Mastitis overview

# Overview
Mastitis is the inflammation of the breast. Mastitis commonly affects breastfeeding mothers. This is referred to as puerperal mastitis. Non-puerperal mastitis occurs in non-breastfeeding mothers. Mastitis rarely occurs in men. Inflammatory breast cancer has symptoms very similar to mastitis and so appropriate history and investigation is needed to rule it out.
The use of the term mastitis varies by geographic region.  In the United States the term mastitis usually refers to puerperal (referrring to breastfeeding mothers) mastitis with symptoms of systemic infection whereas outside the U.S. it is commonly used for puerperal and non-puerperal cases.  The term chronic cystic mastitis, also called fibrocystic disease, is characterized by noncancerous lumps in the breast.

# Historical Perspective
Mastitis was first described by Dr. G. Ranney of Michigan in a paper read before the Section of Obstetrics Medicine at the Brighton meeting of the British Medical Association and in 1887 Dr. Charles J. Wright documented its treatment in the British Medical Journal.  From the 1930s to the 1960s an epidemic form of puerperal  mastitis occurred frequently in hospital nurseries in industrialized countries.  During this period, hospital deliveries became more frequent, breastfeeding was not promoted, and the antibiotic era was only just beginning.  The dominant role of Staphylococcal infections and transmission between nursery personnel, infants and mothers was repeatedly demonstrated.  Epidemic mastitis has been regarded as a hospital acquired disease caused by highly virulent strains of penicillin-resistant Staphylococcus aureus.

# Classification
Mastitis can be classified according to several subtypes based on the etiology, the duration of the disease, anatomical location, immunological association and age of the patient.  Examples of this classification include puerperal or non-puerperal mastitis, chronic or acute mastitis, periductal or ductal, autoimmune or non-autoimmune (e.g. granulomatous and lupus mastitis) and pre-pubertal mastitis.

# Pathophysiology
Most clinically significant cases of non-puerperal mastitis start as inflammation of the ductal and lobular system and possibly the immediate surrounding tissue. Development of non-puerperal mastitis is the result of secretory stasis whereas puerperal mastitis occurs when bacteria, often from the patient's skin or the baby's mouth/nostrils, enters a milk duct through a crack in the nipple.

# Causes
Mastitis is caused by bacteria, mostly Staphylococcus aureus normally found on the skin, as well as Staphylococcus epidermidis, Streptococcus, E. coli, and Mycoplasma.  Mastitis can also be caused by fungi, most commonly Candida, that may be found in the oral cavity of the baby.

# Differentiating Mastitis overview from Other Diseases
Mastitis must be differentiated from other diseases that cause breast pain and/or swelling, such as galactocele, breast engorgement, mastodynia, fibrocystic breast disease, breast cancer, fibroadenoma, mondor's disease and breast trauma.

# Epidemiology and Demographics
Worldwide, the prevalence of mastitis ranges from a low of 1,000 per 100,000 persons, to a high of 10,000 per 100,000 persons, with an average prevalence of 4,700 per 100,000 persons.  Worldwide, the incidence of puerperal mastitis ranges from a low of 2,900 per 100,000 persons, to a high of 9,500 per 100,000 persons, with an average incidence of 6,200 per 100,000 deliveries within the first seven weeks after delivery.  Out of this, the incidence of those with mastitis needing hospitalization is 93 per 100,000 persons..  The percentage of those with mastitis who develop a breast abscess varies from 3% to 11%.  Mastitis commonly affects breastfeeding mothers between the ages of 21 to 35 years, with the highest occurrence in those between the ages of 30 to 34 years, even  when  parity  and  full-time  employment are controlled.  However, there is no difference between mastitis and breast abscess groups regarding age.  Women are more commonly affected with mastitis than men.  There is no racial predilection to mastitis.  Geographically the incidence of mastitis is higher in developing countries.

# Risk Factors
Mastitis usually occurs in women who are breastfeeding.  Women who are breastfeeding are at risk for developing mastitis, especially if they have sore or cracked nipples or have had mastitis previously.  Also, the chances of getting mastitis increases if women use only one position to breastfeed or wear a tight-fitting bra, which may restrict milk flow.  Mastitis that is not related to breastfeeding might be a rare form of breast cancer.  Women with diabetes, chronic illness, AIDS, or an impaired immune system may be more susceptible to the development of mastitis.

# Screening
According to the World Health Organization, there is no screening modality available for mastitis.

# Natural History, Complications, and Prognosis
If left untreated, up to 11% of patients with puerperal mastitis may progress to develop a breast abscess.  Complications that may arise from mastitis include: recurrence, milk stasis and abscess formation.  The prognosis is usually good and mastitis clears quickly with antibiotic therapy.  73% of smokers diagnosed with mastitis have the worst prognosis, especially those with non-puerperal mastitis, and have a higher rate of recurrence of breast abscesses.

