Definition: Bacillary angiomatosis is an infectious disease causing proliferation of small blood vessels in the skin and visceral organs of patients with human immunodeficiency virus infection and other immunocompromised hosts.
Etiology: It is caused by either Bartonella henselae or Bartonella quintana.  It is most often transmitted through a cat scratch or bite, though ticks, lice, and fleas may also act as a vector.  It can manifest in people with AIDS, and rarely appearing in those who are immunocompetent.
Clinical Features: Cutaneous BA is characterised by the presence of lesions on or under the skin. Appearing in numbers from one to hundreds, these lesions may take several forms:

    * papules or nodules which are red, globular and non-blanching, with a vascular appearance
    * purplish nodules sufficiently similar to Kaposi's sarcoma that a biopsy may be required to verify which of the two it is
    * a purplish lichenoid plaque
    * a subcutaneous nodule which may have ulceration, similar to a bacterial abscess

Clinical Approach: A blood test developed in 1992 by the CDC detects antibodies to the bacteria. It can be confirmed by reviewing symptoms, history and negative tests for other diseases that cause swollen lymph glands. It isn't necessary to biopsy a small sample of the lymph node unless there is a question of cancer of the lymph node or some other disease.
Treatment: While curable, it is potentially fatal if not treated.  BA responds dramatically to several antibiotics. Usually, erythromycin will cause the skin lesions to gradually fade away in the next four weeks, resulting in complete recovery. Doxycycline may also be used. However, if the infection does not respond to either of these, the medication is usually changed to tetracycline. If the infection is serious, then a bactericidal medication may be coupled with the antibiotics.

Eosinophilic folliculitis (EF)

Definition: Eosinophilic folliculitis  is an itchy rash with an unknown cause which is most common among individuals with HIV.  EF consists of itchy red bumps (papules) centered on hair follicles and typically found on the upper body, sparing the abdomen and legs. The name eosinophilic folliculitis refers to the predominant immune cells associated with the disease (eosinophils) and the involvement of the hair follicles.
Etiology: The cause of EF is unknown. A variety of microorganisms have been implicated, including the mite Demodex[6], the yeast Pityrosporum, and bacteria.  An autoimmune process has also been investigated.[
Clinical Features: Eosinophilic folliculitis typically appears as an area of erythematous papules and pustules. These involve the face in most (85%) affected patients.  Other locations include the back and the extensor surface of the upper extremities.  The papules gradually become confluent, creating indurate polycyclic plaques with a healing center and spreading periphery. They ultimately fade away, leaving residual hyperpigmentation and scaling.
Clinical Approach: Eosinophilic folliculitis may be suspected clinically when an individual with HIV exhibits the classic symptoms. The diagnosis can be supported by the finding of eosinophilia but a skin biopsy is necessary to establish it. Skin biopsies reveal lymphocytic and eosinophilic inflammation around the hair follicles.
Treatment: Treatment of eosinophilic folliculitis in people with HIV typically begins with the initiation of Highly Active Anti-Retroviral Therapy in order to help reconstitute the immune system. Direct treatment of the EF itself focuses on decreasing the inflammation and itching. Topical corticosteroids and oral antihistamines can alleviate the itching and decrease the size and number of lesions. Treatment with the antifungal drug itraconazole, the antibiotic metronidazole, and the anti-mite drug permethrin may lead to some improvement of symptoms. Other therapies include PUVA, topical tacrolimus, and isotretinoin.

Definition: Kaposi's sarcoma (KS) is a disease in which cancer cells are found in the tissues under the skin or mucous membranes that line the mouth, nose, and anus.
KS causes red or purple patches (lesions) on the skin and/or mucous membranes and spreads to other organs in the body, such as the lungs, liver, or intestinal tract.
Etiology: The epidemic KS, occurring as a disease that accompanies AIDS, is thought to have a cause - the virus named HIV (Human Immunodeficiency Virus). If given a blood test for HIV, nearly all patients with epidemic KS will show evidence of being infected.
Clinical Features: Kaposi's sarcoma consists of characteristic skin lesions that range from flat to raised purple plaques. These tumors have a rich network of small blood vessels, and red blood cells moving slowly through these channels lose their oxygen, changing from red to blue. The mixture of red and blue cells gives the KS lesion a characteristic purple color.
Clinical Approach: Doctors usually recognize Kaposi's sarcoma by its appearance. A biopsy is usually performed to confirm the diagnosis.
Treatment: Advanced therapies such as Moh's surgery and cryotherapy (freezing) are used to treat the symptoms of Kaposi sarcoma. Antiretroviral therapy, surgical excision, chemotherapy and radiation are also available.

Definition: Molluscum contagiosum is a relatively common viral infection of the skin that most often affects children. It results in firm bumps (papules) that are painless and usually disappear within a year without treatment. If the papules are scratched or injured, the infection can spread to surrounding skin.
Etiology: This virus spreads easily through direct skin-to-skin contact and through contact with contaminated objects, such as toys, doorknobs and faucet handles. The virus also spreads through sexual contact with an affected partner. Scratching or rubbing the papules spreads the virus to nearby skin, as can shaving.
Etiology: This virus spreads easily through direct skin-to-skin contact and through contact with contaminated objects, such as toys, doorknobs and faucet handles. The virus also spreads through sexual contact with an affected partner. Scratching or rubbing the papules spreads the virus to nearby skin, as can shaving.
Clinical Features:  Molluscum contagiosum results in raised, round, flesh-colored bumps (papules) on the skin. The papules:

    * Are small — typically about 1/16 inch to 3/16 inch (about 2 to 5 millimeters) in diameter
    * Characteristically have a small indentation or dot at their top
    * Can become red and inflamed
    * Can be easily removed by scratching or rubbing them, but this spreads the virus to adjacent skin

Clinical Approach: Generally, diagnosis is made on clinical grounds based on appearance of the lesions. Identification of characteristic intracytoplasmic inclusion bodies in histologic or cytologic preparations is made by hematoxylin and eosin (H&E) staining of biopsy sections.
Treatment: Because molluscum spreads easily, doctors often recommend medical treatment, especially for adults. Treatment for molluscum contagiosum may include removal of the papules by:

    * Scraping or curettage
    * Freezing (cryotherapy)
    * Laser therapy

Definition: Seborrheic dermatitis is a common skin disorder that mainly affects the scalp, causing scaly, itchy, red skin and stubborn dandruff. In addition to the scalp, seborrheic dermatitis can also affect the face, upper chest, back and other oily areas of the body.
Etiology: Though the exact cause of seborrheic dermatitis isn't known, several contributing factors seem to play a role, including an abnormality of the oil glands and hair follicles. People with this disorder seem to have increased oil (sebum) production.
Clinical Features: Common signs and symptoms of seborrheic dermatitis include:

    * Patchy scaling or thick crusts on the scalp
    * Yellow or white scales that may attach to the hair shaft
    * Red, greasy skin covered with flaky white or yellow scales
    * Small, reddish-brown bumps
    * Itching or soreness
    * Skin flakes or dandruff

Clinical Approach: Your doctor may diagnose seborrheic dermatitis after talking to you about your symptoms and examining your skin and scalp. Sometimes, a skin biopsy or other tests are necessary to confirm the diagnosis and to rule out other types of dermatitis.
Treatment: There's no cure for seborrheic dermatitis, but treatments can control its signs and symptoms. Treatment depends on your skin type, the severity of your condition and where it appears on your body.  Seborrheic dermatitis of the scalp are treated with antifungal medicated shampoos along with topical steroids in solution. Treatment of the face consists of topical antifungals and topical steroids.