Study guide
This chapter groups three organ systems that frequently overlap in primary care and urgent care encounters: the gastrointestinal tract, the musculoskeletal system, and the skin. Each section walks through history-taking clues, key diagnostic studies, and evidence-based treatment approaches for the conditions most often represented on the exam. Educational content only, not medical advice.
GERD and Peptic Ulcer Disease
Consider Maria, a 44-year-old woman with burning epigastric pain that worsens after meals and when lying flat, relieved partially by antacids. This history is classic for gastroesophageal reflux disease, caused by inappropriate relaxation of the lower esophageal sphincter allowing acidic gastric contents to irritate the esophagus. Alarm features that change the workup include dysphagia, unintentional weight loss, gastrointestinal bleeding, or onset after age 60, any of which prompt upper endoscopy rather than empiric treatment. Uncomplicated GERD is managed initially with lifestyle modification, including weight loss, avoiding late meals, and elevating the head of the bed, plus a trial of a proton pump inhibitor. Peptic ulcer disease shares overlapping symptoms but is distinguished by pain patterns: duodenal ulcers classically improve with food, while gastric ulcers may worsen with food. The two dominant causes are Helicobacter pylori infection and nonsteroidal anti-inflammatory drug use, and diagnostics include H. pylori testing via stool antigen, urea breath test, or biopsy during endoscopy. Treatment of H. pylori-positive ulcers requires eradication therapy combining a proton pump inhibitor with two antibiotics, commonly amoxicillin and clarithromycin, for 10 to 14 days. Complications to recognize include upper gastrointestinal bleeding, presenting as hematemesis or melena, and perforation, presenting as sudden severe abdominal pain with rigidity and free air under the diaphragm on upright chest radiograph, which is a surgical emergency.
Inflammatory Bowel Disease
Inflammatory bowel disease encompasses Crohn disease and ulcerative colitis, both immune-mediated conditions that a physician assistant must distinguish through history and diagnostics. Crohn disease can affect any part of the gastrointestinal tract from mouth to anus in a patchy, discontinuous pattern with transmural inflammation, often producing fistulas, strictures, and perianal disease; a classic vignette describes a young adult with right lower quadrant pain, diarrhea, weight loss, and perianal fistula. Ulcerative colitis, by contrast, is limited to the colon and rectum, involves continuous mucosal inflammation starting at the rectum, and typically presents with bloody diarrhea and tenesmus. Diagnostics for both conditions include colonoscopy with biopsy, which remains the gold standard, alongside inflammatory markers such as C-reactive protein and fecal calprotectin, which is elevated in intestinal inflammation and helps distinguish IBD from irritable bowel syndrome. Extraintestinal manifestations, including erythema nodosum, uveitis, and primary sclerosing cholangitis, appear in both conditions and are worth memorizing since they frequently appear in vignettes as a diagnostic clue. Treatment follows a stepwise approach: 5-aminosalicylates for mild ulcerative colitis, corticosteroids for flares, and immunomodulators or biologic agents such as tumor necrosis factor inhibitors for moderate to severe or refractory disease. Health maintenance considerations include monitoring for colorectal cancer risk with more frequent surveillance colonoscopy in long-standing disease, and bone density monitoring given chronic corticosteroid exposure.
Fractures, Arthritis, and Back Pain
Musculoskeletal complaints require careful attention to mechanism of injury and pattern recognition. A fall onto an outstretched hand in an older adult classically produces a distal radius fracture, while the same mechanism in a young athlete raises concern for a scaphoid fracture, notable for snuffbox tenderness and a risk of avascular necrosis if missed, since initial radiographs can appear normal. Ottawa ankle and knee rules help decide when radiography is warranted after acute injury, reducing unnecessary imaging. Arthritis questions require distinguishing patterns: osteoarthritis produces asymmetric joint pain that worsens with activity and improves with rest, typically affecting weight-bearing joints and the distal interphalangeal joints; rheumatoid arthritis produces symmetric small joint involvement with morning stiffness lasting more than an hour, positive rheumatoid factor and anti-cyclic citrullinated peptide antibodies, and can cause systemic symptoms. Gout presents with acute, exquisitely painful monoarticular arthritis, classically at the first metatarsophalangeal joint, with synovial fluid analysis showing negatively birefringent needle-shaped urate crystals, while pseudogout shows positively birefringent rhomboid calcium pyrophosphate crystals. Low back pain is overwhelmingly mechanical and self-limited, but red flags including saddle anesthesia, bowel or bladder dysfunction, and bilateral leg weakness suggest cauda equina syndrome, a surgical emergency requiring immediate MRI. Fever with back pain and intravenous drug use history should raise concern for vertebral osteomyelitis or epidural abscess.
