Step 1 Musculoskeletal, Skin, and Connective Tissue
Musculoskeletal, skin, and connective tissue accounts for roughly 10% of USMLE Step 1 content. Bone pathology, inflammatory arthritis, connective tissue diseases, and dermatology all live here. The organ systems feel unrelated but share a common exam logic: mechanism drives management, and lab patterns distinguish diagnoses that look clinically similar. If you are looking for high-yield MSK and dermatology topics for Step 1, the look-alike pairs below generate questions every exam cycle.
Many questions in this area are clinical vignettes requiring you to distinguish conditions with overlapping presentations. Osteoporosis vs osteomalacia, gout vs pseudogout, pemphigus vs pemphigoid, osteosarcoma vs Ewing — these pairs show up repeatedly because they require precise mechanistic and histologic reasoning, not just recognition. Students consistently reverse the birefringence: gout crystals are negatively birefringent (yellow when parallel to the compensator) while pseudogout crystals are positively birefringent. Connective tissue diseases are heavily antibody-tested, and the exam loves to swap anti-dsDNA for anti-Smith or anti-histone and check whether you notice.
Step 1 MSK pharmacology is integrated throughout: bisphosphonate mechanism, MTX toxicity and folate rescue, TNF inhibitor TB screening, isotretinoin monitoring, and gout drug timing are all high-frequency. Another misconception that costs points: starting allopurinol during an acute gout flare can paradoxically worsen the attack by mobilizing urate crystals. Pattern recognition is necessary but not sufficient — you need to know why each answer is correct, and that is what USMLE musculoskeletal questions reward.
Bone Cells and Matrix
RANK/RANKL/OPG axis, osteoblast vs osteoclast markers, and PTH dosing-dependent anabolic vs catabolic effects.
- Confuses alkaline phosphatase as an osteoclast marker rather than an osteoblast marker
- Confuses the cellular source of RANKL as osteoclasts rather than osteoblasts
Endochondral vs Membranous Ossification
Flat bones form via intramembranous ossification; FGFR3 gain-of-function drives achondroplasia's autosomal dominant inheritance.
- Confuses skull flat bone formation as endochondral rather than intramembranous
- Confuses achondroplasia FGFR3 mutation as loss-of-function rather than gain-of-function
Fracture Healing Stages
Sequential stages from hematoma to remodeling, and factors like corticosteroids that impair healing.
- Confuses the order of callus formation, placing hard callus before soft callus
- Missing that corticosteroids impair fracture healing through multiple mechanisms
Compartment Syndrome
Early pain-out-of-proportion signs, delta-P fasciotomy threshold, and why elevation is contraindicated.
- Confuses absent pulse as an early finding in compartment syndrome rather than a late sign
- Confuses fasciotomy threshold as an absolute pressure rather than delta-P relative to diastolic BP
Osteoporosis
Normal calcium and ALP distinguish this from osteomalacia; T-score ≤−2.5 and bisphosphonate mechanism are high-yield.
- Confuses osteoporosis with osteomalacia by expecting abnormal calcium or ALP labs
- Confuses the DEXA T-score threshold for osteoporosis, misplacing it at -1.5 instead of -2.5
Osteomalacia and Rickets
Vitamin D deficiency produces low calcium, low phosphate, and elevated ALP with characteristic skeletal deformities in children.
- Confuses the lab pattern of vitamin D deficiency, expecting high rather than low calcium and phosphate
- Confuses osteomalacia with osteoporosis by expecting normal ALP in both conditions
Paget Disease of Bone
Elevated alkaline phosphatase with normal calcium, osteolytic-to-sclerotic phases, and osteosarcoma as a long-term complication.
- Confuses Paget disease lab hallmark as elevated calcium rather than elevated alkaline phosphatase
- Confuses the initial phase of Paget disease as sclerotic rather than osteolytic
Avascular Necrosis (Osteonecrosis)
Fat emboli from corticosteroids cause femoral head osteonecrosis; MRI detects it far earlier than plain X-ray.
- Confuses the mechanism of corticosteroid-induced AVN as thrombotic rather than fat emboli/lipid accumulation
- Confuses Osgood-Schlatter with Legg-Calvé-Perthes by misidentifying the anatomic site and mechanism
Osteomyelitis
S. aureus dominates all ages; MRI outperforms plain X-ray early; diabetic foot requires distinguishing from Charcot.
- Confuses S. aureus as an adult-only pathogen in osteomyelitis when it dominates all age groups
- Confuses plain X-ray as the preferred imaging for osteomyelitis when MRI is more sensitive early
Septic Arthritis
N. gonorrhoeae leads in sexually active adults; aspirate before antibiotics; synovial WBC >50,000 is the diagnostic threshold.
