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USMLE Step 1 practice exam flashcards > Pathoma > Flashcards

Pathoma Flashcards

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USMLE® Step 1 flashcards
1
Q

Achondroplasia

A

AD - impaired cartilage proliferation in the growth plate; common cause due to an activating mutation in fibroblast growth factor receptor 3 (FGFR3);

Most mutations are sporadic and related to increased paternal age.

poor endochondral bone formation; intramembranous bone formation is not affected = flat bones = normal head size

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2
Q

Osteogenesis imperfecta

A

autosomal dominant defect in collagen type 1 synthesis

Clinical features: Multiple fractures, hearing loss, blue sclera—thinning of scleral collagen reveals underlying choroidal veins.

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3
Q

Osteopetrosis

A

Abnormally thick heavy bone that fractures easily - defect of bone resorption

Carbonic anhydrase II mutation - acid required to remove calcium from bone –> can’t resorb bone

Bone fractures, anemia, thrombocytopenia, leukopenia, vision/hearding impairment (foramen thickening), hydrocephalus, renal tubular acidosis (w/ carbonic anhydrase deficiency).

Treat w/ bone marrow transplant - osteoclasts derived from monocytes

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4
Q

Rickets/osteomalacia

A

Defective osteoid mineralization - osteoid deposits

Low Vit D levels (resorb Ca and PO4 from intestine)

Rickets - kids <1 year bowing of leg in kids >1

Osteomalacia - weak bone w/ increased risk for fracture
Ca and phosphate decreased, PTH increased, All pos increased

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5
Q

Osteoperosis

A

Reduced trabecular bone mass –> porous bone w/ increased fracture risk

calcium, phosphate, and PTH are NORMAL vs. osteomalacia

Tx: Exercise, vit D, bisphosphanates - induce osteoclast apoptosis

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6
Q

Osteoblast activation

A

Increased alkaline phosphatase - need alkaline to lay down calcium.

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7
Q

Paget Dz of bone

A

Imbalance between osteoblast and osteoclast - localized process 1-2 bones

Osteoclast resorbs excess bone

Results in thick sclerotic bone - osteoblasts try to overcompensate - cement lines between bones - mosaic pattern of lamellar bone

Bone pain (micro fractures), increased hat size, hearing loss, lion-like facies

Isolated alk phos

Tx: Calcitonin (inhibit osteoclasts, opposite of PTH) and bisphosphanates

Complications: osteosarcoma and high-output cardiac output failure

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8
Q

Osteomyelitis

A

Bacteria in bone - mostly children (seed metaphysis) Adults (seed epiphysis)

S. aureus (most common), pseudomonas (IVDU), TB< pasteurella, N. Gonorrhea, Salmonella (sickle cell)

Bone pain w/ fever + leukocytosis, lytic focus surrounded by sclerosis on X-ray, Dx w/ blood culture

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9
Q

Osteoma

A

Benign

Surface of facial bones

a/w gardner (familial polyposis, fibromatosis, osteoma)

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10
Q

Osteid osteoma

A

Benign tumor of osteoblasts - rim of reactive bone

Young adults < 25 years in Cortex of long bones

Bone pain resolves w/ aspirin - bony mass w/ radiolucent core

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11
Q

Osteoblastoma

A

Benign tumor of osteoblasts

vs. osteoid osteopath - Larger, arises in vertebrae, presents are bone pain that isn’t ASA responsive

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12
Q

Osteochondroma

A

Benign - Tumor of bone w/ overlying cartilage cap

Cartilage can transform to chondrosarcoma

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13
Q

Osteosarcoma

A

Malignant osteoblast proliferation - teenagers most common

Risk factors: familial RB

Elederly - paget Dz of bone and radiation increase risk

Metaphysis of long boneDistal femur or proximal tibia

Presents as pathologic fracture, or bone pain and swelling

BX: large pleomorphic cells producing osteoid

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14
Q

Giant cell tumor

A

Giant cells w/ stroll cells - young adults

In epiphysis - ONLY ONE - Soap bubble on X-ray

Locally aggressive

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15
Q

Ewing sarcoma

A

Poorlydifferentiated - derived from neuroectoderm

In diaphysis of long bone in young males

Onion skin appearance on X-ray

Easily confused w/ osteomyelitis - fever

(11:22) translocation - chemorpsponsive

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16
Q

Chondroma

A

Benign - cartilage tumor

Occur in small bones - hands/feet

arises in medulla

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17
Q

Chondrosarcoma

A

Malignant cartilage tumor

Occur in pelvis/ central skeleton

arises in medulla

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18
Q

Bony metastasis

A

Most common bone malignancy- mostly osteolytic (punched out)

