Primary Cutaneous Plasmacytosis: Masquerading as Hidradenitis Suppurativa.

Isolated cutaneous plasmacytosis (CP) is a rare entity with few cases reported in world literature. CP masquerading as hidradenitis suppurativa like presentation is a unique case with some features differentiating it clinically from it which were further confirmed by histopathology and immunostaining. Our case showed hyperplasia of mature plasma cells and polyclonal hypergammaglobulinemia, immunostaining for CD138 positivity and kappa: lambda ratio more than 3:1. Extensive clinical and laboratory investigations failed to reveal any underlying pathology, presence of any underlying disease accompanying the hypergammaglobulinemia and/or plasma cell proliferation.

What was known?

Cutaneous plasmacytosis is a rare disorder with most cases being described from Japanese region. Most cases have been described as reddish-brown indurated plaques on trunk and abdomen.

Introduction

Cutaneous plasmacytosis (CP) is a very rare, recently described entity in world literature. There are < 60 cases reported worldwide, no case reported from India till date. We report a case of primary CP in an adult female with site predilection of apocrine gland-bearing areas which has not been described previously in world literature.

Case Report

A 46-year-old married female presented with asymptomatic, multiple, reddish-brown lesions in axillae, mammary area, lower abdomen, perineum, and upper inner thighs since last 2 years. They started as small pea-sized lesions with a gradual progression in size and number. On general examination, there was no hepatosplenomegaly or lymphadenopathy. Cutaneous examination revealed multiple well defined erythematous skin to brown colored succulent-looking papulo-plaque lesions in the above-mentioned sites ranging from 0.5 to 10 cm in diameter [Figure 1]. The lesions were seen in both areolar and periareolar regions bilaterally. The vulva showed mainly papular lesions with a predominance of plaques in medial thighs which had atrophy as well. The plaques revealed erythematous firm elevated borders with crusting and scarring at places. There were multiple discrete lesions present around the plaques. Initially, a presumptive clinical diagnosis of hidradenitis suppurativa (HS) was made observing the distribution areas, and she was put on antibiotics and topical benzoyl peroxide 5%, but the lesions did not show regression. After 2 weeks, she was put on oral isotretinoin 1 mg/kg for a period of further 2 weeks, but still there were no signs of regression in the lesions. Moreover, new lesions kept on emerging. Hence, a biopsy was performed, and it revealed acanthosis, parakeratosis, mature polyclonal plasma cells with small uniformly sized nuclei present up to the deep dermis and fibrosis [Figure 2]. Interestingly, the folliculosebaceous apparatus was seen to be uninvolved at places with plasma cell infiltrates in dermis, excluding the diagnosis of HS. The diagnosis was thus revised to CP.

Figure 1

(a-d) Multiple erythematous, red-brown infiltrated plaques distributed in apocrine gland bearing areas but not strictly bilateral. Well defined fibrosed plaques seen in upper medial thighs

Figure 2

(a) Perivascular and periadnexal patchy infiltrate of mature typical plasma cells admixed with some lymphocytes and histiocytes (H and E, ×10). (b) Kappa stain (immunostain, ×10). (c) Lambda stain (immunostain, ×10)

Immunohistochemical examination revealed a polyclonal staining pattern with kappa to lambda ratio of 3:1, with CD138 being positive [Figure 3]. Serum protein electrophoresis revealed polyclonality with levels of IgG as 2300 mg/dL (reference range 880–1800 mg/dL), IgA as 762 mg/dL (reference range 126–517 mg/dL), IgM as 486 mg/dL (reference range 52–270 mg/dL), and IgE as 980 mg/dL (reference range 0–450 mg/dL). Urine Bence-Jones protein was negative. Serological tests for HIV and syphilis were nonreactive. Antinuclear antibody was within normal limits. Interleukin 6 (IL-6) was not done. IgG4 was done, and it was negative. Chest X-ray, ultrasound whole abdomen and pelvis and computed tomography scan did not reveal any significant abnormality. Bone marrow examination revealed a normocellular marrow with normal myeloid to erythroid ratio and plasma cells being 4% of marrow cellularity. Since no internal organ was involved and also there was no history of any previous cutaneous disease, the final diagnosis was confirmed as primary CP.

