Differential Diagnosis for Lower Back Pain and Blister in Inner Thighs
Single Most Likely Diagnosis
- Herpes Zoster (Shingles): Given the description of a blister in the inner thighs and lower back pain, herpes zoster is a strong consideration. The pain and blister are consistent with a dermatomal distribution, which is characteristic of shingles. The fact that the patient forgot to take their blood pressure medication is less directly relevant but could contribute to overall stress or discomfort.
Other Likely Diagnoses
- Contact Dermatitis: This could cause skin irritation and blisters, especially if the patient has come into contact with an allergen or irritant. Lower back pain could be unrelated or due to discomfort from the dermatitis.
- Folliculitis or Carbuncle: Bacterial infections of the hair follicles can cause abscesses and could be accompanied by lower back pain if the infection is severe or if the patient has a systemic response.
- Pilonidal Cyst or Abscess: Although typically found near the tailbone, a pilonidal cyst could cause lower back pain and might have a secondary infection leading to an abscess.
Do Not Miss Diagnoses
- Spinal Epidural Abscess: A serious condition that requires immediate medical attention. While less common, the combination of lower back pain and an abscess (if the blister is indeed an abscess) could suggest an infection spreading to the spinal epidural space.
- Necrotizing Fasciitis: A severe bacterial infection of the skin and subcutaneous tissues that can cause pain, blisters, and abscesses. It's a medical emergency due to its rapid progression and high mortality rate.
- Diabetic Foot Ulcer or Infection: If the patient has diabetes, uncontrolled blood pressure could exacerbate diabetic complications. Although the blister is in the inner thigh, diabetic patients are prone to various skin and soft tissue infections.
Rare Diagnoses
- Erythema Multiforme: An immune-mediated condition that can cause skin lesions, including blisters. It's often associated with infections or medications and could be considered if other causes are ruled out.
- Sweet Syndrome (Acute Febrile Neutrophilic Dermatosis): Characterized by fever, neutrophilia, and tender erythematous skin lesions, which could include blisters. It's a rare condition that might be associated with systemic diseases or medications.