In our patient, recurrent fever and lymphadenopathy were the predominant symptoms and findings over a prolonged period. Sarcoidosis with renal involvement was suspected initially, as it was consistent with the patient's medical history and no other likely diagnoses had been identified. After lengthy investigation, the patient was diagnosed with classic Kaposi's sarcoma with involvement of the skin and viscera (stomach). Immunosuppressive therapy can be a contributing factor in the development of Kaposi's sarcoma, but our patient first received treatment with cortisone after his disease picture was already established. Cortisone may nevertheless have contributed to the development of lesions of the skin and viscera (3). The patient was hospitalised with infections on numerous occasions over several years, but no signs of immune failure were ever detected. The renal biopsy was re-evaluated by a pathologist following the diagnosis of Kaposi's sarcoma, but the pathologist was unable to find typical histopathological signs consistent with this disease. It is not certain that Kaposi's sarcoma can account for the entire disease course in this patient, which also featured several serious infections and a diagnosis of interstitial nephritis of unknown origin. Some of these comorbid conditions are unlikely to be attributable to Kaposi's sarcoma, but nevertheless create a confusing picture that complicates diagnosis. Five years prior to the diagnosis, a lymph node biopsy from the axilla had been described as 'peculiar', but no clear conclusion had been reached. Upon re-evaluation, the biopsy turned out to be consistent with Kaposi's sarcoma. Perhaps the diagnosis could have been made earlier if this biopsy had been sent for a second opinion.
Kaposi's sarcoma is a multifocal, low-grade, vascular tumour that may involve the skin, mucosa and viscera (3). The disease was first described by the Austrian doctor Moritz Kaposi in 1872 in five case reports, in which he referred to the condition as 'idiopathic multiple pigmented sarcoma' (4, 5). In the case reports he described oedema and purplish nodules on the skin, mostly on the hands and feet. He also performed microscopy of skin biopsies, and described small round cells (spindle cells), small haemorrhagic areas with nodules, and pigmentation (haemosiderin). All five patients died within 2–3 years.
In 1994, herpesvirus-like DNA sequences were identified in patients with AIDS-associated Kaposi's sarcoma (6), and were named human herpesvirus 8 (HHV-8). HHV-8 is a member of the gamma herpesvirus family. Gamma herpesvirus causes tumours, lymphoproliferative disorders and lymphomas in humans and animals. HHV-8 is suspected to have spread to humans in Mediterranean countries from animals in Africa. Most primary HHV-8 infections are asymptomatic (3). The exact mode of virus transmission is unknown, but the virus can spread through sexual intercourse and is also found in saliva. Mother-to-child transmission of the virus has been demonstrated in Africa (7). HHV-8 is necessary but not sufficient for the development of Kaposi's sarcoma (3).
Disease development is dependent on contributing factors such as chronic inflammation and immunosuppression (8). HIV indirectly promotes HHV-8 viral replication by suppressing the immune system and through the production of cytokines. Kaposi's sarcoma is the most common tumour in patients with AIDS, but HIV alone cannot cause Kaposi's sarcoma (6).
The prevalence of HHV-8 varies greatly, from high endemic areas in sub-Saharan Africa (30–70 %) via intermediate prevalence in Mediterranean countries (5–20 %) to low prevalence in Northern Europe and Japan (<5 %) (3, 9). HHV-8 prevalence reflects the incidence of Kaposi's sarcoma in these countries. Only between three and nine cases of Kaposi's sarcoma have been reported annually to the Cancer Registry of Norway (2003–2012) (10).
Kaposi's sarcoma is divided into four types on the basis of epidemiology, underlying aetiology and clinical extent. There is extensive overlap between the different types, both in clinical symptoms and prognosis, but the more indolent cases feature mostly skin lesions, whereas the more aggressive forms more often involve the mucosa and viscera. Classic Kaposi's sarcoma occurs most frequently in older men of Eastern European or Mediterranean origin. Endemic Kaposi's sarcoma was the commonest form in Africa prior to the AIDS epidemic. In Uganda, Kaposi's sarcoma accounted for 3–9 % of all cases of cancer in 1971. AIDS-associated Kaposi's sarcoma has been the dominant form in Africa since the 1980s. AIDS-associated Kaposi's sarcoma has a more aggressive course than endemic Kaposi's sarcoma, but can be slowed or made to regress by effective HIV treatment. Iatrogenic Kaposi's sarcoma is seen in immunosuppressed patients who have received organ transplants, especially in ethnic groups vulnerable to classic Kaposi's sarcoma in Mediterranean countries (3). Our patient best fits into the category of classic Kaposi's sarcoma, mainly on the basis of his origins and the absence of HIV infection or iatrogenic immunosuppression.
Histopathological findings are identical in the four types, with the most typical histopathological finding being spindle cells. The disease progresses in three histological stages: the first is the 'patch stage' and is characterised by flat, macular lesions. The next stage is characterised by plaques, while the final, tumour stage, is characterised by nodular lesions. These histological changes can easily be overlooked (5).
Treatment of Kaposi's sarcoma varies depending on the clinical type and symptoms. In the absence of symptoms, treatment may be postponed. Relevant treatments are surgical excision, topical interferon alfa-2b, radiotherapy and systemic chemotherapy (5). Since there is no treatment that can eradicate HHV-8, it is debatable whether Kaposi's sarcoma can be cured (11). Kaposi's sarcoma limited to the skin normally responds well to chemotherapy, whereas nodular lesions are associated with shorter progression-free survival (12). There are few guidelines for treatment, and the disease course after various forms of treatment has mainly been described in retrospective, observational studies with diverse findings. After a median follow-up of 28 months, one study found that 55.5 % of patients showed disease progression, and 2.3 % had died from Kaposi's sarcoma (12). In another study, median progression-free survival was 11.7 months following systemic chemotherapy, while half of all patients had died by 28.5 months (13). An Italian study found that only 12.2 % of patients with Kaposi's sarcoma died from the condition. However, this was in a cohort of elderly patients (median age at death was 82 years for women and 85 years for men), and most died from cardiovascular disease (14).