Figure 3

(a) Sparing of hair follicle with perifollicular plasmacytic infiltrate (H and E, ×400). (b) CD138 positivity (immunostain, ×400). (c) Kappa positivity (immunostain, ×40). (d) Lambda positivity (immunostain, ×400)

She was put on prednisolone 40 mg/day and after 8 weeks of treatment, there was moderate effect in that there were no new lesions and size and elevation of old lesions regressed. We have currently put her on monthly follow-up to monitor progression to systemic Plasmacytosis (PC), and it has been 1 year now she has not developed systemic involvement.

Discussion

Cutaneous and systemic plasmacytosis (CSP) is a rare disorder with approximately 60 cases being reported worldwide, mostly from Japan; none from the Indian subcontinent. The cases of isolated CP are even less. It consists of a triad of cutaneous lesions, superficial lymphadenopathy, and polyclonal hypergammaglobulinemia.[12] It was first reported in 1976, with the first case in English literature being reported by Watanabe et al., in 1986.[3]

Cutaneous lesions are characterized by disseminated reddish-brown macules and plaques distributed mainly on the trunk. There may be systemic involvement with hepatosplenomegaly and constitutional symptoms, but the term systemic plasmacytosis is used in such cases. Extracutaneous involvement of lymph nodes,[4] lungs, liver and spleen is also seen.[3] Among all the systemic sites, superficial lymphadenopathy is the most common and is seen in approximately 70% of patients.[5]

Histologically, Uhara et al.[4] stated that the most characteristic histopathological change in CP is perivascular and periadnexal patchy infiltrate of mature typical plasma cells admixed with some lymphocytes and histiocytes. Immunohistochemistry is polyclonal IgG predominated.

Cutaneous plasma cell infiltration of the skin can be due to various reasons ranging from neoplasms to infections. The differential diagnoses to be considered are malignancies (cutaneous plasmacytoma, marginal zone B-cell lymphoma, follicle center B-cell lymphoma), systemic lupus erythematosus, scleroderma, infections (bacterial, fungal, mycobacterial, syphilis), plasma cell vulvitis, systemic plasmacytosis, nodular amyloidosis, and cutaneous Rosai–Dorfman disease. In this case, HS/Acne inversa (AI) is an additional diagnosis to be considered. Here, although significant fibrosis was present and the IgG4 levels were normal, we favor the diagnosis of CP because:

Absence of ruptured cysts, follicular involvement clinically in this patient, which characterize AI

In the vulval area, predominant areas involved were upper medial thighs and not vulva proper. There were erythematous succulent and fibrosed asymmetrical plaques in upper medial thighs, unlike the lesions of AI. Also, there was no predominant areolar area involvement

The infiltrate is predominantly non-specific lymphohistiocytic, plasma cells, mononuclear infiltrate, and neutrophilic granulocytes in AI, which is lacking here. No sinus tracts or late apocrine gland involvement was seen.

Basically, the inciting event leading to proliferation of plasma cells has been unknown till date. Some reports state[5] that infections may be a predisposing factor for such proliferation. Kodama et al.,[6] detected increase in serum IL-6 in systemic plasmacytosis and intralesional injection of corticosteroids has led to decrease in lesions in few patients.[7] We also are of the view that maceration and friction in these areas in predisposed individuals may lead to the development of CP in patients as seen in our patient.

Long-term prognosis of patients with benign plasma cell proliferation is good. Uhara et al.,[4] reported that serum immunoglobulin levels more than 5000 mg/dL as well as plasma cell counts in bone marrow more than 6.9% are associated with the more severe clinical course. Fatal outcomes are seen with CSP, where renal, T-cell lymphoma, or interstitial pneumonia have been the cause of death.

Regarding treatment options available for CP, psoralen and ultraviolet A, radiotherapy, systemic chemotherapy (cyclophosphamide, epirubicin, vincristine, and prednisone), intralesional steroids have all been tried with variable success rates.[78910] Recently, topical 5-aminolaevulinic acid photodynamic therapy using long-pulsed ruby laser has been described as a novel treatment option.[11]

Conclusion

We present the case due to its rarity and its unique distribution of lesions. Moreover, on a closer look, we can appreciate well- to ill-defined plaque lesions which partly involve areola but mainly the peri-areolar skin. Similarly, in vulval region, although the lesion distribution simulates HS, these types of lesions are different. Hence, a very meticulous observation of the lesions is very important as is very well highlighted in this case.

Whenever cases of CP are encountered, search for underlying diseases leading to plasma cell infiltration as well as systemic plasmacytosis is warranted.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

What is new?

We report the first case from Indian region with lesions of cutaneous plasmacytosis masquerading as hidradentis suppurativa, which has not been previously reported. They were further confirmed by immunostaining.