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Thursday, February 28, 2013

Cystic fibrosis is an autosomal recessive disease due to mutation in the long arm of chromosome number  7 (in the region 7q31.2) which codes for a critical chloride channel known as cystic fibrosis transmembrane conductance regulator (CFTR) protein.

The most common mutation in norther European and American populations is DF508 (deletion, phenylalanine at position 508).

Cystic fibrosis is the most common fatal genetic disease in Caucasians, with a carrier rate of 1 in 22 and an incidence of about 1 in 2000 live births.

Tuesday, February 26, 2013

Bronchiectasis is abnormal and permanent dilatation of the central and medium-sized airways. This leads to impaired clearance of bronchial secretions with secondary bacterial infection and bronchial inflammation.

Changes in bronchiectasis
Changes in bronchiectasis

Causes of bronchiectasis:

In children:

1. Cystic fibrosis
Changes in airway
2. Congenital ciliary dysfunction syndrome, also known as Kartagener's syndrome or Immotile ciliary syndrome.

In young adults:

1. Pulmonary tuberculosis
2. Inhalation of foreign body

In adults:

1. Pulmonary tuberculosis
2. Ciliary dysfunction syndrome
3. As a complication of Pneumonia, where there is retention of sputum leading to lobar collapse and bronchiectasis.

Myopia is a type of refractive error of eye where parallel rays of light coming from infinity distance (6 m or more) gets focused in front of the retina.

Normal eye and myopia
Normal eye and Myopic eye

Features of Myopia:

1. Image of any object is formed in front of the retina.
2. Near vision is good but distant vision is bad.

Monday, February 25, 2013

Refractive errors: These are disorders of the eye, not diseases.

Emmetropia: A normal eye with no refractive errors is an emmetropic eye. Emmetropia means when parallel rays of light from infinity distance falls on the eye, it can focus them on the retina without any accommodation  Infinity distance in Ophthalmology is defined to be a distance of 6 m or more.
Emmetropia / Normal Vision
Emmetropia / Normal Vision

Ametropia: An eye with refractive errors when viewing objects at infinity distance is an ametropic eye. This eye has to accommodate the parallel rays of light to focus them on the retina.
Refractive Errors of the Eye
Refractive Errors of the Eye

Saturday, February 23, 2013

Hepatitis A virus: (infectious hepatitis):
Structure of Hepatitis A virus


1.    It is a member of picorna group of enterovirus

2.    Single stranded RNA virus with one serotype

3.    Non-enveloped, Icosahedral nucleocapsid

4.    Replicate in the cytoplasm, inactivated by heat

5.    HAV is highly infectious and spread by the faeco-oral route

Some facts about Hepatitis A virus

NOTE: Infected individuals also may be asymptomatic, excrete the virus in faeces for about 2-3 weeks before the onset of symptoms and then for a further 2 weeks or so.

Viral hepatitis is a common cause of jaundice and must be considered in anyone presenting with hepatitis blood test (high aminotransaminase).

All hepatitis virus cause illness and similar clinical and pathological features and are frequently an-icteric or even asymptomatic.

They differ in their tendency to cause acute and chronic infection.

Classification of hepatitis virus:

A. Hepatotrophic / Classical virus:

Five commonly medically important virus are described as hepatotrophic virus as their main site of infection is liver. They are:

Structure of Hepatitis B virus
2.    Hepatitis B virus
3.    Hepatitis C virus
4.    Hepatitis D virus
5.    Hepatitis E virus
6.    Hepatitis G virus

B. Other viruses responsible for hepatitis:

1.    Epstein-Barr virus
2.    Cytomegalo virus
3.    Yellow fever virus
4.    Herpes virus
5.    Rubella virus
6.    Adeno virus

Friday, February 22, 2013

Herpes virus: 

Get to know Herpes virus, its classification, types, usual sites of infection, sites of latency, the diseases caused by herpes virus and their routes of transmission.  Also do you know what is herpes B virus?

