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USMLE Step 2 (Fach) / Muskuloskeletal/Rheumatology (Lektion)

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• Secondary malignancies of the bone (bone metastasis) Etiology- Primary malignancies: most commonly lung, breast, and prostate cancer (together comprising 80% of cases) Epidemiology:- Bone metastases comprise 70% of all malignant bone tumors- Bones are the third most common site of metastases, after the lung and the liver. Localization: most commonly spine (∼ 40%) and pelvis (∼ 20%) Classification: - Osteoblastic metastasis: e.g., prostate cancer, small cell lung cancer- Osteolytic metastasis: e.g., thyroid cancer, kidney cancer, melanoma, non-small cell lung cancer, multiple myeloma- Mixed metastasis (e.g., breast cancer, gastrointestinal cancer) Clinical findings:- Often no or few symptoms (incidental finding during routine staging of the primary tumor)- Local pain and swelling- Pathologic fractures- Spinal cord compression and/or radicular symptoms Diagnostics:- Imaging is generally only performed in patients with primary malignancies who have clinical signs or laboratory findings (e.g., elevated alkaline phosphatase, hypercalcemia) indicating metastatic bone disease- Biopsy is performed to confirm the diagnosis when imaging is insufficient or the patient has no known history of cancer- Laboratory: ↑ calcium- For suspected spinal lesions: Contrast-enhanced MRI - For suspected extremity lesions: Conventional X-ray, followed by CT or MRI if pathological fracture is identified or suspected for operative planning- Whole-body skeletal imaging: indicated if a metastatic lesion is identified to detect additional, asymptomatic sites of metastasis Treatment:- Pain management- Systemic therapy: Chemotherapy- Osteoclast inhibitors (e.g., bisphosphonates): inhibit bone resorption- Localized tumor radiation- Surgery→ If pathologic fractures have occurred or are likely: stabilize and restore function→ If spinal instability or spinal cord compression has occured or is likely: immediate decompression and stabilization
• Giant-cell tumor of bone (osteoclastoma) Peak incidence: 20-40 years Localization: epiphyseal/metaphyseal region of the long bones(predominantly affects the bones close to the knee) Clinical findings:- Local pain and swelling- Limited range of motion- Pathological fractures DiagnosticsX-ray: multicystic osteolytic lesions Histopathology: multinucleated giant cells Treatment: curettage and bone grafting, or en bloc resection to minimize reccurence rate Prognosis: risk of malignant degeneration increases with age; may metastasize to the lungs
• Osteochondroma Definition: formation of mature bone outgrowth on the surface of long bones, adjacent to growth plates with a cartilaginous cap Epidemiology:- Most common primary benign bone tumor- Peak incidence: 10-20 years- Sex: ♂ > ♀ Localization: metaphysis of long bones Clinical findings: usually asymptomatic, but can be painful and palpable near the ends of long bones Conventional x-ray: pedunculated or sessile lesion on the surface of the metaphysis of long bones Treatment: excision of tumor in symptomatic cases Complications: ∼ 1% transform into chondrosarcoma.
