A Case of Atypical Granuloma Annulare Presenting As Palmoplantar Pustules

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Granuloma annulare (GA) is an inflammatory skin disease characterized by ring-shaped, skin-colored to erythematous papules or plaques. GA is clinically classified into localized, generalized, subcutaneous, perforating, and patch types. However, it occasionally shows non-typical patterns such as palmoplantar, blaschkolinear, pustular, and visceral types1. Here, we report a case of atypical GA with palmoplantar pustules, not reported to date.

A 69-year-old man presented with a 2-week history of multiple palmoplantar papulopustules. His medical and family history were unremarkable except for taking talniflumate, a non-steroidal anti-inflammatory drug, for 26 days due to wrist ligament injury. Physical examination revealed multiple skin-colored, hyperkeratotic, pustular papules with tenderness in the palmoplantar area (Fig. 1). Arthralgia in fingers and toes were noted. Laboratory results showed slight elevation of erythrocyte sedimentation rate (26 mm/h, normal <20 mm/h) and C-reactive protein (0.4 mg/dl, normal <0.3 mg/dl). Palmar lesion histologically showed focal loss of the epidermis and collagen degeneration surrounded by histiocytes and lymphocytes in the upper to middle dermis (Fig. 2A~C), and a subepidermal neutrophilic pustule (Fig. 2D). Alcian blue (pH 2.5) staining of the palmar tissue revealed mild interstitial mucin deposition (Fig. 2E). The plantar lesion displayed palisading granuloma similar to that seen in the palmar lesion (Fig. 2F~H). Thus, this case was diagnosed as GA with palmoplantar pustules. The patient was treated with oral methylprednisolone (4 mg/day) and methylprednisolone aceponate cream (twice daily). The symptom and lesions resolved after 2 weeks of this treatment. After that, instead of methylprednisolone, alitretinoin was administered as maintenance therapy for 4 weeks, and he remained in an improved state. We received the patient’s consent form about publishing all photographic materials.

Fig. 1
A few hyperkeratotic pustular papules ranging from 2 to 5 mm in size on the palm (A) and sole (B).

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Fig. 2
(A) A necrobiotic granuloma in the upper to middle dermis beneath the subepidermal pustule in the palmar tissue (H&E, palm, ×40). (B) Palisading granuloma surrounded by infiltration of inflammatory cells (H&E, palm, ×100). (C) Eosinophilic degenerated collagen with infiltration of lymphocytes and histiocytes (H&E, palm, ×400). (D) A dense infiltration of numerous neutrophils in the palmar subepidermal pustule (H&E, palm, ×400). (E) Mild interstitial deposition of dermal mucin around a granuloma in the palmar tissue (Alcian blue stain [pH 2.5], palm ×400). (F) A necrobiotic granuloma in the upper to deep dermis of a plantar lesion (H&E, sole, ×40). (G) Palisading granuloma with homogenously eosinophilic necrobiosis and peripherally infiltrated inflammatory cells (H&E, sole, ×100). (H) Eosinophilic degenerated collagens with infiltration of lymphocytes and histiocytes (H&E, sole, ×400).

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Although the dorsum of the hand or foot is commonly involved in GA, the palm or sole is rarely involved. A few cases with palmoplantar GA belonging to papular or patch type were previously reported2, 3. However, there were no previously reported palmoplantar GA cases with pustular lesions as in our patient.

Perforating GA (PGA) sometimes shows pseudo-pustules without neutrophilic infiltration that histologically correspond to the transepidermal extrusion of degenerated collagen. However, true-pustules can also develop in PGA infrequently, when numerous neutrophils leak out along with the transepidermally extruded necrobiotic materials4. Although neutrophilic pustule in the area of focal epidermal loss and granulomatous lesion beneath the pustule were observed in our case, Masson’s trichrome stain showed no evidence of transepidermal extrusion of collagen, failing to support the confirmed diagnosis of PGA.

Regardless of epidermal perforation, follicular pustules can be formed in GA. When granulomatous areas are located adjacent to the hair follicles, palisading inflammatory cells may involve the follicular wall, causing folliculitis or follicular pustules5. However, the skin lesions of our patient were confined to the palmoplantar area where was absent of hair follicles. Therefore, our patient’s subepidermal neutrophilic pustules were thought to be unrelated with hair follicles.

To the best of our knowledge, this is the first report of a case of GA with palmoplantar pustules. Considering that GA may have an atypical pattern, it is necessary to perform skin biopsies for clinically uncertain lesions to make an accurate diagnosis.