What is Bacillary Angiomatosis?
Bacillary angiomatosis (BA) is a bacterial infection that primarily affects people with dysfunctional immune systems (immunocompromised) - such as those with HIV or some types of cancer. The disease is caused by the bacteria Bartonella henselae and Bartonella quintana.
Symptoms of Bacillary Angiomatosis
The primary presentation of BA is the appearance of multiple red (erythematous) vasoproliferative nodules on the skin. They are essentially growths of blood vessels.
These growths primarily occur on the skin, but can be also present in other parts of the body and organs, including soft tissues, bones, lymph nodes, liver and spleen.
Other symptoms can be non-specific, including a persistent fever, abdominal pain, swelling of the lymph nodes and night sweats. Additionally, pleural effusions (presence of fluid around the lungs) can occur, and if the lesions are present on the spleen may result in peliosis, which means presence of blood-filled cysts in the liver.
Diagnosis of Bacillary Angiomatosis
BA is diagnosed via a combination of clinical examination, histology, and blood testing. A biopsy of the nodule is usually taken, especially if the lesion presents on the skin. This is a simple procedure, where the area is numbed with local anaesthetic, and a part of the lesion, or the whole lesion is cut away and sent for histological analysis.
During the histological analysis, the tissue is cut into very thin pieces, stained with specialised dyes that allow for visualisation of certain molecules and features, and examined under the microscope.
The histological findings for the diagnosis of BA include a proliferation (growth) of blood vessels in the lesion, infiltrate of neutrophils (immune cells that fight bacterial infections), and presence of ampophilic (reacts to both acidic and basic stains) plaques - these are formed by aggregated bacilli.
Bacilli are types of rod-shaped bacteria, and these include the causative agents of BA. To confirm the presence of the bacilli a stain called Warthin-Starry stain is used.
If blood is taken, cultures are set up to confirm bacteremia - the presence of bacteria in blood. This involves taking blood and incubating it with or without air (aerobic or anaerobic) and observed under a microscope for presence of growing bacteria [1, 2, 3, 4, 5].
Treatment for Bacillary Angiomatosis
As bacillary angiomatosis is a bacterial infection, antibiotics are the gold standard of treatment. The first-line therapeutic is erythromycin, taken as a tablet four times daily for 2 weeks to a month. Other antibiotics, including doxycycline, azithromycin, and clarithromycin can also be considered.
The choice of the antibiotic depends on the severity of the infection, as well as the patient's health, and potential resistance of the growing bacteria to some types of antibiotic.
What is Kaposi Sarcoma?
Kaposi sarcoma (KS) is a subtype of sarcoma, a type of cancer that arises from the connective tissues of the body.
Kaposi Sarcoma develops by a malignant transformation (cell mutating and turning cancerous) of the cells that form the internal lining of the blood vessels.
KS is associated with infection by viruses, including the human herpesvirus 8 (also referred to as Kaposi's sarcoma-associated herpesvirus), or HIV [1, 2, 3, 4].
Signs and Symptoms of Kaposi's Sarcoma
KS manifests as growth of multiple vascular nodules on the skin and/or other parts of the body or organs. These lesions are red, purple or brown in colour, and are most common on the legs and feet, particularly ankles and soles [5]. However, they can occur anywhere, including the nose, mouth, genitals and anus, especially over time as the disease progresses [2, 3].
These lesions may be asymptomatic initially (don't cause symptoms), however can lead to problems as they progress, grow and multiply. For example, a growing lesion may restrict the flow of the lymphatics or blood in the legs, leading to swelling and pain.
If the lesions grow within the digestive system, the disease presents with abdominal pain, diarrhoea or gastrointestinal bleeding. Lesions in the lungs and respiratory system cause shortness of breath, and can also bleed [5].
Diagnosis of Kaposi Sarcoma
KS is diagnosed by a combination of a clinical examination, laboratory tests and diagnostic imaging. Blood tests for viruses such as herpesviruses and HIV are performed, and clinical examination of the skin and mucous membranes provides insight into the lesions.
Imaging techniques, such as computed tomography (CT) or magnetic resonance (MRI) is used to identify internal lesions. For a definitive diagnosis, biopsy of a lesion is needed, which is then examined under a microscope for characteristic features of KS, such as presence of transformed cells and vascular proliferation (growth of abnormal blood vessels) in the lesion.
Treatment for Kaposi Sarcoma
The treatment of KS is based on the extent of the disease. A very important therapeutical consideration is the state of the immune system of the patient, as well as the overall status.
For localised disease (when there is only one or a few lesions and the cancer has not metastasised), removal of the lesion is the primary treatment option. For this, approaches include:
- traditional surgery,
- cryotherapy (freezing the lesion with liquid nitrogen),
- electrosurgery (the lesion is "burned off" with an electrocautery device)
- laser removal.
Additionally, the lesion may be irradiated to either shrink the tumour or post-operatively to ensure that all cancerous cells are killed.
If the disease is more advanced and/or metastatic, systemic chemotherapy is needed. Traditional cytotoxic drugs are used, however, a type of drug called liposomal anthracyclines, including pegylated liposomal doxorubicin (PLD), has shown good results with fewer toxic side effects than conventional chemotherapy, and is used increasingly often.
Additionally, antiretroviral drugs may be used in patients with HIV-associated KS with the aim to suppress the HIV infection and improve the patient's immune system function.
Prognosis for Kaposi Sarcoma
The prognosis of KS varies depending on the patient's overall health, immune system functionality and the extent of the disease. Generally, patients with a well-functioning immune system and localised disease have a better prognosis than those with dysfunctional immune system, and/or metastatic disease.
What are the Differences?
Bacillary angiomatosis and Kaposi's sarcoma are both conditions that occur in patients with dysfunctional immune system, including those with a HIV infection. The two conditions can present in a similar manner, by appearance of red vascularised (containing blood vessels) lesions on the skin. However, the two diseases are fundamentally different in their causes, and consequently treatment and prognosis.
Bacillary angiomatosis is a bacterial infection, with the primary causative agents being Bartonella henselae and Bartonella quintana. Under the microscope, the bacteria can be seen in the lesions, which is the primary diagnostic sign for bacillary angiomatosis. As it is a bacterial infection, bacillary angiomatosis can be treated and cured with antibiotics, with erythromycin being the first-line treatment [1, 2, 3].
On the other hand, Kaposi's sarcoma is a type of cancer that arises from the cells lining the blood vessels. Under the microscope, there are no bacteria visible in a Kaposi's sarcoma lesion. Consequently, Kaposi's sarcoma cannot be treated with antibiotics, and the treatment pathway is similar to other cancers. For localised disease, removal of the lesions is the primary objective. Metastatic disease requires more intensive treatment, including systemic cytotoxic chemotherapy, with pegylated liposomal doxorubicin being one of the treatments of choice [1, 4, 5].