A Case of Eruptive Collagenoma on the Left Calf: DISCUSSION part 2
The pathogenesis of eruptive collagenoma is unknown. Uitto et al showed that collagenoma almost exclusively consists of type I collagen and the underlying defect seemed to be a reduced production of collagenase in that location, and therefore a decreased local degradation of collagen. And some reports that the growth of collagenoma was influenced during pregnancy or puberty imply that hormone may be involved in the pathogenesis of this disorder.
No specific treatment is given in most cases. Two cases of eruptive collagenomas were reported to be treated with intralesional steroids with transient flattening of the lesions. Transient but exaggerated dermal atrophy after intralesional steroid injections may have resulted from the absence of elastic fibers in this disorder.
Clinically, our patient’s lesion could have been confused with sebaceus hyperplasia, xanthoma and collagen disorder. However, typical elastic fibers supported the diagnosis of collagenoma. In addition to its clinical features, the facts that it was acquired without a family history and associated disorders, were in favor of the diagnosis of eruptive collagenoma. Our case has a different characteristic from the previously reported cases. Nine cases, in the English literature and two cases in Korean literature have been reported to date. Most patients developed eruptive collagenoma mainly on the trunk, abdomen and upper extremities, whereas one patient developed lesions localized on the left back. To our knowledge, this is the first report of the eruptive collagenoma localized characteristically on the left calf. But the cause of distribution was not known.
In conclusion, we describe a case of eruptive collagenoma that occurred on the left calf, an area which is seldom affected in isolation.