Localized involutional lipoatrophy in a child.

Dear Editor:

Localized loss of adipose tissue without prior clinical or histologic inflammation is usually termed idiopathic lipoatrophy1. Localized involutional lipoatrophy (LIL), which was first described by Peters and Winkelmann2 in 1986, generally appears asymptomatic well-demarcated, depressed lesion on a single or in several sites3. Most of the reported cases occur in adolescence or in adulthood, but there has been only one reported childhood case of LIL2. Thus, we report a rare case of LIL in childhood in which triggering factors are not found and we reviewed the previously published reports.

A 5-year-old boy presented with an asymptomatic depressed lesion on his right buttock 1 month ago. The patient denied any history of injury or local injection at that site. He had no other medical problems or any associated drug intake. Physical examination revealed a well-demarcated, 3.0×3.5 cm sized hypopigmented, depressed atrophic patch (Fig. 1). Laboratory examination showed no abnormal findings in the patient's complete blood count, blood chemistry, C-reactive protein level, and autoantibody screening tests for antinuclear, anti-DNA, and anticentromere antibodies. Histopathological examination of a biopsy specimen showed epidermal atrophy and a decrease in the size of subcutaneous fat lobules composed of small adipocytes. There was no significant dermal or subcutaneous inflammation (Fig. 2). Immunohistochemical studies revealed CD68 positive macrophages within the fat lobules. We have followed up this patient without any treatments or procedures for 6 months, but there was no spontaneous regression.

Fig. 1

Well-demarcated, hypopigmented, and depressed atrophic patch on the right buttock.

Fig. 2

Histological examination of the skin biopsy specimen shows. (A) Epidermal atrophy, compaction of collagen bundle in the dermis without inflammation (H&E, ×40). (B) Diminutive fat lobules composed of variable sizes adipocytes (H&E, ×200). (C) Immature adipocytes resembling fetal fat tissue (H&E, ×400).

Peters and Winkelmann2 first reported LIL in 6 patients, most of all patients were adolescence or adult age except one 5-year-old boy. Yamamoto et al.3 reported 6 patients with LIL, all of whom were female, while 4 of the 6 patients had a history of local injections. Dahl et al.1 reported 16 patients with LIL, who had an average age of 32.8 year (range: 13 to 65 year) with female predominance; 9 of 16 patients had a history of antecedent intramuscular or intra-articular injections at the affected sites.

Histological examination presented variable sized fat lobules composed of small fat cells embedded in a well-vascularized and hyalinized background. Each adipocyte that resembles fetal fat tissue may vary in size, but are smaller than the normal fat cell3. LIL is also characterized by the presence of CD68-positive and mucin-positive macrophages scattered between the affected lipocytes. Lesional direct immunofluorescence findings are usually negative1,2.

The pathophysiology of LIL is still unknown. LIL is associatied with various immunologic disorders, which may suggest a background of immunologic dysregulation that may predispose for the development of LIL lesions after injection of medications such as antibiotics, insulin, or steroids1,3-5. Ultrastructurally, the activated macrophages were shown in close to fat cells. It is believed that these macrophages are activated after injury and secrete many cytokines, such as tumor necrosis factor-α, interleukin 1, platelet-derived growth factor, transforming growth factor-β1, and fibroblast growth factor-2, which may then mediate the involution of the adipose tissue5. In our case, we could not identified any triggering factors. However, we presumed that the cause of our case was any injury that included injection or trauma; most cases of childhood LIL were triggered after injection.

In conclusion, most reported cases have occurred in females of adolescent or adult age with a local injection history, but there has been only one report on childhood LIL2. Thus, we think that this case is very interesting in terms of age of onset, gender, and unidentified triggering factor.