Immunoglobulin A (
IgA)
pemphigus, also known as intercellular
IgA dermatosis, is a rare autoimmune bullous disease presenting with
IgA anti-keratinocyte cell surface
autoantibodies. Concomitant
lymphoproliferative disorders have been reported in
IgA pemphigus, including
IgA monoclonal gammopathy of undetermined significance and
IgA type
multiple myeloma (MM). A 35-year-old Japanese woman with a 3-year history of pruritic papulovesicles on her lower legs and trunk was referred to our department. Histopathological examination revealed acantholytic
blisters, and results of both direct and indirect immunofluorescence were negative. Direct and indirect immunofluorescence were still negative 3 years and 7 months later. Approximately 7 years after her first visit, the patient was re-referred to us because of
disease exacerbation. Histopathological findings revealed subcorneal blistering with
acantholysis, in which neutrophil-dominant inflammatory cells were present. Indirect immunofluorescence was positive for
IgA on the epidermal cell surface and both
desmoglein (Dsg) 1/3 and (Dsc)
desmocollin 1-3
enzyme-linked
immunosorbent assays (ELISAs) for
IgA were positive. The histological findings and positive Dsc1
IgA ELISA led to the diagnosis of
subcorneal pustular dermatosis (SPD)-type
IgA pemphigus. Further examination revealed hyper-
IgA globulinemia, increased serum
IgA-κ
protein, and increased plasma cells in the bone marrow, enabling the diagnosis of
IgA type MM.
Daratumumab,
lenalidomide, and
dexamethasone (DLd)
therapy was effective for both the MM and the skin lesions, resulting in negative results on Dsg1/3 and Dsc1-3
IgA ELISAs. The association between
IgA pemphigus and
IgA type
multiple myeloma remains unclear, and only seven cases including the present case have been reported. Literature review revealed associations between SPD-type and
IgA κ chain in
IgA pemphigus and MM, and that in most cases the onset or diagnosis of MM was simultaneous or occurred after the diagnosis of
IgA pemphigus. Therefore, clinicians should be aware of the development of
multiple myeloma during the
clinical course of patients with SPD-type
IgA pemphigus.