German measles (rubella)
 - sometimes called "three day measles".
 - incubation 14-21 days; infectious 7 days before the rash and 14 days after the onset of the rash.
 - in adults, rubella present with fever, headache, and painful postauricular Lymphadenopathy 1 to 2 days prior to the onset of rash, while in children, the rash is usually the first sign.
 - rash (vasculitis) consists of tiny red to pink macules (not raised) that begins on the head and spreads downwards and disappears over the ensuing 1-3 days; rash tends to become confluent.
 - 1/3rd of young women develop arthritis due to immune-complexes.
 - splenomegaly (50%) 

EMBOLISM

Definition: transportation of an abnormal mass of an abnormal mass of undissolved material from one part of circulation to another. The mass transported is called embolus.

Types
I .Thrombi and clots.
2. Gas or air.
3. Fat
4.Amniotic fluid.
5.Tumour

Thromboembolism 
This is the commonest type of embolus and may be formed of the primary thrombus  or more often of propagated clot region which is loosely attached.

Emboli from venous thrombi can result In impaction in the pulmonary  arteries and result in sudden death.
Embolism from cardiac or arterial thrombi results in systemic embolism causing infraction and gangrene.

Gaseous
This occurs when gas is introduced into the circulation:
•    Accidental opening of large veins during surgery.
•    Mismanaged transfusion. .
As air is  readily absorbed into blood only  sudden introduction or large quantities of air produces effects
Caisson’s Disease  bubbling of nitrogen from the blood during sudden decompression as seen during deep sea diving.

Fat Embolism
Causes
•    Fractures especially of long bones and multiple
•    Crush injuries.

Sites of impaction:

o    Lungs.
o    Systemic: causing -
    →    petechial skin haemorrhages.
    →    Embolism to brain leading to coma and death.
    →     Conjunctival and retinal haemorrhages
    
Tumor Embolism.

Invasion of vascular channe1.s is a feature of malignant neoplasms and this leads to:
•    Metastatic deposits,
•    DlC
 

Erythema multiforme is a hypersensitivity reaction to an infection (Mycoplasma), drugs or various autoimmune diseases.
 - probable immunologic disease
 - lesions vary from erythematous macules, papules, or vesicles.
 - papular lesions frequently look like a target with a pale central area.
 - extensive erythema multiforme in children is called Stevens-Johnson syndrome, where there is extensive skin and mucous membrane involvement with fever and respiratory symptoms.

PERTUSSIS (Whooping Cough)

An acute, highly communicable bacterial disease caused by Bordetella pertussis and characterized by a paroxysmal or spasmodic cough that usually ends in a prolonged, high-pitched, crowing inspiration (the whoop).

Transmission is by aspiration of B. pertussis

Symptoms and Signs

The incubation period averages 7 to 14 days (maximum, 3 wk). B. pertussis invades the mucosa of the nasopharynx, trachea, bronchi, and bronchioles, increasing the secretion of mucus, which is initially thin and later viscid and tenacious. The uncomplicated disease lasts about 6 to 10 wk and consists of three stages: catarrhal, paroxysmal, and convalescent.

Fulminant hepatitis

Fulminant hepatitis leads to submassive and massive hepatic necrosis. 
a. Etiology. HAV, HBV, HCV, delta virus (HDV) superinfection, HEV, chloroform, carbon tetrachloride, isoniazid, halothane, and other drugs (acetaminophen overdose) all may cause fulminant hepatitis.
b. Clinical features include progressive hepatic dysfunction with a mortality of 25%-90%.
c. Pathology

(1) Grossly, one sees progressive shrinkage of the liver as the parenchyma is destroyed. 

THE THYROID GLAND

The thyroid gland develops embryologically from the developing pharyngeal epithelium that descends from the foramen cecum at the base of the tongue to its normal position in the anterior neck. This pattern of descent explains the occasional presence of ectopic thyroid tissue, most commonly located at the base of the tongue (lingual thyroid) or at other sites abnormally high in the neck.