- Confuses S. aureus as the dominant pathogen in young adult septic arthritis when N. gonorrhoeae is more common in sexually active patients
- Confuses the order of management by starting antibiotics before joint aspiration in septic arthritis
Osteosarcoma
Metaphyseal location, Codman triangle and sunburst sign on X-ray, and osteoid matrix distinguish this from Ewing sarcoma.
- Confuses osteosarcoma location with Ewing sarcoma diaphyseal/flat bone predilection
- Misattributes Codman triangle and sunburst X-ray sign to Ewing sarcoma instead of osteosarcoma
Ewing Sarcoma
Translocation t(11;22), neuroectodermal origin, diaphyseal lytic lesion with fever — easily mistaken for osteomyelitis in children.
- Confuses Ewing sarcoma translocation t(11;22) with the Philadelphia chromosome t(9;22)
- Misidentifies Ewing sarcoma cell of origin as osteoblastic rather than neuroectodermal
Benign Bone Tumors
Giant cell tumor at the epiphysis, osteoid osteoma's NSAID-responsive nocturnal pain, and osteochondroma's low malignant risk.
- Confuses giant cell tumor epiphyseal location with osteosarcoma metaphyseal location
- Misses the hallmark NSAID-responsive nocturnal pain pattern of osteoid osteoma
Chondrosarcoma
Adults with chondroid matrix production — contrasts with osteosarcoma's adolescent peak and osteoid production.
- Confuses chondrosarcoma adult demographics with the adolescent peak of osteosarcoma
- Confuses chondroid matrix production of chondrosarcoma with osteoid production of osteosarcoma
Osteoarthritis
Mechanical cartilage wear produces brief morning stiffness, DIP/PIP/first CMC involvement, and classic X-ray LOSS findings.
- Misclassifies osteoarthritis as an inflammatory arthritis rather than a degenerative mechanical process
- Confuses OA brief morning stiffness (<30 min, improves with use) with RA prolonged stiffness (>1 hour)
Rheumatoid Arthritis
Pannus erosion at MCPs/PIPs/wrists, anti-CCP specificity, prolonged morning stiffness, and TNF inhibitor TB screening.
- Overestimates RF specificity and undervalues anti-CCP as the more specific RA antibody
- Confuses RA immune-mediated pannus erosion with the mechanical cartilage wear of OA
Gout
Negatively birefringent urate crystals, first MTP attacks, and the rule against starting allopurinol during an acute flare.
- Reverses birefringence: gout crystals are negatively birefringent (not positive), pseudogout crystals are positively birefringent
- Incorrectly initiates allopurinol during an acute gout attack rather than waiting until the flare resolves
Pseudogout (CPPD)
Positively birefringent calcium pyrophosphate crystals preferentially deposit in the knee; urate-lowering therapy has no role.
- Confuses CPPD crystal morphology and birefringence with monosodium urate crystals
- Misassigns first MTP joint involvement to pseudogout; pseudogout preferentially affects the knee
Seronegative Spondyloarthropathies
HLA-B27-linked, seronegative arthritides — AS, psoriatic, reactive, IBD-associated — with distinct axial and extra-articular patterns.
- Confuses seronegative spondyloarthropathy HLA-B27 association with the RF/anti-CCP seropositivity of RA
- Misidentifies the reactive arthritis triad; it is urethritis + conjunctivitis + arthritis, not rash
Juvenile Idiopathic Arthritis
Systemic JIA has evanescent rash with fever; asymptomatic uveitis requires scheduled screening regardless of symptoms.
- Confuses the evanescent fever-associated rash of systemic JIA with the fixed malar rash of SLE
- Misses that JIA uveitis is often asymptomatic and requires scheduled ophthalmologic screening, not symptom-driven evaluation
Systemic Lupus Erythematosus (SLE)
Anti-dsDNA and anti-Smith are most specific; ANA is only a screen; SOAP BRAIN MD criteria and drug-induced lupus round out testing.
- Confuses anti-dsDNA and anti-Smith in terms of which is most specific for SLE
- Treats positive ANA as diagnostic of SLE rather than a sensitive screening test
Systemic Sclerosis (Scleroderma)
Anti-centromere marks limited/CREST; anti-Scl-70 marks diffuse; ACE inhibitors — not steroids — are lifesaving in renal crisis.
