Case Presentation
A 68-year-old Caucasian man presented with a 6-month history of firm skin papules,
starting on his face then gradually moving caudally, progressing to his arms, trunk,
and legs (Figure 1). Many of his lesions were asymptomatic. However, a few of the
papules were pruritic. The itching was alleviated by topical steroids.
On physical exam, multiple yellow-brown to red firm papules and small nodules were
noted on the face, trunk, and proximal extremities. Dermoscopic examination demonstrated
orange-yellow color surrounded by an erythematous border with occasional linear branched
vessels (Figure 2).
Histopathologic evaluation of 4 of the lesions revealed spindle cells in the upper
dermis (Figure 3). All 4 specimens had similar findings. Immunohistochemical studies
showed positivity for CD163, as well as Factor XIIIa. There was no significant positivity
for CD34. Laboratory data revealed a hemoglobin A1C of 9.3% and triglycerides of 461
mg/dL. An ophthalmology consult was obtained and no ocular pathology was found. A
serum protein electrophoresis was negative. With this information, a diagnosis of
adult eruptive xanthogranulomas was made.
Discussion
A xanthogranuloma (XG) is a type of non-Langerhans cell histiocytosis that most commonly
presents in infancy and childhood; however, several cases have been described in adults.
Xanthogranulomas present as dome-shaped papules or nodules on the skin. The condition
typically presents with a solitary yellow to reddish-brown growth. However, several
cases have been described of eruptive XGs in adults, or adult xanthogranulomas (AXGs)
[1–3]. The differential diagnosis of XGs is extensive and is based on clinical appearance,
associated comorbidities, histology, and immunohistochemistry.
Given the patient’s elevated Hg A1C, eruptive xanthomas (EXs) were considered. In
addition to diabetes mellitus, EXs are associated with dramatically increased low-density
lipoprotein (LDL) levels and hypertriglyceridemia. Our patient had LDL levels around
100 at the time of biopsy. His triglycerides were only moderately elevated at 461
mg/dL, whereas serum triglyceride levels typically exceed 1500 to 2000 mg/dL in EX,
leading us to favor other diagnoses.
Two other diagnoses included in the differential are necrobiotic xanthogranulomas
(NXGs) and progressive nodular histiocytosis (PNH), both of which can mimic eruptive
AXG. To rule out NXGs, a serum protein electrophoresis was ordered and found to be
negative for monoclonal gammopathy. Additionally, while NXG can be seen on the trunk
and extremities, it is typically seen primarily in the periorbital region, and our
patient had papules over his trunk and extremities, in addition to his face. Histopathology
was also not consistent with NXG. Finally, NXG can have ocular involvement, which
we ruled out with an ophthalmologic examination. PNH was thought to be a less likely
diagnosis, given the clinical features that are usually seen with this disease, such
as facies leonina, and its progressive nature. Our patient has normal facies and to
date has not experienced progression of the disease, but will continue to be monitored.
Finally, generalized eruptive histiocytosis was also on the differential as a type
of symmetric papular eruption of the skin on the trunk and proximal extremities. However,
this diagnosis was less likely given the histopathologic findings. Our patient had
multiple foamy spindle-shaped histiocytes and Touton giant cells.
We favored the diagnosis of eruptive AXGs, described previously as the presence of
more than 5 yellowish papules and nodules over the body [2]. AXG usually occurs in
men, at a ratio of 1.6:1, and more than 90% of the time, the lesions are found on
the trunk, followed by the head and neck. It has been reported on the extremities,
albeit rarely. The demographic fits our patient well, and the biopsied specimen confirms
the diagnosis of AXG.
Because XG in adults is uncommon, the diagnosis might not be immediately obvious.
Dermoscopy can be employed to help differentiate it from other diagnoses on the differential,
such basal cell carcinoma or sebaceous hyperplasia [4]. On dermoscopy, XGs, particularly
the juvenile type, have been described as looking like a “setting sun” [5]. This orange-yellow
color is not typical of the yellow “popcorn” appearance of sebaceous hyperplasia.
The vessels in sebaceous hyperplasia also differ from XGs. Sebaceous hyperplasia has
crown vessels [4]. Furthermore, XGs may have what look like arborizing vessels, as
seen in basal cell skin cancer. However, XGs will have a more yellow-orange hue on
dermoscopy than one might find in a basal cell carcinoma (BCC) and may also have clouds
of pale yellow dispersed through the papule (Figure 1). In one study, 90.9% of confirmed
XGs had this “setting sun” finding [5]. If suspicion is still high for a BCC, look
for other findings of BCC such as leaf-like structures, blue-gray ovoid nests or globules,
spoke-wheel structures, shiny white areas, or ulceration.
Conclusions
Our case represents the somewhat rare diagnosis of AXG. The diagnosis was suspected
based on dermoscopy and clinical morphology and was confirmed by histopathology (and
laboratory ruled out other, similar diagnoses). XGs will usually resolve in children,
while only approximately half of adult XGs regress [1]. Our patient was treated with
shave removal of symptomatic XGs with good results; however, isotretinoin can also
be used, with possible recurrence of lesions with discontinuation. Currently, the
etiology of AXG in otherwise healthy adults is unclear. Dermoscopy can help with diagnosis
and will show a characteristic yellow-orange hue, called the “setting sun” sign, and
is sometimes accompanied by linear, branched vessels around the border (Figure 4).
This can be reassuring to both patients and physicians to help rule out skin carcinoma
in which the color is not yellow and vessels tend to arborize across the lesion. Finally,
while most cases of adult eruptive XGs are idiopathic, reports have linked them with
hematologic and rarely solid organ malignancy; therefore, close monitoring of patients
with eruptive AXGs is warranted [6].