Differential Diagnosis for Pustular Rash
- Single most likely diagnosis
- Psoriasis: Given the description of a pustular rash with different stages of healing, mostly nonpruritic, and present for more than 2 years, psoriasis is a strong candidate. Psoriasis can present in various forms, including pustular psoriasis, which is characterized by the presence of pustules. The chronic nature and the distribution on the abdomen and shoulder also support this diagnosis.
- Other Likely diagnoses
- Pustular dermatosis: This condition can present with sterile pustules and can be chronic. The absence of pruritus and the distribution of the rash could fit this diagnosis.
- Subcorneal pustular dermatosis: A rare condition but one that presents with pustules and can be chronic. It's less common than psoriasis but should be considered in the differential for a pustular rash.
- Impetigo herpetiformis: Although typically associated with pregnancy, it can present with pustular lesions. However, its association with systemic symptoms and the specific context of the patient (61-year-old male) makes it less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Sweets syndrome (Acute Febrile Neutrophilic Dermatosis): Although it usually presents with fever, leukocytosis, and tender erythematous skin lesions, atypical presentations can occur. It's crucial to consider due to its potential association with underlying malignancies or infections.
- Paraneoplastic pemphigus: A rare autoimmune disorder associated with underlying neoplasms. It can present with a variety of skin manifestations, including pustules. Given the potential for an underlying malignancy, it's a "do not miss" diagnosis.
- Rare diagnoses
- Generalized pustular psoriasis: A rare and severe form of psoriasis that can present with widespread pustules. It's distinguished by its acute onset and systemic symptoms, which may not fully align with the chronic, nonpruritic presentation described.
- Acrodermatitis continua of Hallopeau: A rare form of pustular psoriasis that typically starts on the fingertips or toes but can spread. The description provided does not specifically mention acral involvement, making this a less likely but still possible rare diagnosis.
- IgA pemphigus: An autoimmune blistering disease that can present with pustules. It's rare and the clinical presentation can vary, making it a consideration in the differential diagnosis of a chronic pustular rash.