- Reverses the antibody associations for limited vs diffuse scleroderma
- Prescribes steroids instead of ACE inhibitors for scleroderma renal crisis
Sjögren Syndrome
Anti-Ro/SSA drives congenital heart block in neonates; MALT lymphoma is the associated malignancy, not Hodgkin.
- Treats anti-Ro and anti-La as equivalent rather than understanding their different sensitivity/specificity profiles
- Attributes neonatal lupus/congenital heart block to anti-dsDNA rather than anti-Ro/SSA antibodies
Mixed Connective Tissue Disease
Anti-U1 RNP antibody defines this overlap syndrome; Raynaud phenomenon and swollen hands are hallmark early features.
- Confuses the defining antibody of MCTD (anti-U1 RNP) with ANA or anti-dsDNA
- Misses that Raynaud phenomenon and swollen hands are hallmark early features of MCTD
Polymyositis and Dermatomyositis
Dermatomyositis adds heliotrope rash, Gottron papules, and strong malignancy risk to the proximal weakness of inflammatory myopathy.
- Confuses IBM's asymmetric distal-predominant weakness pattern with the proximal symmetric weakness of polymyositis
- Fails to distinguish dermatomyositis's strong malignancy association from the lower risk in polymyositis
Polymyalgia Rheumatica
Normal CK with elevated ESR/CRP, shoulder/hip girdle pain, and much higher steroid doses needed when GCA co-occurs.
- Expects elevated CK in PMR rather than normal muscle enzymes with elevated inflammatory markers
- Uses the same steroid dose for PMR and GCA rather than recognizing GCA requires much higher doses
Fibromyalgia
All laboratory studies are normal; opioids are specifically avoided; exercise and SNRIs/TCAs anchor treatment.
- Expects abnormal inflammatory labs in fibromyalgia rather than universally normal laboratory studies
- Considers opioids for fibromyalgia pain rather than recognizing they are specifically avoided
Myasthenia Gravis
Postsynaptic AChR antibodies cause fatigable weakness that worsens with use, opposite to Lambert-Eaton's transient improvement.
- Confuses the fatigability pattern of MG (worsens with use) with Lambert-Eaton (transiently improves with use)
- Misplaces the MG antibody target to presynaptic calcium channels instead of postsynaptic AChR
Muscular Dystrophies
DMD and Becker share the dystrophin gene but differ by mutation type; myotonic dystrophy is autosomal dominant with trinucleotide repeat expansion.
- Attributes DMD and Becker to different genes rather than different mutation types in the same dystrophin gene
- Misclassifies myotonic dystrophy as X-linked recessive rather than autosomal dominant with trinucleotide repeat expansion
Malignant Hyperthermia
RYR1 mutation causes hypercapnia and rigidity with volatile anesthetics/succinylcholine; dantrolene blocks SR calcium release.
- Fails to distinguish MH-triggering agents (volatile anesthetics, succinylcholine) from safe alternatives like propofol
- Identifies hyperthermia as the earliest MH sign rather than hypercapnia and muscle rigidity
Neuroleptic Malignant Syndrome
Dopamine receptor blockade causes lead-pipe rigidity over days; clonus and hyperreflexia point to serotonin syndrome instead.
- Confuses NMS mechanism as dopamine excess rather than dopamine receptor blockade
- Confuses the muscle findings of NMS (lead-pipe rigidity) with serotonin syndrome (clonus/hyperreflexia)
Rhabdomyolysis
Positive dipstick with no RBCs, direct myocyte K+ release, and calcium deposition in necrotic muscle drive the electrolyte picture.
- Confuses myoglobinuria (positive dipstick, no RBCs on microscopy) with true hematuria
- Attributes rhabdomyolysis hyperkalemia solely to AKI rather than also to direct K+ release from lysed myocytes
Brachial Plexus
Erb (C5–C6) vs Klumpke (C8–T1) root levels, long thoracic nerve winging, and radial vs axillary nerve injury patterns.
- Reverses the root levels of Erb palsy (C5–C6) and Klumpke palsy (C8–T1)
- Confuses scapular winging (long thoracic nerve / serratus anterior) with axillary nerve injury
Lumbosacral Plexus
Common peroneal nerve causes foot drop; superior gluteal nerve weakness produces Trendelenburg gait, not femoral nerve.
