KD is a rare, benign, chronic inflammatory disorder of (principally) young Asian males; the male:female ratio is 3:1 [3–5]. However, cases have been reported worldwide at ages of 1 to 66 years [6]. KD is characterized by painless, firm, diffuse, single, or multiple subcutaneous masses 1 to 7 cm in diameter, principally in the head and/or neck (76%), particularly around the parotid gland and in the submandibular region. Although extremely rare, lesions have also been reported in the axillary and inguinal regions, the trunk, abdomen, chest wall, peripheral extremities, epiglottis, long bones, breasts, genitals, orbits, and ocular appendages [7, 8]. The overlying skin is usually not significantly affected. Sometimes, skin itching, pigmentation, thickening, local erosion, or even ulceration may be evident. Associated regional lymphadenopathy and salivary gland enlargement are common [9]. Systemic associations include nephrotic syndrome, eczema, asthma, sinusitis, tuberculosis, and Loeffler syndrome [10–12]. Typically, the kidneys and skin are affected; the incidence of renal pathology ranges from 10–60% [7, 13, 14].
In terms of laboratory findings, an elevated blood eosinophil count and a high level of serum total IgE are the most prominent features of KD. These parameters are crucial in terms of diagnosis, treatment, and prognosis. Imaging findings such as those from ultrasound (US), computed tomography (CT), and magnetic resonance (MR) are nonspecific but reveal the lesional morphologies and the anatomical distributions [8].
A definitive KD diagnosis requires histopathological examination. The prominent histopathological characteristics include follicular hyperplasia with active germinal centers and small vessel hyperplasia. The diffuse interfollicular infiltrates are rich in eosinophils, lymphocytes, plasma cells, and mast cells. Sometimes, several eosinophilic microabscesses and fibrosis are observed [9, 15]. Histologically, lymphocytic eosinophilic hyperplasia (ALHE) is similar to KD and commonly affects women in the third to fourth decade of life. However, it is characterized by vascular proliferation with many large epithelioid or histiocytoid endothelial cells; eosinophilic infiltration is rare. ALHE lesions are smaller than those of KD, more numerous, more superficial, more erythematous, and more likely to bleed when irritated. ALHE is rarely associated with systemic disease, the lymph nodes, or the salivary glands. Table 2 summarizes the unique features of KD and ALHE [16]. Based on the histopathological and clinical findings, a diagnosis of ALHE could be excluded in our present case. Other KD differential diagnoses include Hodgkin and non-Hodgkin lymphoma, allergic granulomatosis, Kikuchi disease, and Mikulicz disease [17].
Table 2
Comparison of Angiolymphoid Hyperplasia with Eosinophilia and Kimura Disease
| | ALHE | KD |
| Gender | Typically middle-aged females | Predominantly young adult Asian males |
| Symtoms | Pruritus, pain, pulsation | Asymptomatic |
| Lesion type and location | Small and superficial, with overlying erythema; head and neck region | Large, mainly subcutaneous; overlying skin normal; head and neck region; may involve regional lymp nodes and salivary glands |
| Lymphoid follicles | Uncommon | Prominent lymphoid follicles with germinal centers |
| Vascular proliferation | Prominent vascular proliferation with large epithelioid/ histiocytoid endothelial cells; evidence of underlying vascular malformation may be evident | Some stromal vascularity with unremarkable endothelial cells |
| Fibrosis | Absent or limited | Prominent |
| Serum IgE level | Normal | Increased |
| Nephropathy | Absent | Present in up to 20% of patients |
| Fitzpatrick’s Dermatology 9th Edition [16] |
The etiology of KD is unclear. The condition may be an allergic reaction caused by infection with Candida albicans, parasites, or viruses, or arthropod bites, or may be due to dysregulation of T cell responses in patients with endocrine disorders and/or autoimmune diseases. It could also stem from a Th2 immune response triggering deposition of eosinophils in diseased tissue [18],[19].
There is currently no standard KD treatment [9]. The primary treatments include surgical excision, systemic steroids, cytotoxic drugs, radiation therapy, and chemotherapy [18]. Intralesional injection of corticosteroids has afforded good results. The disease recurrence rate attains 40% [17]. KD is benign and self-limited; malignant transformation has not been recorded. However, several complications of KD have been reported, including cerebral artery, jugular vein, pulmonary, mesenteric, and multiple arterial embolisms in the extremities [8, 18].
The diagnosis of KD in our patient was based on the typical epidemiological features (age and race), the medical history, clinical features, blood tests, and histological findings. This case was accompanied by eczematous skin lesions but no renal dysfunction was detected.