Differential Diagnosis for 42 yo with Severe Acute LBP, Chronic Diarrhea, High LFTs, ANA Pos, and Facial Rash

• Single Most Likely Diagnosis
  • Inflammatory Bowel Disease (IBD) with associated conditions: Given the history of chronic diarrhea, high liver function tests (LFTs), and the presence of a facial rash, IBD (such as Crohn's disease or ulcerative colitis) is a strong consideration. The acute lower back pain (LBP) could be related to ankylosing spondylitis or other spondyloarthropathies, which are known to be associated with IBD. The positive ANA could be seen in some cases of IBD, although it's more commonly associated with autoimmune diseases like lupus, which has been ruled out here.
• Other Likely Diagnoses
  • Spondyloarthritis (e.g., ankylosing spondylitis, psoriatic arthritis): These conditions can cause severe back pain and are associated with various extra-articular manifestations, including gastrointestinal symptoms and skin rashes. The presence of ANA positivity, while not typical, does not rule out these diagnoses.
  • Autoimmune Hepatitis: Given the high LFTs and positive ANA, autoimmune hepatitis is a consideration, especially if the patient has other symptoms like fatigue or jaundice. However, the primary presentation of severe acute LBP and chronic diarrhea makes this less likely as the single most likely diagnosis.
• Do Not Miss Diagnoses
  • Spinal Infection (e.g., discitis, osteomyelitis): Infections of the spine can present with severe back pain and can be life-threatening if not promptly treated. The absence of trauma does not rule out this possibility, especially if the patient has a compromised immune system or an underlying condition that predisposes to infection.
  • Cauda Equina Syndrome: A neurological emergency that can present with severe lower back pain, among other symptoms like bladder and bowel dysfunction. Prompt recognition and treatment are crucial to prevent long-term neurological damage.
• Rare Diagnoses
  • Sarcoidosis: This systemic granulomatous disease can affect multiple organs, including the liver (causing elevated LFTs), skin (causing rashes), and joints (causing back pain). While it's a less common diagnosis, its multisystem nature could explain the patient's diverse symptoms.
  • Whipple's Disease: A rare, systemic bacterial infection that can cause chronic diarrhea, weight loss, and arthralgias, among other symptoms. It's a diagnosis of exclusion but should be considered in patients with unexplained, multisystem disease.