms after pressure is applied to affected skin.
6. Treatment: corticosteroids.