RHEUM & DERM Flashcards
A patient presents with short arms and legs but a normal sized torso and head. Describe the mutation involved in the pathogenesis of this disease.
Achondroplasia is due to an ACTIVATING mutation in the fibroblast growth factor receptor 3 (FGFR3) –overexpression actually inhibits growth. It causes poor ENDOCHONDRAL bone formation which is characterized by the formation of a cartilage matrix which is then replaced by bone and the mechanism by which long bones grow.
Describe intramembranous bone formation.
Formation of bone without a pre-existing cartilage matrix –flat bones such as the skull and rib cage develop this way.
Characteristic lab findings in osteoporosis
Reduction in trabecular bone mass –> porous, weak bone. Serum calcium, phosphate, PTH, and alk phos are NORMAL. Labs exclude osteomalacia.
Patient presents with a hx of multiple fractures as well as hearing impairment. Labs show anemia, thrombocytopenia, and leukopenia. What mutation is present and what effect does this have on the kidneys?
Osteopetrosis – carbonic anhydrase II mutation leads to loss of the acidic micro-environment required for bone resorption. Renal tubular acidosis is seen because the lack of carbonic anhydrase results in decreased tubular reabsorption of HCO3-, leading to metabolic acidosis.
Anemia, thrombocytopenia, and leukopenia are seen with extramedullary hematopoiesis because this is a myelophthisic process.
Name 3 ways active Vitamin D raises serum calcium and phosphate.
Intestines – increases absorption of Ca and phosphate
Kidney –increases reabsorption of Ca and phosphate
Bone –increases resorption of calcium and phosphate
A patient with a hx of poor diet and renal failure presents with a fracture. What lab findings would you see?
Vit D deficiency (osteomalacia)
Decreased serum calcium and phosphate
Increased PTH and alkaline phosphatase
A patient presents to you because of bone pain and hearing loss. She also mentions to you that she feels like her head is getting bigger. What do you expect to see on biopsy and what are characteristic lab findings?
This is Paget Disease of the bone, and bx would reveal a mosaic pattern of lamellar bone. This is the MOST COMMON cause of ISOLATED elevated alkaline phosphatase in patients >40 years old.
A 5 year old patient presents to you with budding breasts and unilateral cafe au lait spots. What other findings do you expect to see?
This is McCune Albright syndrome, a subset of Polyostotic fibrous dysplasia. You’d expect to see multiple unilateral bone lesions due to the bone being replaced by fibroblasts, collagen, and irregular bony trabeculae.
Patient presents with a cotton wool appearance to the jaw, multiple lipomas, and is found to have several colonic polyps. What mutation caused this disease?
This is Gardner’s syndrome due to an APC mutation (same gene that mutates in FAP) on chromosome 5.
23 y.o. male patient presents with bone pain in their femur. Imaging reveals a bony mass with a radiolucent core. How do you determine if it is an osteoid osteoma or an osteoblastoma?
Osteoblastoma is larger (>2 cm), arises in vertebrae (not long bones), and presents as bone pain that does NOT respond to ASA.
This is the most common benign bone tumor and may actually be a hamartoma.
Osteochondroma
17 year old girl presents with pain in her femur accompanied by swelling. Imaging reveals a destructive mass with a “sunburst” appearance and lifting of the periosteum. Name 3 risk factors for this disease and where it tends to arise?
Risk factors for osteosarcoma:
Familial retinoblastoma
Paget disease
Radiation exposure
Arises in metaphysis of long bones, usually the distal femur or proximal tibia.
24 year old male presents with an osteoclastoma just distal to the knee. What is the classic appearance on xray and where does this tumor arise?
Soap bubble appearance on xray
Epiphyseal end of long bones
11 year old boy presents with a bone tumor in his scapula. On x-ray, it has an onion skin appearance and biopsy reveals small, round blue cells that resemble lymphocytes. Name the classic translocation and where these proliferative cells originated.
This is Ewings sarcoma, a malignant proliferation of poorly-differentiated cells derived from neuroectoderm. 11;22 translocation is characteristic.
This bone tumor classically arises in the medulla of small bones of the hands and feet. What is it?
Chondroma - benign
This bone tumor arises in the medulla of the pelvis or central skeleton.
Chondrosarcoma - malignant
Which muscles of the rotator cuff are responsible for lateral rotation of the arm? What about medial rotation?
Lateral: infraspinatus + teres minor
Medial: subscapularis
3 most common ligaments injured in an ankle sprain, from most – > least common
Anterior talofibular
Calcaneofibular
Posterior talofibular
Obese 56 y.o woman presents with knee pain that she says is only relieved with rest. Which part of the joint is typically spared in this disease?
This is OA and usually the MCP is spared. Note that pain got worse with use.
Obese 56 y.o. presents with a cyst in her popliteal fossa and ulnar deviation of the fingers. You also see synovitis present. Name 2 antibodies and the HLA associated with this disease.
Rheumatoid Arthritis
Rheumatoid factor (IgM autoantibody against Fc portion of IgG)
Anti-cyclic citrullinated peptide Ab is more specific
HLA-DR4
Hint: Rheumatoid FOURTHritis (DR4)
Serena Williams presents to your office saying her eyes are always dry, despite consistently using eye drops to relieve this. You note dry mucous membranes and parotid enlargement on P.E. What 2 diseases is Serena at increased risk for and name 2 Abs found in her serum.
Remember with Sjogrens, you can’t see, can’t spit, and can’t climb shit (also has arthritis usually).
Increased risk of B cell lymphoma and dental caries.
Autoantibodies to ribonucleoprotein antigens SS-A (Ro) and SS-B (La)
A 45 y.o. mediterranean man presents with pain and swelling of the knees, subcutaneous nodules around the joints and Achilles tendon, and equisite pain in the metatarsophalangeal joint of his right big toes. Bx reveals needle-like crystals. Name 2 congenital diseases associated with this disorder.
Lesch-Nyhan syndrome
von Girke’s disease
This is Gout.
A 65 y.o. mediterranean man presents with pain and swelling of the knees, subcutaneous nodules around the joints and Achilles tendon, and equisite pain in the metatarsophalangeal joint of his right big toes. Bx reveals rhomboid crystals. What are these crystals made of?
This is pseudogout caused by the deposition of calcium pyrophosphate crystals within the joint space –> weakly positively birefringent. Also, these crystals are BLUE when parallel to the light whereas in gout, crystals are yellow when parallel.
A 46 y.o. woman presents to you complaining of bilateral pain and weakness in her shoulders that is so severe she feels weak even brushing her hair in the morning. Lab tests reveal increased CPK and aldolase levels. Serum anti-Jo Abs and ANA are both positive. What are the main cells responsible for the lymphocytic inflammation?
This is Polymyositis characterized by endomysial inflammation with CD8+ T cells.
