Mast cell distribution, activation, and phenotype in xanthoma

Possible roles of human mast cells in the formation of xanthelasma palpebrarum

Cutaneous xanthoma consist of foam cells that originate from monocytes or macrophages and accumulate in perivascular areas of the skin. The main component of these cells is oxidized low-density lipoprotein (oxLDL). In this study, we show that mast cells surround the accumulated foam cells, suggesting their involvement in xanthoma formation. Coculture of THP-1 or U937 monocytes with the human mast cell line LUVA upregulated their uptake of oxLDL. Positive staining for intracellular cell adhesion molecule-1 (ICAM-1) at the borders between mast cells and foam cells was seen in pathological specimens of the most common cutaneous xanthoma, xanthelasma palpebrarum, and in cocultures. In the latter, ICAM1 messenger RNA levels were upregulated. The administration of anti-ICAM-1 blocking antibody inhibited the increase in oxLDL uptake by THP-1 or U937 monocytes cocultured with LUVA. Taken together, these results suggest a role for mast cells in the formation of xanthelasma palpebrarum and the involvement of ICAM-1 in this process.

Mast Cells in Human Cutaneous Neurofibromas: Density, Subtypes, and Association with Clinical Features in Neurofibromatosis 1

BACKGROUND

Cutaneous neurofibromas (cNFs) are hallmarks of neurofibromatosis 1 (NF1) and cause the main disease burden in adults with NF1. Mast cells are a known component of cNFs. However, no comprehensive characterization of mast cells in cNFs is available, and their contributions to cNF growth and symptoms such as itch are not known.

METHODS

We collected 60 cNFs from ten individuals with NF1, studied their mast cell proteinase content, and compared the mast cell numbers to selected clinical features of the tumors and patients. The tumors were immunolabeled for the mast cell markers CD117, tryptase, and chymase, and the percentage of immunopositive cells was determined using computer-assisted methods.

RESULTS

The median proportions of positive cells were 5.5% (range 0.1-14.4) for CD117, 4.0% (1.2-7.0) for tryptase, and 5.0% (1.1-15.9) for chymase. The median densities of cells immunopositive for CD117, tryptase, and chymase were 280, 243, and 250 cells/mm2, respectively. Small tumors, growing tumors, and tumors from patients below the median age of 33 years displayed a high proportion of mast cells. Cells expressing both tryptase and chymase were the predominant mast cell type in cNFs, followed by cells expressing chymase only.

CONCLUSION

The results highlight the abundance of mast cells in cNFs and that their number and subtypes clearly differ from those previously reported in unaffected skin.

Xanthelasma Palpebrarum: More than Meets the Eye

Xanthelasma palpebrarum (XP) is the most common form of cutaneous xanthomata, and is important aesthetically, because of its close relation to the eyes, as well as medically for its association with cardiovascular disease (CVD). To provide avant-garde review discussing the various aspects of XP, including its aetio-pathogenesis and various treatment modalities. A structured Pubmed and Medline were searched for relevant articles. The finding of recent research has strongly espoused the link between XP and CVD, and mechanisms have been suggested for its formation. The new technologies have led to a multitude of treatment options for XP. XP is a multi-faceted entity; other than simple treatment of the cosmetic aspect of the disease, one must be cognizant of its cardiovascular implications.