BACKGROUND
Necrobiotic xanthogranuloma (NXG) is a rare, granulomatous
disorder of unknown etiology that often presents
as firm plaques and nodules with a yellow-brown to red coloration. First described by
Kossard and Winkelmann in 1980, lesions may have associated telangiectases and ultimately
ulcerate. Healing typically occurs with scarring.1 NXG is associated with an
underlying paraproteinemia in a majority of cases-usually of the IgG kappa type.2
Skin lesions often present in a periocular distribution, but have also been reported to occur
on other areas of the head and neck as well as the trunk and extremities.3-4 NXG has also been found
within skeletal muscle as well as various internal organs including the heart, lungs, brain,
oral mucosa, larynx, and reticuloendothelial
system.5-10
In addition to its hematologic associations, other systemic manifestations
may be observed in patients with NXG. Along with paraproteinemias and multiple
myeloma, NXG has also been reported to occur in association with other malignancies
including leukemias, lymphomas and mycosis fungoides.4,9
On biopsy, lesions of NXG are characterized by a granulomatous
infiltrate that usually involves the entire dermis and often extends into the subcutis. Broad
areas of degenerated collagen (necrobiosis) are surrounded by histiocytes arranged as palisades.
Cholesterol clefts, nodular collections of lymphocytes with or without plasma cells are also commonly found.3
We report a case of an isolated cutaneous lesion of NXG appearing
on the right upper extremity in a 78-year-old male who presented with no
other clinical signs or symptoms. Following biopsy of this lesion,
the subsequent systemic evaluation led to the discovery of a previously undiagnosed multiple myeloma.
CASE REPORT
Our patient is a 78-year-old male who initially presented with a violaceous, indurated papule on
his right upper arm that was completely asymptomatic (Figure 1). Biopsy of this lesion revealed
a palisading granulomatous dermatitis with extensive areas of degenerated collagen (Figures 2-3).
Special stains for fungal organisms, acid-fast bacilli and polarized material were negative.
These findings were felt to be most consistent with an atypical necrobiotic xanthogranuloma.
His past medical history was remarkable only for hyperlipidemia
that had been controlled with atorvastatin. He had no known history of diabetes mellitus or
impaired glucose tolerance.He was taking no other medications or supplements, prescription or over-the-counter.
Given that the initial biopsy raised concern for a possible paraneoplastic
phenomenon, additional laboratory studies were obtained including serum immunofixation that revealed a monoclonal IgG kappa immunoglobulin with an M-spike of 1.2 g/dL. The total serum IgG was elevated at 1,780 mg/dL (normal
639-1349 mg/dL). Serum IgM was slightly decreased at 51