- Confuses foot drop causation — attributes it to tibial nerve rather than common peroneal nerve injury
- Misattributes Trendelenburg gait to femoral nerve injury rather than superior gluteal nerve / gluteus medius weakness
Rotator Cuff Injury and Tear
Supraspinatus is the most commonly torn SITS muscle; empty-can tests it specifically; drop-arm suggests complete tear.
- Incorrectly includes the biceps tendon as a rotator cuff component instead of recognizing SITS muscles only
- Confuses the most commonly torn rotator cuff muscle — supraspinatus, not infraspinatus
Lateral and Medial Epicondylitis
Resisted wrist extension provokes lateral (extensor) epicondylitis; resisted flexion provokes medial (flexor) epicondylitis.
- Reverses the muscle groups involved in lateral (extensors) vs medial (flexors) epicondylitis
- Confuses provocative maneuvers — resisted wrist extension tests lateral epicondylitis, not medial
Costochondritis
Reproducible chest wall tenderness distinguishes this from cardiac pain; Tietze syndrome adds visible swelling at the junction.
- Misinterprets reproducible chest wall tenderness as consistent with cardiac chest pain rather than as a key feature of costochondritis
- Missing the distinction between costochondritis (no swelling) and Tietze syndrome (visible/palpable swelling at costochondral junction)
Ganglion Cyst
Fluid-filled dorsal wrist mass that transilluminates; observation or aspiration precedes surgical excision.
- Confuses transillumination findings — ganglion cysts transilluminate because they are fluid-filled
- Overestimates the need for surgical excision of ganglion cysts when observation or aspiration is usually first-line
Scoliosis
Bracing at 25–40°, surgery above 40–50°; idiopathic form disproportionately affects girls and causes restrictive lung disease.
- Confuses Cobb angle thresholds — bracing is for 25–40°, surgery for >40–50°
- Assumes equal sex distribution in idiopathic scoliosis when girls are disproportionately affected and at higher risk for progression
Clavicle Fracture
Middle third fractures dominate; lateral fractures risk coracoclavicular ligament disruption and nearby vascular/brachial plexus injury.
- Misidentifies the most common clavicle fracture location as medial rather than middle third
- Missing awareness that clavicle fractures carry risk of subclavian vessel or brachial plexus injury and that lateral fractures may disrupt coracoclavicular ligaments
Hip Dislocation
Posterior dislocation flexes and internally rotates the leg and injures the sciatic nerve; reduce within 6 hours to limit AVN.
- Confuses limb positioning of anterior vs posterior hip dislocation
- Misses the 6-hour reduction window to minimize AVN risk
Knee Ligament and Meniscus Injuries
Lachman test is more sensitive than anterior drawer for ACL; posterior drawer identifies PCL; valgus stress tests the MCL.
- Confuses Lachman test with anterior drawer test as the more sensitive ACL exam
- Confuses posterior drawer test as an ACL rather than PCL finding
Ankle Sprain
Inversion injures lateral ligaments; Ottawa rules guide X-ray use only, not MRI ordering.
- Confuses inversion vs eversion mechanism and which ligament complex is injured
- Misidentifies Ottawa rules as an MRI rather than X-ray decision tool
Plantar Fasciitis
First-step morning heel pain improves with walking; stretching and orthotics are first-line before considering injections.
- Misses the first-step morning pain pattern characteristic of plantar fasciitis
- Underestimates the role of stretching and orthotics as first-line therapy before injections
Prepatellar Bursitis
Bursal swelling sits anterior to the patella, outside the joint; septic bursitis management differs from the urgency of septic arthritis.
- Confuses prepatellar bursal swelling with intra-articular joint effusion
- Conflates management of septic bursitis with the more urgent management of septic arthritis
Patellofemoral Pain Syndrome
Theater sign — pain with prolonged sitting — and activity-specific aggravation respond to quadriceps strengthening, not immobilization.
- Recommends rest/immobilization instead of quadriceps strengthening for patellofemoral syndrome
- Misses the theater sign and activity-specific aggravating factors of patellofemoral syndrome
Psoas Abscess
Hip flexion posture and positive psoas sign with fever; S. aureus causes primary disease, drainage is required alongside antibiotics.
- Fails to distinguish S. aureus (primary) from enteric/TB organisms (secondary) in psoas abscess
- Omits the necessity of drainage alongside antibiotics for psoas abscess management
Radial Head Subluxation (Nursemaid's Elbow)
Longitudinal traction in young children pulls the radial head through the annular ligament; hyperpronation is an effective reduction technique.