# Diagnosis
The diagnosis of mastitis is mostly clinical.  In most cases, patients may present a few days after delivery with localized breast complaints.  The affected area is often close to the nipple and areola and commonly occurs on the upper inner side of the breast.  The affected area usually occurs only on one breast and very rarely is the whole breast affected.

## History and Symptoms
In most cases, patients may present a few days after delivery with localized breast complaints.  The affected area is often close to the nipple and areola and commonly occurs on the upper inner side of the breast.  The affected area usually occurs only on one breast and very rarely is the whole breast affected.
The most common symptoms of mastitis include: redness of the affected area, pain local to the affected area and local differential warmth.  Some patients may also experience flu-like symptoms, such as aches, shivering, and chills, although this is less common.

## Physical Examination
Common physical examination findings of mastitis include low to high grade fever, breast tenderness, and swelling.

## Laboratory Findings
Some patients with mastitis have a positive bacterial culture of breast milk.  Culture is rarely used to confirm bacterial infection of the milk because positive cultures can result from normal bacterial colonization, and negative cultures do not rule out mastitis.  Culture has been recommended when the infection is severe, unusual, or hospital acquired, or if it fails to respond to two days' treatment with appropriate antibiotics.  Complete blood count may show an elevated neutrophil count, though this is not specific to mastitis.

## Electrocardiogram
There are no characteristic ECG findings of mastitis, however, mastitis has been reported to unmask Type 1 Brugada Syndrome in which the ECG finding resolved when mastitis resolved.

## X-RAY
There is no significant finding diagnostic of mastitis on x-ray, although x-ray irradiation therapy in treating mastitis has been tried with success.

## CT SCAN
There are no CT scan findings diagnostic of mastitis. CT scan is helpful only when there is suspicious metastatic inflammatory breast disease.

## MRI
On contrast-enhanced MRI, most non-puerperal mastitis are characterized by non-mass-like lesions with heterogeneous signal intensity.  The observation of rim or rim-like enhancement on contrast-enhanced MRI with central hypointensity areas showing as hyperintensity on T2-weighted imaging is suggestive of the possibility of non-puerperal mastitis.
On MRI, most patients with granulomatous mastitis are characterized by segmental T2 hyperintensity with contrast-enhancement on T1, however, enhancing T2 hypointense mass with irregular margin was present in minority of patients with granulomatous mastitis.  Among the available radiological modalities, MRI is the most specific in the diagnosis of mastitis.

## Ultrasound
On ultrasound mastitis may show edema of the fatty tissue, hypoechoic areas in the breast tissue, dilated ducts, fluid collections or irregular hypoechoic masses suspicious for malignancy or hypoechoic mass-like lesions.

## Other Imaging Findings
On mammography, bacterial (puerperal or non-puerperal) mastitis usually shows ill-defined regions of increased density and skin thickening as shown below:
Mammogram of Mastitis

# Treatment

## Medical Therapy
Supportive care is the mainstay of therapy for puerperal mastitis.  Supportive therapy includes massage, heat application, cold compresses and frequent breastfeeding.  The treatment for non-puerperal mastitis is based on the underlying condition.  Pharmacological therapies for non-puerperal mastitis include prolactin inhibiting agents, antimicrobial therapy, and nonsteroidal anti-inflammatory drugs (NSAIDs).  Granulomatous mastitis has been treated with some success by a combination of steroids and prolactin inhibiting medications.

## Surgery
Surgical intervention is usually not the first treatment option for patients with mastitis.  Surgery is usually reserved for complicated mastitis with abscess formation that needs to be drained and granulomatous mastitis that may need excision.

## Prevention
Effective measures for the primary prevention of mastitis include avoidance of the risk factors as well as adhering to the following:
- Early contact of infants with their mothers, and early start of breastfeeding usually within the first hour.
- Infants should stay in the same bed as their mother, or close to her in the same room.
- Breastfeeding mothers  should  receive  skilled  help  and  support for proper breastfeeding  technique, whether or not she has breastfed before, to ensure good attachment, effective suckling and efficient milk removal;
- Every mother should be encouraged to breastfeed on demand, whenever the infant shows signs of readiness to feed, such as opening the mouth and searching for the breast.
- Every mother should understand the importance of unrestricted and exclusive breastfeeding and of avoiding the use of supplementary feeds, bottles and pacifiers.
- Women should receive skilled help to maintain lactation if their infants are too small or weak to suckle effectively.
- When a mother is in hospital, she needs skilled help at the first feed and for as many of the subsequent feeds as necessary.
- When a mother is at home, she needs skilled help during the first day after delivery, several times  during  the  first  two  weeks,  and  subsequently  as  needed  until  she  is  breastfeeding effectively and confidently.