• Chondrosarcoma Malignant tumor arising from mesenchymal cells that produce cartilage Etiology:- Primary chondrosarcoma: unknown- Secondary chondrosarcoma: e.g., osteochondroma, Paget's disease of bone, radiation Epidemiology:- Age: usually > 50 years- Sex: ♂ > ♀ Clinical findings:- Deep, dull pain (worsens at night, insidious progression over months to years)- Local swelling- Pathological fractures- Neurovascular disturbances and/or limited range of motion Localization: mainly pelvis, ribs, proximal femur, and proximal humerus Diagnostics:- Conventional x-ray or CT→ Osteolysis with moth-eaten appearance→ Calcifications (rings and arcs calcification, popcorn calcification)→ Endosteal scalloping and cortical breach with infiltration of soft tissue- MRI: rim-like contrast enhancement- Biopsy: Lobulated appearance (hyaline cartilage nodules with peripheral calcification)  Treatment:- Surgery (definitive resection)- Chemotherapy and radiation therapy, possibly as adjuvant therapy or as palliative treatment
• Thoracic outlet syndrome An umbrella term for conditions involving the compression of neurovascular structures (e.g., the brachial plexus or the subclavian artery or vein) as they pass from the lower neck to the armpit. Etiology: Compression of subclavian vessels and the lower trunk - Physical trauma (e.g. hyperextension neck injuries) - Repetitive motion of the abducted and externally rotated shoulder (e.g. tennis, baseball, swimming, repetitive throwing, carrying heavy objects overhead) - Structural abnormalities→ Bones: anomalous cervical rib , collarbone fracture, exostoses of the first rib or collarbone → Soft tissue: hypertrophic muscles in athletes and weight lifters, poor posture and obesity, hematoma, tumors (e.g., Pancoast tumor) Clinical features:- Compression of the subclavian artery→ Mild arm ache and fatigue→ Pulselessness, pain, pallor, paresthesia and coldness in the affected arm (5 Ps)  → ↓ Blood pressure of > 20 mm Hg in the affected arm compared with the contralateral arm - Compression of the subclavian vein→ Swelling→ Venous distention→ Diffuse hand or arm pain→ Heaviness→ Risk of thrombosis of the arm (Paget-Schroetter disease) - Compression of parts of the brachial plexus→ Sensory loss or paresthesia → Pain in the neck and arm→ Atrophy of hand muscles (Gilliatt-Sumner hand) Treatment - In mild cases: physical therapy, weight reduction, NSAIDs, thrombolytics with continued anticoagulation in the case of venous thrombosis- In cases of acute vascular insufficiency or progressive neurologic dysfunction, or if conservative treatment fails: thoracic outlet decompression surgery
• Physiological knee alignment ≤ 2 years: Genu varum deformity (bow legs) - Typically corrects as the infant learns to walk and bear more weight on the lower extremities. 18-24 months: Neutral ≥ 2 years: Turns into a genu valgum deformity (knock-knees) Resolves by age 5.  Treatment: Regular follow-up examinations are recommended to measure the intercondylar distance and to document the expected spontaneous resolution.
• Congenital clubfoot Clinical features:- Bilateral in 30-50% of cases- Rigid positioning- Medial/upward deviation of forefoot & hindfoot- Hyperplantar flexion of foot Treatment: - Serial manipulation & casting- Surgery for refractory cases
• Metatarsus adductus Epidemiology:- First-born infants; likely due to the crowded positioning in a smaller, primigravid uterus Clinical features:- Bilateral- Flexible positioning- Medial deviation of forefoot- Neutral position of hindfoot Treatment: Reassurance
• Ewing sarcoma Highly malignant bone tumor arising from neuroectodermal cells; associated with various chromosomal translocations of the EWSR1 gene (chromosome 22). Epidemiology:- Second most common pediatric bone malignancy after osteosarcoma- White, adolescent boys Clinical features:- Chronic, localized pain & swelling (progressive, worsens at night)- Long bone diaphyses & axial skeleton (eg, pelvis)- ± Systemic findings (eg, fever, leukocytosis) Diagnostics:- Conventional x-ray: → Central lytic lesion→ "Onion skinning" (lamellated periosteal reaction)→ "Moth-eaten" appearance- Laboratory findings: ↑ ESR, ↑ LDH, leukocytosis- Biopsy: Anaplastic small-blue-round-cell malignancy- Chromosomal translocation t(11;22)(q24;q12) Treatment:- Surgery (definitive resection) plus neoadjuvant and adjuvant polychemotherapy- Additionally: neoadjuvant and/or adjuvant radiation therapy Prognosis: Five-year survival rate of ∼ 70%
