KD was first described in China by Kim and Szeto in 1937, and the original description was made by Kimura et al. in Japan in 1948
1,4. KD is a rare, chronic inflammatory disorder characterized by tumors mainly in the head and neck region, enlarged lymph nodes, increased eosinophil counts, and high serum IgE levels
5,6. The disease is most prevalent in Asians, uncommon in Caucasians, and rare in Africans. It has been suggested that one common factor is Asian ancestry
3. To date, the etiology of KD remains unclear, though various mechanisms have been proposed. These include: an aberrant immune reaction to
C. albicans, parasites, an unknown antigenic stimulus, or localized trauma and clonal rearrangements
2,3. Studies have shown that KD is a Th2-mediated disorder with overexpression of interleukin (IL)-4, -5, and mRNAs by the peripheral blood mononuclear cells and lymph nodes
7. Type 1 hypersensitivity to some allergens has also been considered as a possible mechanism
6.
Although the disease can manifest at any age, most cases have been reported in the second and third decades of life
2,3. An earlier review of 194 cases in the Japanese literature revealed that slightly over one-third of the cases occurred in the second decade
7. In another case series of 54 Chinese patients, the mean age of the patients was 33.1 years
7. The site most frequently affected by KD was the head and neck region (70%)
8. Less commonly affected sites often include the groin (15%), extremities (12%), and trunk (3%); rare sites of involvement have included the kidneys, orbits, ears, spermatic cord, and median nerve
8. This case presented here has two unusual clinical features: the age of onset (five years old) and the location of the lesion (the buttock). The youngest age reported has been 15 months
9, and the buttocks region has never been reported as the location of the lesion.
KD is very similar to ALHE, but is no longer used synonymously. KD is a chronic, allergic inflammatory disease of unknown etiology, whereas ALHE is thought to be a benign vascular proliferative disorder of unknown origin
10. Regional lymphadenopathy, peripheral blood eosinophilia, and increased serum IgE levels are commonly seen in KD, but not in ALHE. The nephrotic syndrome due to various types of glomerulonephritis has been more frequently reported in association with KD
10. Yuen et al.
11 reported that renal involvement is seen in around 60% of cases of KD patients. Histopathologically, KD is characterized by the formation of multiple lymphoid follicles with germinal centers, many of which are infiltrated by eosinophils leading to folliculolysis
1,10,12. Eosinophilic infiltration is usually massive, with formation of eosinophilic abscesses
10,12. By contrast, in ALHE, the lymphoid infiltration is more diffuse and lymphoid follicles are only occasionally found. Eosinophilic infiltration is more variable
10, ranging from sparse to abundant, and eosinophilic abscesses are rare. A vascular component is important in distinguishing KD from ALHE; vascular proliferation of ALHE is more prominent than that of KD. In ALHE, thick-walled blood vessels are lined with hypertrophic, low-cuboidal to dome-shaped epitheloid or histiocytoid endothelial cells containing vacuolated eosinophilic cytoplasm with vesicular nuclei
10,12. By contrast, the blood vessels in KD show either flattened or low-cuboidal endothelial cells that do not exhibit the characteristics of the epithelioid or histiocytoid cells
10. A summary of the similarities and differences between KD and ALHE is presented in
10.
| Table 1Comparison of Kimura's disease (KD) and angiolymphoid hyperplasia with eosinophilia (ALHE)10 |
In addition, the clinical manifestations of the case presented here were similar to cutaneous pseudolymphoma caused by insect bites. However, the patient had no history suggesting an insect bite, which may have included a noticeable site of the bite and/or pruritus. Moreover, there was neither epidermal hyperplasia nor wedge-shaped dermal infiltration on the histopathological examination.
The treatment of choice is said to be surgical excision
13. Although many alternative treatments, including radiation, high-dose intralesional steroids, and vinblastine have been attempted with good response; however, the tumors usually recur after discontinuing treatment or surgery. Some investigators have reported satisfactory results with cyclosporine
7,14 and pentoxifylline
13.
The case reported here revealed atypical clinical features of KD. However, the laboratory testing and the histopathological evaluation were consistent with the diagnosis of KD, and not with ALHE, insect bites, or any other malignant neoplasm.