Cellulitis and Common Dermatoses
Cellulitis presents as an area of warm, erythematous, poorly demarcated skin with tenderness and sometimes fever, most often caused by Streptococcus and Staphylococcus species entering through a break in the skin barrier. Treatment for uncomplicated cellulitis is oral antibiotics covering streptococci, such as cephalexin, while purulent lesions suggesting an abscess or methicillin-resistant Staphylococcus aureus warrant coverage with trimethoprim-sulfamethoxazole or doxycycline, often combined with incision and drainage. Necrotizing fasciitis is the critical diagnosis not to miss, distinguished by pain out of proportion to exam findings, rapidly spreading erythema, bullae, and systemic toxicity, requiring emergent surgical debridement. Among common dermatoses, psoriasis presents as well-demarcated, silvery scaled plaques over extensor surfaces such as elbows and knees, with nail pitting and a personal or family history common; treatment ranges from topical corticosteroids and vitamin D analogs for limited disease to systemic biologic agents for extensive or joint-involving disease. Atopic dermatitis, often seen in children with a personal or family history of atopy, presents as pruritic, poorly demarcated patches in flexural areas, managed with emollients and topical corticosteroids. Contact dermatitis follows exposure to an irritant or allergen and is typically well-demarcated, matching the pattern of contact. Recognizing a classic description, such as a well-demarcated linear rash after gardening suggesting poison ivy versus diffuse dry itchy patches in the antecubital fossae of an infant suggesting atopic dermatitis, is a frequently tested skill.
Key terms
- Alarm features (GI)
- — Warning symptoms such as dysphagia, weight loss, or bleeding that mandate endoscopy rather than empiric reflux treatment.
- Helicobacter pylori
- — A spiral gram-negative bacterium strongly associated with peptic ulcer disease, diagnosed by stool antigen, breath test, or biopsy.
- Fecal calprotectin
- — A stool biomarker of intestinal inflammation used to help distinguish inflammatory bowel disease from irritable bowel syndrome.
- Cauda equina syndrome
- — Compression of the lumbosacral nerve roots causing saddle anesthesia and bowel or bladder dysfunction; a surgical emergency.
- Rheumatoid factor / anti-CCP
- — Antibodies associated with rheumatoid arthritis; anti-CCP is more specific for the diagnosis.
- Negatively birefringent crystals
- — Needle-shaped urate crystals seen on synovial fluid polarized microscopy, diagnostic of gout.
- Necrotizing fasciitis
- — A rapidly progressive soft tissue infection causing pain out of proportion to exam findings, requiring emergent surgery.
- Ottawa ankle rules
- — A clinical decision tool used to determine whether ankle radiography is necessary after acute injury.
- Psoriasis
- — A chronic autoimmune skin condition producing well-demarcated silvery plaques on extensor surfaces, associated with nail changes and arthritis.
- Erythema nodosum
- — Tender, red nodules typically on the shins, an extraintestinal manifestation associated with inflammatory bowel disease.
Exam tips
- When a GI vignette mentions weight loss, bleeding, or dysphagia, choose endoscopy over an empiric medication trial as the next step.
- Distinguish Crohn disease from ulcerative colitis using the pattern of involvement: patchy and transmural versus continuous and mucosal.
- Memorize the crystal findings for gout versus pseudogout; polarized light microscopy questions are recurring exam favorites.
- Treat any back pain vignette with bowel, bladder, or bilateral neurologic findings as cauda equina syndrome until proven otherwise.
- For skin infections, look for pain out of proportion to exam findings as the clue that separates necrotizing fasciitis from ordinary cellulitis.