Differential Diagnosis
- Single most likely diagnosis
- Shingles (Herpes Zoster): This condition often starts with severe pain in a specific area, followed by a rash that can appear as a red bump with small pimple-like bumps. The pain and rash typically occur on one side of the body, which could include the back, under the shoulder area, and potentially radiate to the chest area. The sequence of events described, from pain to rash, is consistent with the progression of shingles.
- Other Likely diagnoses
- Costochondritis: This is an inflammation of the cartilage that connects the ribs to the breastbone, which can cause pain in the chest and breast area. It might also refer pain to the back. However, the appearance of a red bump with pimple-like bumps is less typical for costochondritis.
- Musculoskeletal strain: Strain in the back muscles could cause pain under the shoulder area and potentially in the chest if the strain affects muscles that connect to the chest wall. However, the development of a specific rash would be unusual for a simple musculoskeletal strain.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Pulmonary embolism: Although the symptoms described don't directly point towards a pulmonary embolism, severe chest pain can sometimes be a presenting symptom. The pain under the shoulder area could be referred pain from the lungs. It's crucial to consider this diagnosis due to its high mortality rate if untreated.
- Myocardial infarction (heart attack): Similar to pulmonary embolism, myocardial infarction can present with chest pain that might radiate to the back. While the rash is not typical for a heart attack, the combination of severe chest and back pain warrants consideration of cardiac causes.
- Rare diagnoses
- Dermatomyositis: This is an inflammatory disease characterized by skin rash and muscle weakness. While it could potentially explain some of the symptoms, the specific pattern of pain followed by a localized rash is less typical for dermatomyositis.
- Sarcoidosis: This condition can cause a wide range of symptoms, including skin rashes and musculoskeletal pain. However, the specific sequence and nature of symptoms described would be unusual for sarcoidosis.