Differential Diagnosis for 47-year-old Female with Lumbar and Flank Rash
Single most likely diagnosis:
- Herpes Zoster (Shingles): The description of a painful/burning rash with small fluid-filled vesicles, localized to one area (right lumbar and flank), is highly suggestive of herpes zoster. The lack of improvement with creams and prednisone does not rule out this diagnosis, as antiviral medication is the primary treatment.
Other Likely diagnoses:
- Contact Dermatitis: Given the patient's attempt to treat the rash with various creams, it's possible that the rash is a result of an allergic or irritant contact dermatitis, although the presence of fluid-filled vesicles is less typical.
- Eczema (Atopic Dermatitis): Could present with itchy, vesicular lesions, but the localized nature and the description of pain/burning are less characteristic.
- Folliculitis: An inflammatory process involving the hair follicles, which can present with itchy, painful lesions, but typically not with the fluid-filled vesicles described.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
- Necrotizing Fasciitis: Although rare and less likely given the description, any rapidly progressing, painful skin lesion, especially with systemic symptoms (not mentioned but important to consider), warrants consideration of necrotizing fasciitis due to its high mortality rate.
- Cellulitis with Abscess: While less likely given the vesicular nature, a severe bacterial infection could present with pain, redness, and swelling, and could potentially lead to sepsis if not properly treated.
Rare diagnoses:
- Pemphigus Vulgaris: An autoimmune disease that can cause blistering of the skin and mucous membranes, but it's rare and usually involves the mouth and other areas of the body.
- Bullous Pemphigoid: Another autoimmune blistering disease, which can present with large blisters but is less common and typically seen in older adults.
- Dermatitis Herpetiformis: Characterized by intensely itchy, blistering skin, but the blisters are typically smaller and more widely distributed, associated with celiac disease.