Localized Pseudoxanthoma Elasticum-like Changes on the Chin: DISCUSSION
PXE is a rare, genetic disorder primarily affecting the skin, eyes, and cardiovascular system. The inheritance is usually autosomal recessive, but may be autosomal dominant or sporadic. Cutaneous lesions usually occur in the second or third decade of life. However, the presence of cutaneous lesions is usually not noted until adolescence or even later adulthood because of the asymptomatic nature. The primary skin lesions are small, yellowish papules in a linear or reticular pattern, tending to gradually coalesce to form plaques giving the skin a “plucked chicken” appearance. A skin biopsy specimen is mandatory for the diagnosis of PXE to demonstrate the cardinal histologic features. PXE is characterized by degenerative changes affecting the elastic fibers of the mid-dermis. The elastic fibers are readily identifiable with hematoxylin and eosin (H&E) staining and are rather basophilic and irregular, appearing as widely dispersed granular material amidst normal collagen fibers. Fibers stain positively with the von Kossa technique, confirming the presence of calcium and phosphorous. In our case, there was no distinct skin finding, except the severe itching sensation localized to the chin of about 10 years duration. She did not have a family history of PXE. She was 60 years of age at that time of the skin biopsy, which showed PXE-like histologic changes, although she had unusual clinical features. Solar elastosis, which also exhibits abnormal elastic tissue, was easily excluded because in solar elastosis the material is located in the upper dermis and presents as dense masses rather than individual altered fibers. Moreover, these dense masses always stain negative for calcium.
Several types of localized PXE have been reported. According to Neldner and Martinez- Hernandez, localized acquired cutaneous PXE is a non-heritable form of PXE that is nearly identical to the heritable form on the basis of the cutaneous appearance of the individual lesions, light micro¬scopic criteria, and ultrastructural criteria. Localized acquired cutaneous PXE is distinguished from the more common syndrome by a late onset, absence of flexural clinical lesions, absence of retinopathy, a negative family history, and absence of the other expected systemic manifestations. In this report, different biochemical pathways are suggested; any condition that results in a sustained elevation of serum calcium and/or phosphate can result in cutaneous calcification that may or may not involve elastic tissue, and with specific regard to elastic tissue, different biochemical pathways can lead to the same outcome with calcified elastic fibers. Another localized form is localized acquired (periumbilical) perforating PXE. In most cases involving this type, the localized lesion occurs predominantly in middle-aged, multiparous, obese black women. Characteristically, it is an abdominal plaque located superior to the umbilicus. In consideration of the clinical manifestations, and personal or family history, our case might belong to the former type of localized PXE.
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