• Osteoporosis A skeletal condition in which the loss of bone mineral density leads to decreased bone strength and an increased susceptibility to fractures. Epidemiology:- Sex: ♀ > ♂ (∼ 4:1)- Age of onset: 50-70 years- Demographics: higher incidence in individuals of Asian, Hispanic and northern European ancestry than in black populations Etiology:- Postmenopausal women- Drug-induced/iatrogenic: especially after systemic long-term therapy with corticosteroids (e.g., in patients with autoimmune disease) → Other: Long-term therapy with proton-pump inhibitors, anti-epileptic drugs, aromatase inhibitors- Endocrine/metabolic: hypercortisolism, hypogonadism, hyperthyroidism, hyperparathyroidism, renal disease- Immobilization- Alcohol abuse Risk factors:- Cigarette smoking- Family history of osteoporosis- Malnutrition, malabsorption- Low body weight Clinical features:- Mostly asymptomatic- Pathological fractures: spontaneous fracture following mild physical exertion or minor trauma (e.g., lifting something, bending over, or sneezing/coughing) → Localizations: vertebral (most common) > femoral neck > distal radius (Colles) fracture, fractures of the long bones (e.g., humerus)- Decreased height (loss of 2-3 cm with each fracture)- Thoracic hyperkyphosis → stooped posture with a “dowager's hump” Diagnostics: - DXA (dual-energy X-ray absorptiometry): Calculates bone mineral density (BMD) in g/cm2→ General recommendation for women ≥ 65 years and men ≥ 70 years→ In younger individuals if additional risk factors are present (e.g., prolonged glucocorticoid use, low BMI (< 21 kg/m2) or weight < 127 lb, alcohol use, smoker, amenorrhea)→ Osteoporosis: T-score ≤ -2.5 SD→ Osteopenia: T-score of -1 to -2.5 SD- Plain radiography: If osteoporosis is diagnosed: radiographic assessment of the whole skeletal system is recommended- Global demineralization is apparent only after >30% of bone denisty is lost- Clinical chemistry: usually normal Treatment:- Lifestyle measures: Avoid alcohol and nicotine, sufficient intake of calcium and vitamin D, physical activity, avoid or minimize glucocorticoids- 1st-line treatment: bisphosphonates (alendronate, risedronate); inhibit osteoclasts and therefore bone resorption- Teriparatide (parathyroid hormone analog): alternative for severe osteoporosis (T-score ≤ -3.5) or for patients with contraindications to bisphosphonates- Raloxifene (selective estrogen receptor modulator, SERM) for patients with contraindications to bisphosphonates or those who also require breast cancer prophylaxis (but increases the risk of thromboembolism) - Denosumab (monoclonal antibody against RANKL) : for patients with impaired renal function, or no success with bisphosphonates
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• Legg-Calvé-Perthes disease Idiopathic, avascular necrosis of the femoral head. Epidemiology:- Sex: ♂ > ♀ (4:1)- Peak incidence: 4-10 years Clinical features:- Antalgic gait (on weight-bearing leg)- Pain in the hip or the upper leg, sometimes projecting to the knee- Insidious onset, pain may fluctuate depending on physical activity- Often exacerbated by internal rotation- FABER (Flexion, ABduction, and External Rotation) test elicits pain.- Groin tender on palpation- Restricted range of movement is always present, especially regarding internal rotation and abduction.- Hinge abduction: refers to the lateral femoral head bumping into the ventrolateral acetabulum when the leg is abducted, possibly involving pain, a palpable clunk, and restriction in the range of movement.- Contralateral involvement in ∼ 15% of cases Lateral pillar classification Diagnostics:- X-ray (anterior-posterior and frog leg positions)→ Frequently unremarkable during the first 3-6 months!→ Joint space widening, increased lucency, flattening of the epiphysis- MRI: Indicated in case of unremarkable initial imaging Treatment:- Conservative treatment: Limited weight bearing, physical therapy→ Young children (< 6 years of age)→ Lateral pillar A classification→ Consider casting and bracing before surgery if femoral head deformity develops or range of motion worsens- Surgery: femoral osteotomy→ Older children (> 8 years of age)→ Lateral pillar B/C classification→ Extensive damage to the femoral head Complications: Early osteoarthritis of the hip joint Prognosis:- Age at onset is the most important prognostic factor: the younger the patient, the better the prognosis!- Girls with LCPD have a less favorable prognosis than boys.
• Femoral nerve injury Nerve roots: L2-L4 Etiology:- Direct injury (trauma)- Prolonged pressure on the nerve: psoas hematoma, aortic or iliac aneurysms or tumors- Iatrogenic: pelvic, abdominal, or spinal surgery; femoral line placement. Sensory deficit:- Anterior cutaneous branches: anteromedial thigh- Saphenous nerve lesion: medial lower leg, medial edge of the foot Motor deficit:- Paralysis of iliopsoas, pectineus, rectus femoris, and sartorius muscles (↓ hip flexion)- Paralysis of quadriceps femoris muscle (↓ knee extension, ