Acral Sclerosing Histiocytic Nodules: A New Entity in Cutaneous Histiocytosis?

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To the Editor:
The histiocytoses are a heterogeneous group of diseases characterized by accumulation of reactive or neoplastic histiocytes in various tissues. Here, we report a case of a recently described and less known non-Langerhans histiocytosis.
A middle-aged female presented with gradually progressive, asymptomatic nodules over hands and feet since past 2 years. On examination, 4 well-defined, skin-colored to erythematous, nodules of size 2–3 cm were noted on the palmar surface of the left hand, involving the proximal and the middle phalanges of the ring and the little finger (Fig. 1). The nodules were firm in consistency and were mobile in both horizontal and vertical planes; the skin over the nodule was shiny with loss of normal skin folds, and there was scaling at places (Fig. 1). Multiple small nodules of similar morphology were noted over bilateral feet. A punch skin biopsy was obtained from one of the nodules over the palm and submitted for histopathological examination (Figs. 2A, B).
Skin biopsy showed thinning of the epidermis with effacement of the rete ridges. Multiple sclerotic, nonnecrotizing, nodular granulomas palisaded by spindle-shaped macrophages and occasional giant cells were seen in the dermis and subcutis (Figs. 2A, B). There was no lipid or hemosiderin pigment or any cholesterol clefts. The vessels were normal and showed no evidence of vasculitis. On immunohistochemistry, these macrophages stained strongly for CD68 but S100 was negative. An excision biopsy was obtained, and the nodule was found to be free from the underlying tendons. The excision biopsy showed similar morphology on histopathology. There was no evidence of fungal or mycobacterial infection on tissue staining (periodic acid–Schiff and modified Ziehl–Neelsen stain), cultures, and polymerase chain reaction (for fungal and mycobacterial sequence) of both punch and excision biopsy specimens. X-ray of the hand showed soft tissue nodules and serology for rheumatoid factor and anticyclic citrullinated peptide was negative. Other hematological and biochemical investigations, including serum uric acid were within the normal range, and there were no features to suggest hemophagocytic lymphohistiocytosis. Chest x-ray and ultrasound abdomen did not reveal any abnormality. However, she was detected to be seropositive for HIV-1 antibodies with a CD4 cell count of 600 cells per microliter. At 6 months follow-up, the lesions are stationary and the patient has not developed any systemic features.
Our patient had unusual clinical and histological features. The differential diagnosis considered at presentation included calcinosis cutis, gout, rheumatoid nodule, fibroma of the tendon sheath (FTS), and giant cell tumor of the tendon sheath (GCTTS). Both FTS and GCTTS present as solitary subcutaneous nodules.1,2 Multiple and multifocal lesions as in our patient are usually not seen, although bilateral symmetrical GCTTS have been described.3 Furthermore, FTS and GCTTS have characteristic histopathology, fascicles of spindle-shaped benign cells embedded in a collagenous stroma, containing irregular slit-like vascular spaces in the former and sheets of round, mononuclear cells in a fibrotic collagenous matrix, with multinucleated giant cells, hemosiderin granules, and foamy macrophages in the later.1,2 None of these features were seen in our patient. Lack of joint pain, soft tissue nodules on x-ray, and negative rheumatoid factor made gout, calcinosis cutis and rheumatoid nodules an unlikely diagnosis, and was further excluded by histopathology.
Immune dysfunction due to viral infections is implicated in various histiocytoses, and HIV infection is known to be associated with Rosai–Dorfman disease and hemophagocytic lymphohistiocytosis.4,5 The significance of HIV infection in causing histiocytic nodules in our patient is not clear and needs further investigation.
Patel et al6 have reported a patient with similar clinical and histopathological features as in our case. Their patient also had multiple, bilateral, pale-yellow, firm nodules around the interphalangeal joints of the hands.
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