Prostate cancer is osteoblastic

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19
Q

HLA DR4

A

Rheumatoid arthritis - synovitis + pannus (inflamed granulation tissue) - DIP spared

Rheumatoid factor - IgM ab against Fc portion of IgG

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20
Q

HLA-B27

A

seronegative spondyloarthropathies: Psoriatic arthritis, ankylosing spondylitis, and Reiter syndrome

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21
Q

Ankylosing spondylarthritis

A

sacroiliac joints and spine - male young adults

involvement of vertebral bodies eventually arises, leading to fusion of the vertebrae (‘bamboo spine ).

uveitis and aortitis (leading to aortic regurgitation).

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22
Q

Reiter syndrome

A

arthritis, urethritis, and conjunctivitis after GI or chlamydia infection (can’t see, can’t pee, can’t climb a tree)

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23
Q

Psoriatic arthritis

A

In 10% of cases of psoriasis.

Involves axial and peripheral joints; DIP joints of the hands and feet are most commonly affected, leading to “sausage” fingers or toes.

24
Q

Infectious arthritis

A

Causes include: N. Gonorrhea— most common, sexually active young adult, S aureus—older children and adults;

single joint, usually the knee, warm with limited range of motion; fever, increased white count, and elevated ESR are often present.

Treat immediately

25
Q

Secondary gout

A

Lesch-nyhan

Leukemia/myeloproliferative disorders

renal insufficiency (decreased uric acid excretion)

26
Q

Chronic gout

A

Tophi

Renal failure—Urate crystals may deposit in kidney tubules (urate nephropathy)

27
Q

Pseudogout

A

deposition of calcium pyrophosphate dihydrate (CPPD);

synovial fluid shows rhomboid-shaped crystals with weakly positive birefringence under polarized light.

28
Q

Dermatomyositis

A

Inflammatory disorder of the skin and skeletal muscle, some cases are associated with carcinoma (e.g., gastric) consider underlying carcinoma

Bilateral proximal muscle weakness; distal involvement can develop late in disease. Rash of the upper eyelids (heliotrope rash); malar rash. Red papules on the elbows, knuckles, and knees (Grotton lesion)

Laboratory findings: Increased creatinine kinase, Positive ANA and anti-jo-l antibody

Bx: Perimysial inflammation (CD4+ T cells) with perifascicular atrophy on biopsy

Tx: corticosteroids.

29
Q

Polymyositis

A

Inflammatory disorder of skeletal muscle

Resembles dermatomyositis clinically, but skin is not involved

Bx: endomysial inflammation (CD4+ T cells) with necrotic muscle fibers

30
Q

X-linked (duchenne) Muscular dystrophy

A

Replacement of muscle with adipose

Deletions of dystrophin (linker molecule) - mostly spontaneous

Elevated creatinine kinase

death from cardiac or respiratory failure

31
Q

Becker muscular dystrophy

A

Mutation of dystrophin vs. deletion in duchenne

Milder disease than duchenne, appears later in childhood

32
Q

Lambert eaton

A

Proximal muscular weakness

Autoantibodies against pre-synaptic calcium channels

Paraneoplastic - small cell lung cancer

33
Q

Thymoma/thymic hyperplasia

A

a/w myasthenia gravis

34
Q

Lipoma

A

Benign tumor of adipose tissue

Most common benign soft tissue tumor in adults

35
Q

Liposarcoma

A

Malignant tumor of adipose tissue

Most common malignant soft tissue tumor in adults

Lipoblast is the characteristic cell.

36
Q

Rhabdomyoma

A

Benign tumor of skeletal muscle

Cardiac rhabdomyoma is associated with tuberous sclerosis.

37
Q

Rhabdomyosarcoma

A

Malignant tumor of skeletal muscle

Most common malignant soft tissue tumor in children

Rhabdomyoblast is the characteristic cell; desmin positive

Mos tcommon site is the head and neck; vagina is the classic site in young girls.

38
Q

Layers of the skin

A

Epidermis is comprised of keratioocytes and has four layers

  1. Stratum basalis—regenerative (stem cell) layer
  2. Stratum spinosum—characterized by desmosomes between keratinocytes
  3. Stratum granulosum—characterized by granules in keratinocytes
  4. Stratum corneum—characterized by keratin in anucleate cells
39
Q

Dermis

A

connective tissue, nerve endings, blood and lymphatic vessels, and adnexal structures (e.g., hair shafts, sweat glands, and sebaceous glands).

