Lipoatrophy semicircularis occurs relatively rarely and mainly in younger women. The typical clinic with symmetrical, half-limb, mostly asymptomatic depressions on the front of the thighs indicates the diagnosis. For a characteristic case such as the one presented, further diagnosis is unnecessary. A search should be made for a chronic microtrauma as a trigger.
Lipoatrophy semicircularis, a band-like depression on the ventral sides of the thighs caused by a circumscribed atrophy of the subcutaneous adipose tissue, was first described in this form by Gschwandtner and Münzberger in 1974 . Younger women are affected in the majority [3,6]. The etiology and pathogenesis are still unclear, although recurrent microtrauma due to pressure seems most plausible [2,3,6]. The disease is mainly perceived as cosmetically disturbing. In most cases, spontaneous regression of the changes occurs [3,5].
The 31-year-old female patient, an accountant, presented because of a dent formation on both thighs that had been noticed for half a year. She reported episodic pulling and dull pain especially in the area of the dent on the right thigh.
Family and self history were unremarkable. The patient could not recall any major trauma or injection to the thighs. Upon intensive questioning, she stated that the edge of her work desk was exactly the height of the thigh indentations. She would lean there more often when using her printer. She does not take any medications.
Approximately 0.5 cm deep band-like depressions of the skin are seen on both thighs on the extensor side, right > left. The covering skin appears unremarkable (Fig.1).
6 weeks after initial presentation, the tissue depressions regressed slightly after avoiding leaning on the desk.
Lipoatrophy semicircularis is an atrophy of subcutaneous adipose tissue and is characterized by band-like semicircular horizontal depressions on the anterior thighs . Approximately 70 case descriptions have been documented in the literature to date, suggesting a rare change. However, some authors consider the clinical picture to be far more common than reported [3,6].
Almost exclusively women are affected, mainly between the ages of 20 and 40 [2,3,6]. Usually, the approximately 2 – 4 cm wide indentations are found symmetrically on both ventral thighs, but unilateral changes also occur [1,5]. Sometimes, several parallel constrictions are found, encompassing half of the limb, therefore semicircular . The skin is lesionally unchanged, neither indurated nor discolored, and the underlying musculature and bone are not involved . The lesions are usually, but not consistently, asymptomatic and regress completely or at least mostly within 9 months to 4 years. Recurrence is possible [2,3].
Etiology and Pathogenesis
The question whether the disease is a sui generis change or only a similar response of the subcutis to different noxae is still unclear. However, in recent years the majority of authors favor the latter cause.
Minimal and repeated mechanical trauma and the resulting deterioration of blood flow in the affected areas are the most frequently cited explanations for the phenomenon [2,3, 5, 6]. The constant localization as well as the observed spontaneous remission after avoidance of the blamed trauma speak for this .
Repeated microtraumas due to pressure, e.g. at washbasins, pressure on the flexor sides of the thighs due to peripherally elevated chair seating surfaces and / or direct pressure by table edges on the anterior sides of the thighs [2,3,5,6] are the most frequently cited causes.
Several factors may account for the observed sex distribution. The subcutaneous adipose tissue of females is considered more susceptible to disturbance, and depressions are more easily seen in the thicker female subcutis. In addition, women would consult a physician more often for cosmetic reasons [2,3].
It is a clinical diagnosis. All laboratory examinations and investigations in the course of further diagnostics did not reveal any directional findings including radiographic, neurological and electromyographic procedures [3,6]. Thus, based on our previous experience with this clinical picture, we also deliberately refrained from further examinations in our patient.
The changes are limited to the subcutaneous adipose tissue. Apart from a partial or complete loss of substance of the subcutaneous adipose tissue and its replacement by new collagen and isolated resorptive giant cells in the deep subcutis, there are no specific histological changes. Gschwandtner and Münzberger refer to this pattern as chronic localized atrophic panniculitis . The histopathological pictures distinguished in other localized lipoatrophies, into inflammatory or involutional , are not found in lipoatrophia semcircularis .
Lipoatrophia semicircularis can be distinguished from lipoatrophia anularis, which was described for the first time in 1953, because of its extension, the similar localization on the thighs and the spontaneous tendency to regression .
The formation of lipoatrophia semicircularis without preceding swelling and discoloration of the skin, without induration and depigmentation distinguishes it from deep circumscriptenous scleroderma .
Subcutaneous injections with insulin or glucocorticoids sometimes result in isolated adipose tissue atrophies. In addition to the anamnesis, these are ruled out by the frequent involvement of the cutis, among other factors.
If a triggering repeated trauma can be elicited by intensive questioning, there is a high probability of spontaneous regression if the trauma is avoided .