From the Guidelines
The exact cause of subcorneal pustular dermatosis (SPD) remains unknown, but it is considered an autoimmune disorder with several factors implicated in its development, including abnormal neutrophil function and activation, underlying conditions such as monoclonal gammopathies, and genetic factors. The development of SPD is complex and involves multiple factors. Some of the key factors include:
- Abnormal neutrophil function and activation, which leads to the characteristic sterile pustules forming beneath the stratum corneum layer of the epidermis
- Underlying conditions such as monoclonal gammopathies (particularly IgA type), multiple myeloma, and other hematologic disorders, which are associated with SPD in approximately 10-20% of cases 1
- Inflammatory bowel disease, rheumatoid arthritis, and other autoimmune conditions, which have been linked to SPD
- Certain medications, which may trigger or exacerbate the condition
- Abnormal cytokine production, particularly tumor necrosis factor-alpha (TNF-α) and interleukin-8 (IL-8), which plays a role in neutrophil recruitment and pustule formation
- Genetic factors, which may contribute to susceptibility, though no specific genetic markers have been consistently identified It is essential to note that while the study by 1 discusses pustular psoriasis, it does not directly address the causes of subcorneal pustular dermatosis. However, the information provided highlights the complexity of pustular dermatoses and the need for further research to understand the underlying causes of SPD. Given the potential associations with underlying systemic diseases, patients diagnosed with SPD should undergo appropriate screening for conditions such as monoclonal gammopathies, particularly IgA type, and other hematologic disorders.
From the Research
Causes of Subcorneal Pustular Dermatosis
The exact etiology of subcorneal pustular dermatosis remains unknown, but several associations have been reported:
- Monoclonal gammopathy of undetermined significance, as seen in a case report where a patient with subcorneal pustular dermatosis was found to have concurrent monoclonal gammopathy of undetermined significance 2
- Multiple myeloma, as mentioned in several studies 2, 3, 4
- IgA and IgG gammopathies, with cases reported of subcorneal pustular dermatosis in association with monoclonal IgA gammopathy 5, 4 and IgG monoclonal gammopathy of undetermined significance 2
- Autoimmune diseases, such as pyoderma gangrenosum 3
- SARS-CoV-2 infection, with a reported case of subcorneal pustular dermatosis occurring after SARS-CoV-2 infection, suggesting a possible trigger for the disease 3
Pathophysiology
The pathophysiology of subcorneal pustular dermatosis has yet to be clarified, but data from a case report suggest that a non-antibody-mediated mechanism may be operative in the disease 6