Herpes virus is a double stranded DNA enveloped virus.
Structure of Herpes Virus

Properties of herpes virus:

  1. Virion: Spherical
  2. Genome: Double stranded linear DNA
  3. Capsid: Icosahedral
  4. Replication: Occurs within the nucleus and form intranuclear inclusions.
  5. Envelop: The only virus that develops envelop (lipoprotein envelop) from the nuclear membrane by budding.
  6. Enzyme: No viral polymerase enzyme. Uses host cell RNA polymerase.
  7. Serotype: Single.
  8. Size: large, 120-200 nm diameter. Second in size to poxvirus.
  9. Latent infection: Noted for their ability to cause latent infection. In such cases, the acute infection is followed by a period of asymptomatic period during which the virus is in acquiescent (latent) stage. When the patient is exposed to an inciting agent or immunosuppression occurs then reactivation of virus replication and disease can occur. ( Acute disease > asymptomatic period > latent state)
  10. Sensitivity: Ether sensitive.
  11. Giant cell: All produce giant cells.

Properties of dengue virus:

Dengue Virus
1.   Virus of flavivirus family

2.   RNA, enveloped virus

3.   Has 4 serotypes- DEN- 1,2,3,4

4.   Replication is in cytoplasm

5.   Females Aedes Aegypti mosquito transmit the disease

6.   Viraemia is present at the time of fever

Thursday, February 21, 2013

Rota virus

Properties of rota virus:

1.   Family - retrovirus
2.   Non-enveloped, RNA virus
3.   Double stranded, Segmented virus
4.   It is surrounded by a double-layered Icosahedral capsid without an envelop
5.   2 major sub-group, 6 serotypes of human rotavirus
6.   Transmission by faeco-oral route
7.   The outer surface protein is type specific Ag( viral haemagglutinin)

Wednesday, February 20, 2013

Rabies virus

Properties of Rabies virus:

   1.            Rabies is a member of rhabdovirus family

   2.            Enveloped, RNA, single stranded virus

   3.            Bullet shaped, neurotropic virus

   4.            Attaches to the Ach receptor on the cell surface

   5.            Replicates in cytoplasm, killed by sunlight, heat or lipid solvent

   6.            If not treated, 100% mortality

   7.            Reservoir- Dogs, cats, bats, fox, raccoons, skunks, jackal, hyena, Mongoose

Structure of Rabies virus

Disease caused by Rabies virus:

Disease caused by Rabies virus is Rabies or Hydrophobia.

Structure and Characteristics of Polio virus:

   1.            Non-enveloped, RNA virus
   2.            Replicates in cytoplasm
   3.            Single, stranded, Icosahedral nucleocapsid
   4.            Acid and bile stable but no long term carrier state
   5.            Three serologic (antigenic) types  based on different antigenic determinants on the outer capsid protein
   6.            Release upon death of the cell
A child suffering from Poliomyelitis

Disease caused by Polio virus:

Disease cause by polio virus is poliomyelitis

Pathogenesis of Poliomyelitis:

          Transmission: faeco-oral route (by ingestion of contaminated food and drink)
          Host: Human
          Incubation period: 7-14 days
          Mechanism of pathogenesis:
                           1.            Polio virus enters into the body by faeco-oral route
                           2.            Replicate in the lymphoid tissue of the orophraynx and SI (Peyer’s patches)
                           3.            Spreads through blood stream to the CNS and also spreads retrograde along nerve axons
                           4.            Then replicates in the motor neurons located in the ant. Horn of the spinal cord
                           5.            Death of nerve cells
                           6.            Result: Paralysis of the muscle innervated by those neurons. Also affects the brain stem, leading to bulbar poliomyelitis (with respiratory paralysis) but rarely damage the cerebral cortex.

Tuesday, February 19, 2013

Chalazion (Meibomian cyst)

Chalazion is the chronic inflammation of Meibomian glands due to blockage of its ducts.
Pathologically Chalazion is a chronic lipogranulomatous inflammation. It is not a true cyst as it is not lined by epithelium, rather it is lined by granulation tissue.

Sunday, February 17, 2013

LASIK (Laser Assisted In Situ Keratomileusis) :

LASIK is a type of eye surgery done to correct refractive errors of the eye.

Friday, February 15, 2013

Orbital Neoplasm

Classification of Orbital Neoplasm:

A) Orbital Neoplasm In children:

1.      Hamartoma and choristoma

2.      Vascular:

a.       Capillary Haemangioma (most common vascular tumor in children)
b.      Lymphangioma

3.      Neural:

a.       Optic nerve glioma
b.      Neurofibroma

4.      Mesenchymal:

a.       Rhabdomyosarcoma ( most common primary orbital malignant tumor of children)

5.      Metastatic:

a.       Retinoblastoma
b.      Leukemia
c.       Neuroblastoma

What is Hamartoma?

Hamartoma means excessive growth of normal tissue in normal site.
Eg: Capillary haemangioma and lymphangioma