Abstract:

Intercellular epidermal deposition of IgG in a continuous net-like pattern is a well-described direct immunofluorescence (DIF) finding in pemphigus. Punctate or dot-like intercellular IgG deposition has also been rarely described, but remains underrecognized. A 65-year-old woman with a prior leiomyosarcoma presented with painful erythematous, crusted plaques on the scalp, chest and inframammary folds for 4 months, that were initially thought to represent irritated seborrheic keratoses and treated with liquid nitrogen. No blisters or mucosal lesions were identified. Skin biopsy from chest revealed an acantholytic dermatosis with suprabasilar clefting. DIF revealed immunoreactivity for IgG involving the lower third of the epidermis in a speckled/dot-like intercellular pattern without immunoreactivity for IgA, IgM, C3 or fibrin. Given the unusual DIF findings, a subsequent biopsy was submitted from inframammary skin and showed a similar punctate intercellular pattern involving both IgG and C3 in the lower third of the epidermis, and linear staining for C3 at the dermo-epidermal junction. A diagnosis of pemphigus, possibly paraneoplastic, was considered. To exclude false-positive or non-specific staining, ancillary tests were performed. ELISA assay was moderately positive for desmoglein 3, but negative for desmoglein 1. Indirect immunofluorescence (IIF) on monkey esophagus was positive for intercellular IgG4. Envoplakin antibodies and IIF on rat bladder mucosa were negative, arguing against paraneoplastic pemphigus. A diagnosis of pemphigus vulgaris/vegetans was made. The patient was treated with systemic prednisone and rituximab with significant improvement. We report the unusual punctate pattern of immunoreactivity in pemphigus. Recognition of this pattern is crucial to avoid misinterpretation and ensure prompt initiation of therapy for this potentially serious disease.

Financial Disclosure:
No current or relevant financial relationships exist.

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Thet Su Win, MD, PhD