Discussion
For the first time, KD was described in 1937 in China; since then, only around 400 cases have been reported worldwide (10).
Classically, KD manifests with painless subcutaneous unilateral masses localized predominantly in the head and neck region (11). There are also several reported cases of subcutaneous masses in the groin, axilla, epicranium, oral cavity, nasal sinuses, auricle, orbit, eyelid, and inner canthus (12). In our case, the subcutaneous masses were located on both sides of the neck.
KD may be systemic and involve different organs, particularly kidneys (2). Renal involvement in KD is not uncommon (5), as approximately 10 to 60 percent of patients experience concomitant nephrotic syndrome (13) that might be concurrent with mass lesions onset or even months or years afterward (2). Renal involvement in KD may present as FSGS, membrane glomerulonephritis, diffuse proliferative glomerulonephritis, minimal change disease, and mesangial proliferative glomerulonephritis (14). In our case, FSGS was the result of renal involvement.
The pathophysiology of KD and its related renal involvement remains unknown (5). Previous studies have suggested that KD may be associated with endocrine disorders, infections, and autoimmune diseases that trigger the IgE-mediated type I hypersensitivity or induce a T-cell-mediated immune response, ultimately resulting in the deposition of eosinophils in involved tissue (13, 15). Moreover, genetics and sex hormones have been proposed to play a role in the pathogenesis of KD, as men are involved more than women (16).
KD may be misdiagnosed clinically and not differentiated from T cell lymphomas, Hodgkin’s lymphoma (28), uncommon infections, and sarcoidosis (8).
The diagnosis of KD is based on history and examination, laboratory findings, and histological studies (17).
The main histopathological findings of KD consist of increased eosinophils, follicular hyperplasia, and germinal centers containing IgE in obtained histologic specimens of the masses (7).
Additionally, the position and size of KD-induced masses can be determined by imaging studies, including computerized tomography, ultrasound, and magnetic resonance imaging which also makes surgical management easier (3). However, radiologic examinations have low specificity and may have similar findings with other benign and malignant conditions (3). Nevertheless, we are unable to make a definitive KD diagnosis until the excisional surgery and histological examinations of the masses have not been performed (18).
There is no unique standard therapeutic approach for the management of KD (6). The majority of patients with renal impairment properly respond to oral corticosteroid therapy (19), but the relapse of renal manifestations after corticosteroid therapy is not uncommon (20). In this regard, for some cases with relapse after the termination of corticosteroid therapy, corticosteroids combined with immunosuppressive therapy, such as cyclosporine and cyclophosphamide, have been recommended (21-23). Cyclosporine may play a critical role in the remission of KD by suppressing the activity of the T cell cytokines (24).
In addition to medical therapy, surgery, radiation, and chemotherapy have been recommended (5). In younger patients with localized lesions, surgical excision is typically the first-line choice for treatment and diagnostic purposes (25). Furthermore, nephrotic syndrome relapse might be suppressed with the early excision of the KD masses (26).
Radiation therapy has also been administered for patients who don’t respond to corticosteroid therapy. On the other hand, irradiation can decrease the risk of the long-term side effects of corticosteroids (27).
In our case, the renal involvement of KD responded well to prednisolone with no subsequent relapse.