- Confuses the traction mechanism of nursemaid's elbow with a FOOSH injury
- Underestimates hyperpronation as an effective and often superior reduction technique
Slipped Capital Femoral Epiphysis (SCFE)
Obese adolescents with limited internal rotation and knee pain need both AP and frog-leg lateral X-rays; surgical pinning is urgent.
- Misses SCFE as the cause of referred knee pain in an obese adolescent
- Relies solely on AP X-ray and misses the need for frog-leg lateral view in SCFE
Burns and Rule of 9s
Blistering indicates second-degree burns; Parkland formula delivers half the calculated fluid in the first 8 hours.
- Misattributes blistering to third-degree rather than second-degree burns
- Overestimates adult head BSA or fails to adjust Rule of 9s for pediatric patients
Ichthyosis Vulgaris
Filaggrin loss causes retention hyperkeratosis with fish-scale skin; flexural sparing is a hallmark distinguishing feature.
- Confuses retention hyperkeratosis with proliferative hyperkeratosis as the mechanism of ichthyosis vulgaris
- Misses that flexural sparing is a hallmark feature of ichthyosis vulgaris
Skin Appendages and Hair Disorders
Alopecia areata is patchy and autoimmune; telogen effluvium follows a stressor by 2–3 months; finasteride inhibits 5-alpha reductase.
- Confuses the patchy distribution of alopecia areata with the patterned thinning of androgenetic alopecia
- Confuses finasteride's mechanism (5-alpha reductase inhibition) with androgen receptor blockade
Skin Lesion Terminology
Vesicle vs bulla is size-based; erosion heals without scar; ulcer extends to dermis and scars.
- Confuses the vesicle/bulla distinction as content-based rather than size-based
- Confuses plaque with a large papule, missing the flat-topped, coalescing nature of plaques
Atopic Dermatitis (Eczema)
Filaggrin mutation drives barrier defect; distribution shifts from extensor/facial in infants to flexural in older children.
- Misses the age-dependent shift in atopic dermatitis distribution from extensor/facial in infants to flexural in older patients
- Confuses atopic dermatitis (Th2-mediated) with Th1-mediated hypersensitivity reactions
Psoriasis
Th17/IL-23 axis, Auspitz sign histology, DIP involvement with seronegative arthritis, and a biologic-friendly treatment ladder.
- Misunderstands the histologic basis of the Auspitz sign in psoriasis
- Confuses psoriasis as a Th1 disease rather than recognizing the central Th17/IL-23 axis
Seborrheic and Contact Dermatitis
Malassezia drives seborrheic dermatitis; allergic contact is Type IV requiring prior sensitization; irritant contact needs none.
- Confuses the causative organism of seborrheic dermatitis as bacterial rather than Malassezia yeast
- Confuses allergic contact dermatitis (Type IV hypersensitivity) with Type I IgE-mediated reactions
Acne and Rosacea
Open comedone color reflects oxidized lipids, not dirt; isotretinoin requires iPLEDGE monitoring; rosacea lacks comedones entirely.
- Misattributes the black color of open comedones to dirt rather than oxidized melanin/lipids
- Confuses rosacea with acne vulgaris by expecting comedones, which are absent in rosacea
Pemphigus Vulgaris vs Bullous Pemphigoid
Intraepidermal split and flaccid bullae define pemphigus vulgaris; subepidermal split and tense bullae define bullous pemphigoid.
- Confuses the split level in pemphigus vulgaris (intraepidermal) with bullous pemphigoid (subepidermal)
- Confuses the tense bullae of bullous pemphigoid with the flaccid, fragile bullae of pemphigus vulgaris
Dermatitis Herpetiformis
Granular IgA at dermal papillae, obligate celiac link, gluten-free diet plus dapsone — but check G6PD first.
- Confuses the granular IgA deposits of dermatitis herpetiformis with the linear IgG deposits of bullous pemphigoid
- Misses the obligate association between dermatitis herpetiformis and celiac disease
Erythema Multiforme, Stevens-Johnson, TEN
EM is a distinct entity from SJS/TEN; BSA epidermal detachment (<10% vs >30%) separates SJS from TEN, not mucosal involvement alone.
- Incorrectly places EM on the same disease spectrum as SJS/TEN rather than recognizing them as distinct entities with different triggers
- Confuses the SJS/TEN distinction as mucosal vs. non-mucosal rather than the BSA epidermal detachment cutoffs
Bacterial Skin Infections
Non-bullous impetigo implicates Strep; erysipelas has sharp borders and upper dermis involvement; Group A Strep causes monomicrobial necrotizing fasciitis.
