RHEUM & DERM

Question 1

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.

Answer 1

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.

Question 2

Describe intramembranous bone formation.

Answer 2

Formation of bone without a pre-existing cartilage matrix –flat bones such as the skull and rib cage develop this way.

Question 3

Characteristic lab findings in osteoporosis

Answer 3

Reduction in trabecular bone mass –> porous, weak bone. Serum calcium, phosphate, PTH, and alk phos are NORMAL. Labs exclude osteomalacia.

Question 4

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?

Answer 4

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.

Question 5

Name 3 ways active Vitamin D raises serum calcium and phosphate.

Answer 5

Intestines – increases absorption of Ca and phosphate
Kidney –increases reabsorption of Ca and phosphate
Bone –increases resorption of calcium and phosphate

Question 6

A patient with a hx of poor diet and renal failure presents with a fracture. What lab findings would you see?

Answer 6

Vit D deficiency (osteomalacia)
Decreased serum calcium and phosphate
Increased PTH and alkaline phosphatase

Question 7

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?

Answer 7

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.

Question 8

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?

Answer 8

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.

Question 9

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?

Answer 9

This is Gardner’s syndrome due to an APC mutation (same gene that mutates in FAP) on chromosome 5.

Question 10

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?

Answer 10

Osteoblastoma is larger (>2 cm), arises in vertebrae (not long bones), and presents as bone pain that does NOT respond to ASA.

Question 11

This is the most common benign bone tumor and may actually be a hamartoma.

Answer 11

Osteochondroma

Question 12

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?

Answer 12

Risk factors for osteosarcoma:
Familial retinoblastoma
Paget disease
Radiation exposure

Arises in metaphysis of long bones, usually the distal femur or proximal tibia.

Question 13

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?

Answer 13

Soap bubble appearance on xray

Epiphyseal end of long bones

Question 14

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.

Answer 14

This is Ewings sarcoma, a malignant proliferation of poorly-differentiated cells derived from neuroectoderm. 11;22 translocation is characteristic.

Question 15

This bone tumor classically arises in the medulla of small bones of the hands and feet. What is it?

Answer 15

Chondroma - benign

Question 16

This bone tumor arises in the medulla of the pelvis or central skeleton.

Answer 16

Chondrosarcoma - malignant

Question 17

Which muscles of the rotator cuff are responsible for lateral rotation of the arm? What about medial rotation?

Answer 17

Lateral: infraspinatus + teres minor
Medial: subscapularis

Question 18

3 most common ligaments injured in an ankle sprain, from most – > least common

Answer 18

Anterior talofibular
Calcaneofibular
Posterior talofibular

Question 19

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?

Answer 19

This is OA and usually the MCP is spared. Note that pain got worse with use.

Question 20

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.

Answer 20

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)

Question 21

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.

Answer 21

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)

Question 22

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.

Answer 22

Lesch-Nyhan syndrome
von Girke’s disease

This is Gout.

Question 23

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?

Answer 23

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.

Question 24

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?

Answer 24

This is Polymyositis characterized by endomysial inflammation with CD8+ T cells.

Question 25

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. PE reveals small purple papules on her DIP joints of both hands as well as a rash over her cheeks and eyelids. Name 5 lab findings you expect to find as well as the cells responsible for the inflammatory infiltrate.

Answer 25

This is Dermatomyositis mediated by CD4+ T cells. Increased CK, LDH, and aldolase levels as well as + ANA + anti-Jo-1 Abs are expected.

Question 26

What is the function of the protein that is absent in Duchenne muscular dystrophy?

Answer 26

Dystrophin connects skeletal muscle fibers and cardiac muscle fibers.

Question 27

What is the cause of Duchenne musuclar dystrophy?

Answer 27

Deleted dystrophin due to defective gene on X chromosome causing the degeneration of individual muslce fibers.

Question 28

What are 3 common locations for tophi in gout patients?

Answer 28

External ear
Olecranon bursa
Achilles tendon

Question 29

A patient presents with photosensitivity, arthritis, renal disease and recurrent oral ulcers is taking primaquine and NSAIDs. What type of checkup should she be receiving twice a year and what would be seen under light microscopy?

Answer 29

Renal evaluation –see wire loop lesions (circular thickening of BM)

Question 30

A 25 year old patient presents to you complaining of painful urination. On exam, you notice conjunctival inflammation of both eyes. He tells you that he recently had a bout of diarrhea that lasted for 3 days. What set of antigens corresponding to MHC Class I do you suspect is responsible for this patient’s disease?

Answer 30

This is reactive arthritis (Reiter’s sydndrome) that is associated with HLA-B27. It occurs post-GI (Shigella, Salmonella, Yersinia, Campylobacter, Clostridium) or chlamydia infections.

Question 31

A 23 year old male presents to your office complaining of joint stiffness. X-ray reveals fusion of joints, and you make the diagnosis of ankylosing spondylitis. What are 3 major manifestations you expect to find in this patient?

Answer 31

Uveitis

Aortic regurgitation and/or cardiac conduction abnormalities

Question 32

A patient presents with photosensitivity, arthritis, renal disease, and recurrent oral ulcers is taking primaquine and NSAIDs. Serum levels of which complement forms do you expect to be decreased?

Answer 32

C3, C4

Question 33

A 72 year old female presents complaining of recent weight loss, fever, and pain in her shoulders and hips. What lab findings do you expect, confirming your dx, and what disease is she most at risk for?

Answer 33

This is polymyalgia rheumatica which presents with elevated ESR and normal CK levels.
It is associated with temporal (giant cell) arteritis.

Question 34

A patient has diffiucltyswallowing, distal cyanosis in cold temperatures, and anti-centromere antibodies. What is the most likely cause of death?

Answer 34

CREST scleroderma – COD is most often sclerosis of the pulmonary system.

Question 35

Difference between albinism and vitiligo

Answer 35

Albinism has NORMAL melanocyte # with decreased melanin production
Vitiligo has DECREASED melanocyte #

Question 36

Patient presents with rash on the extensors. Skin scraping causes pinpoint bleeding. What are the changes in epidermal layers seen in this d/o?

Answer 36

This is classic psoriasis with an Auspitz sign. These pts have an increase in stratum spinosum and decrease in stratum granulosum.

Question 37

61 year old patient presents to your office with multiple flat, greasy keratin-filled cysts on his arms and abdomen. What are you most concerned about?

Answer 37

Leser-Trelat sign (sudden appearance of multiple seborrheic keratoses) can indicate an underlying malignancy (e.g., GI, lymphoid).

Question 38

61 year old woman presents with multiple crusty and weepy erythematous erosions. Immunofluorescence reveals antibodies around epidermal cells in a reticular or netlike pattern. Positive Nikolsky’s sign is observed. What is the pathogenesis of this d/o?

Answer 38

Pemphigus vulgaris is a potentially fatal autoimmune skin disorder with IgG antibody against desmoglein 3, a part of the desmosomes that is needed for cell-cell adhesions.

Question 39

61 year old woman presents with multiple intact, tense bullae with oral sparing. What is the most likely causative antibody?

Answer 39

IgG antibody against hemidesmosomes (epidermal basement membrane) –> Bullous pemphigoid.

Question 40

Patient presents with small, rough, erythematous papules and a dx of Actinic Keratosis is made. What is the risk associated with these lesions?

Answer 40

Risk of SCC is proportional to degree of epithelial dysplaisa.

Question 41

Name 7 causes of erythema nodosum.

Answer 41

Usually on anterior shins:

Sarcoidosis
Coccidiomycosis
Histoplasmosis
TB
Strep infections
Leprosy
Crohns

Question 42

6 Ps of Lichen Planus

Answer 42

Pruritic
Purple
Polygonal
Planar
Papules
Plaques

Question 43

Virus associated with Lichen Planus

Answer 43

Hepatitis C

Question 44

Skin disorder with a “Christmas tree” distribution and a collarette scale

Answer 44

Pityriasis rosea

Question 45

Patient presents to you concerned with a non-healing pearly ulcer with rolled edges on his nose. Histology reveals?

Answer 45

Palisading nuclei

This is Basal Cell CA

Question 46

Mutation that can drive progression of melanoma

Answer 46

Activating mutation in BRAF kinase