Question

pathophysiology of Cellulitis?

Answer 1

definition

Cellulitis is defined as the infection of the subcutaneous tissue and fat and the deeper dermis due to

[most commonly )bacterial infections such as staphylococcus aureus , beta hemolytic Streptococcus of group A .This generally occurs due to bacterial invasion following damage to the skin following a scratch, a bite or through a wound and in dermatoses with the bacteria entering the deeper layers of the dermis.

etiology.Cellulitis could be due to

1.Bacterial infection : staphylococcus aureus (MRSA STRAIN), beta hemolytic Streptococcus group A

2.chemical irritation as in intravenous drug or fluid extravasation

3.foreign body irritation as in new slippers or jewellery

4.skin dermatoses like psoriasis with damaged skin

5.chronic conditions which cause the skin edema like elephantiasis ,Milroys' disease, chronic renal failure chronic heart failure and cirrhosis of liver.

The predisposing conditions for cellulitis are

a) local skin damage with injury cut ,fracture or burn to skin

b)conditions with skin damage,chronic dermatoses

c)edema of the subcutaneous tissues persistent over a long period as in renal failure and congestive heart failure.

d)weakened immune system as in diabetes mellitus,patients on steroids and immunosuppressive drugs and other immunosuppressive conditions

e) obesity.

TYPES OF CELLULITIS

1. extremity cellulitis(most common)

2 facial cellulitis

3.periorbital and orbital cellulitis.

4. PerIneal cellulitis

5..Buccal cellulitis

Patho physiology of cellulitis:FLOW MAP OF CELLULITIS.

stimulus(bacteria,chemical,foreign body,dermatosis)causing skin damage------>invasion of deeper dermis and subcutaneous tissue----->release of inflammatory cytokines,chemokines, ,prostaglandins,leukotrienes-(swelling,pain,edema,warmth)--->body defense activation(recruitment of neutrophils,macrophages and mast cells)--------->phagocytosis and bacterial death(treatment with antibiotics,antiinflammatory drugs)------>resolution of signs and symptoms

Explanation:

1.Following the skin trauma, there is invasion of the bacteria into the subcutaneous tissue .

2.This causes inflammatory response from the local cells. macrophages mast cells which are present in the subcutaneous tissue. There is release of inflammatory cytokines like interleukin-6, interleukin 1, beta tumor necrosis factor alpha and interleukin 15 ,leukotrienes, histamine and prostaglandins..

3.This  causes an acute inflammatory reaction with local vasodilation and WBC infiltration.

4.There is an inflammatory response by the neutrophils and the macrophages to engulf the bacteria, prevent it from spreading into deeper tissues and protect the body from infection.

5.These inflammatory cytokines are responsible for the swelling ,redness,warmth, the pain, fever that is associated with the cellulitis.

6.The body defenses along with the antibiotics and anti inflammatory drugs help in the resolution of the infections

7.Sometimes the infection (bacterial invasion)can spread into the bloodstream and cause widespread septicemia.

Pathophysiology of special forms briefly explained:

Facial cellulitis can occur from infected lymph node or an infected dental abscess. it can spread to the face eventually if infection is not controlled, The treatment a is aimed at identifying the underlying cause  first and giving broad spectrum antibiotics with an anerobic cover especially in case of dental abscess.

Buccal cellulitis is a condition which occurs generally in young children who are less than 12 months of age and have cellulitis on the cheek due to skin infection and generally spreads very fast causing widespread bacteraemia .

Perineal cellulitis generally occurs from the infection of the skin and the hair follicles in the perineal  area This is generally poly microbial containing mixed aerobic and gram-negative organisms and a broad-spectrum antibiotic with gram negative cover must be started in case of perineal cellulitis.

Periorbital cellulitis is an extremely serious condition and emergency of the highest nature. It occurs following injury to the skin of the eye or the eyelid. and invasion by staphylococcus or b -hemolytic streptococus. There is an agressive infection which goes down deep into the periorbital tissues and can reach the brain. It can cause vision loss and even spread to the brain causing meningitis,brain abscess. cavernous sinus thrombosis .It  is a serious condition and should be treated with utmost emergency

Complications of cellulitis

The common complications of cellulitis include spreading infection,abscess,pus formation,local gangrene .systemic bacteremia, widespread septicemia and multiorgan failure .

Specific complications are seen in case of facial cellulitis perineal cellulitis and periorbital cellulitis as discussed above.

Treatment: Understanding the pathophysiology of the cellulitis is the most important part in the treatment of cellulitis .

Since there is a series of inflammatory responses due to bacterial infection as the cause, the treatment options are directed towards resolving the infection and the inflammation and controlling them.

1.Antibiotics as per bacterial culture and drug sensitivity(especially in cases of MRSA with standard isolation precautions)

2.anti inflammatory drugs and antipyretics.

3.removal of the irritant in cases of chemical or foreign body induced cellulitis

.4 local application of glycerine magnesiumsulfate solution to decrease the edema

5. limb elevation

6. treatment of a specific cause in special cases

7.correction  of condition such as anaemia,uncontrolled blood sugars,improving general immunity,multivitamins especially vitamin c.(wound healing vitamin)

Recurring cellulitis pathophysiology:

Cellulitis has a chance of recurrence in the percentages of 8 to 20 if the underlying  factors which are causing it are not corrected. hence attempt should be made to correct the underlying factors of the cellulitis once the acute episode has settled.Treatment aimed at the control of predisposing factors help in control of recurring cellulitis.

Summary:

To summarise.Cellulitis is an inflammatory condition of acute nature of the subcutaneous tissues and fat and the deeper dermis caused by invasion of bacteria ,most commonly,beta hemolytic Streptococcus group A. staphylococcus aureus , there by inciting a series of inflammatory responses causing local swelling, pain, warmth and the treatment is directed towards treating the cause with use of antibiotics anti inflammatory drugs and general immunity improvement measures.