- Confuses impetigo as a purely staph infection, missing strep as a classic cause of non-bullous impetigo
- Confuses erysipelas with cellulitis, missing the key distinction of depth and border demarcation
Fungal and Parasitic Skin Infections
Dermatophytes show hyphae on KOH; Candida shows pseudohyphae plus budding yeast; scabies spares the adult face; molluscum is a poxvirus.
- Confuses KOH findings of dermatophytes (hyphae/arthroconidia) with Candida (pseudohyphae + budding yeast)
- Misses the characteristic distribution of scabies burrows in web spaces and flexural areas, sparing the adult face
Basal Cell and Squamous Cell Carcinoma
BCC rarely metastasizes via Hedgehog/PTCH1 pathway; SCC has higher metastatic potential and arises from actinic keratosis.
- Overestimates metastatic risk of BCC, failing to distinguish it from SCC's higher metastatic potential
- Confuses BCC's Hedgehog/PTCH1 pathway with melanoma's BRAF/RAS pathway
Melanoma
Breslow thickness is the primary prognostic factor; shave biopsy is contraindicated; BRAF V600E targeted therapy does not apply to acral/mucosal subtypes.
- Confuses Clark level with Breslow thickness as the primary prognostic depth measurement in melanoma
- Selects shave biopsy for suspected melanoma, which compromises Breslow depth assessment
Pigmentation Disorders
Vitiligo destroys melanocytes autoimmunely; albinism is a tyrosinase defect with normal melanocyte number; melasma needs UV and estrogen control.
- Confuses albinism (tyrosinase defect with normal melanocyte count) with vitiligo (melanocyte destruction/absence)
- Attributes vitiligo to an enzyme defect rather than autoimmune melanocyte destruction
Hidradenitis, Pyoderma Gangrenosum, Erythema Nodosum
Pyoderma gangrenosum worsens with debridement (pathergy); erythema nodosum is pretibial panniculitis; hidradenitis involves apocrine-bearing skin.
- Recommends debridement for pyoderma gangrenosum, ignoring pathergy and the need for immunosuppression
- Misplaces erythema nodosum lesions away from the classic pretibial location
NSAIDs and Acetaminophen
Aspirin irreversibly inhibits COX; COX-2 selectivity preserves renal toxicity; NAPQI accumulation from glutathione depletion drives acetaminophen hepatotoxicity.
- Confuses aspirin's irreversible COX inhibition with the reversible inhibition of other NSAIDs
- Assumes COX-2 selectivity confers renal protection, when renal toxicity risk is preserved
Corticosteroids (Systemic and Topical)
Genomic anti-inflammatory mechanism, HPA suppression with abrupt withdrawal, and low-potency agents required on facial skin.
- Confuses corticosteroid genomic mechanism with direct receptor antagonism at the cell surface
- Underestimates the danger of abrupt steroid withdrawal, missing HPA suppression and adrenal crisis risk
DMARDs and Biologics
Folate reduces MTX toxicity without blunting efficacy; TB screening is mandatory before TNF inhibitors; hydroxychloroquine toxicity targets the retina.
- Avoids folate supplementation with MTX fearing loss of efficacy, when folate reduces toxicity without blunting therapeutic effect
- Misidentifies hydroxychloroquine's major toxicity as hepatic rather than retinal (bull's-eye maculopathy)
Gout Pharmacology
Allopurinol is deferred until flares resolve; probenecid worsens uric acid stones; colchicine disrupts microtubules without lowering urate.
- Initiates allopurinol during an acute gout flare, when it should be deferred until the attack resolves
- Prescribes probenecid to a patient with uric acid kidney stones, when increased urinary urate worsens stone risk
Osteoporosis Pharmacology
Bisphosphonates inhibit osteoclasts; denosumab discontinuation causes rebound fractures; teriparatide is anabolic with a duration limit.
- Confuses osteonecrosis of the jaw as a generic bisphosphonate effect rather than a site-specific, procedure-triggered complication
- Confuses bisphosphonate mechanism as anabolic (osteoblast stimulation) rather than anti-resorptive (osteoclast inhibition)
Retinoids
Isotretinoin teratogenicity spans the entire treatment period; ATRA treats APL; pseudotumor cerebri and hypertriglyceridemia are confirmed systemic toxicities.
- Confuses isotretinoin teratogenic window as limited to first trimester rather than the entire treatment period
- Overstates isotretinoin-IBD causality while potentially underweighting confirmed toxicities like pseudotumor cerebri and hypertriglyceridemia
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