Cutaneous pseudolymphoma (CPL) is an inflammatory condition described as a heterogeneous group of benign reactive T-cell or B-cell lymphoproliferative processes of diverse causes1. CPL has been associated with variable causes such as drugs, trauma, infections, inflammatory dermatoses, and reaction to foreign antigens introduced by arthropod bites, stings, infestation, tattoos, and vaccinations23. Although most cases are idiopathic, these associations suggest that CPL may be a reactive response to newly encountered antigens4. Here, we report a case of recurrent CPL derived from the rupture of multiple milia on the face.

A 72-year old woman presented with multiple confluent erythematous plaques on the forehead and left side of her face of 6-years duration (Fig. 1A). The patient had a medical history of hypertension although both clinical examination and blood test findings were otherwise unremarkable. She had no other symptoms such as fever, or history of recent travel, localised trauma, medication intake, or insect bites. Histologic examination of punch biopsy specimens taken from the plaques on her forehead revealed lymphoid nodules consisting of dense mixed lymphocytic infiltrates (Fig. 2A). Infiltrating cells were predominantly mixed with CD20 expressing cells and CD3 expressing cells (Supplementary Fig. 1A, B). The cells were focally positive for BCL2 and BCL6; CD43 was expressed only by T lymphocytes (Supplementary Fig. 1C~E). On the basis of the histological findings, a diagnosis of CPL was suggested. The patient was treated with oral prednisolone and topical steroids, and the lesions temporarily subsided. However, the lesions recurred, and upon closer examination, multiple milia were found within the lesions (Fig. 1B). Another biopsy was performed to capture the new lesions that included milia; histopathology showed dense lymphocytic infiltration recognizably derived from ruptured milia (Fig. 2B).

Based on the above findings, a new diagnosis of milium with pseudolymphoma was made. The lesions markedly subsided with oral prednisolone and intra-lesional triamcinolone injections. However, on subsequent follow-up, the lesions returned and were distributed around the site of recurrent milia. Thus, the milia were extracted, and the recurrence of CPL remarkably subsided. Subsequently, the symptoms were well-controlled with oral cyclosporine and intra-lesional injections of triamcinolone (Fig. 1C).

CPL has a wide range of presentations and histological features that may be misinterpreted clinically and histologically as cutaneous lymphomas.

In our case, the lesions were distributed within areas of milia; the histopathological findings of lymphocytic infiltrations along the ruptured milia suggested that CPL arose from the ruptured milia. In addition, by treating the milia, the CPL lesions improved and the recurrences were markedly reduced, which further indicated their association.

It was reported that persistent stimulation caused by nodular scabies, arthropod bites, and retained foreign materials can promote chronic antigenic reactions5. Similarly, keratin protein from the ruptured milia may act as an antigen that causes a persistent reaction, subsequently leading to the development of CPL.

To our knowledge, this is the first case report of CPL associated with milia although further studies are necessary. Spontaneous resolution of CPL may be induced by elimination of the underlying skin pathology which can be a persistent antigenic stimulus.