40
Q

Psoriasis

A

Excessive keratinocyte proliferation

Acanthosis - epidermal hyperplasia

Parakeratosis - hyperkeratosis with retention of keratinocyte nuclei in the stratum comeum) –> silvery scale

Thinning of the epidermis above elongated dermal papillae; results in bleeding when scale is picked off (Auspitz sign)

41
Q

Lichen planus

A

Pruritic, planar, polygonal, purple papules, often with reticular white
lines on their surface (Wickham striae); commonly involves wrists, elbows, and oral mucosa
I, Oral involvement manifests as Wickham striae,

Histology shows inflammation of the dermal-epidermal junction with a ‘saw-tooth’ appearance

a/wchronic hepatitis C virus infection

42
Q

Pemphigus vulgaris

A

IgG antibody against desmoglein (type II hypersensitivity)

Acantholysis (separation) of stratum spinosum keratinocytes (normally
connected by desmosomes) results in suprabasal blisters.

Basal layer cells remain attached to basement membrane via hemidesmosomes
(‘tombstone’ appearance)

NIkolsky sign: Thin-walled bullae rupture easily, leading to shallow erosions
with dried crust.

Immunofluorescence highlights IgG surrounding keratinocytes in a ‘fish net’ pattern.

43
Q

Bullous pemphigoid

A

Autoimmune destruction of hem idesmo somes between basal cells and basement membrane

IgG antibody against basement membrane collagen (type 4)

Oral mucosa is spared.

Basal cell layer is detached from the basement membrane

clinically milder than pemphigus vulgaris

Immunofluorescence highlights IgG along basement membrane (linear pattern).

44
Q

Dermatitis herpetiformis

A

Autoimmune deposition of IgA at the tips of dermal papillae

pruritic vesicles and bullae that are grouped (herpetiform)

Strong association with celiac disease; resolves with gluten-free diet

45
Q

Erythema multiforme

A

Hypersensitivity reaction characterized by targeloid rash and bullae (central epidermal necrosis)

HSV infection

SJS when there is oral mucosa/lip involvement and fever.

Toxic epidermal necrolysis: severe form of SJS characterized by diffuse sloughing of skin, d/t adverse drug reaction

46
Q

Lesser treat sign

A

sudden onset of multiple seborrheic keratoses and suggests underlying carcinoma of the GI tract

47
Q

Basal cell carcinoma

A

Presents as an elevated nodule with a central, ulcerated crater surrounded by dilated (telangiectatic) vessels, ‘pink, pearl-like papule’

Classic location is the upper lip.

Histology shows nodules of basal cells with peripheral palisading

Surgically excise, metastasis rare

48
Q

Squamous cell carcinoma

A

Presents as an ulcerated, nodular mass, usually on the face (lower lip)

Excise, metastasis is uncommon.

Actinic keratosis is a precursor lesion of squamous cell carcinoma and presents as a
hyperkeratotic, scaly plaque, often on the face, back, or neck.

Keratoacanthoma is well-differentiated squamous cell carcinoma that develops
rapidly and regresses spontaneously; presents as a cup-shaped tumor filled with keratin debris

49
Q

Melanocytes

A

Responsible for pigmentation - present in the basal layer

Derived from neural crest

Synthesize melanin in melanosomes using tyrosine as a precursor molecule

50
Q

Vitiligo

A

Localized loss of skin pigmentation due to autoimmune destruction of melanocytes

51
Q

Albinism

A

Enzyme deficiency (usually tyrosinase) that impaired melanin PRODUCTION

Increased risk of squamous cell carcinoma, basal cell carcinoma, and melanoma due
to reduced protection against UVB

52
Q

Freckle (ephesus)

A

Due to increased number of melanosomes (melanocytes are not increased)

53
Q

Melasma

A

Mask-like hyperpig mentation of the cheeks

Associated with pregnancy and oral contraceptives

54
Q

Staphylococcal scalded skin syndrome

A

Sloughing of skin with erythematous rash and fever; leads to significant skin loss

Due to S aureus infection; exfoliative A and B toxins result in epidermolysis of the stratum granulosum.

Distinguished histologically from toxic epidermal necrolysis by level of skin
separation; separation in TEN occurs at the dermal-epidermal junction.

55
Q

Transthyretin

A

Senile cardiac amyloidosis

56
Q

CD14

A

TLR on macrophages that recognizes LPS

USMLE Step 1 practice exam flashcards (16 decks)

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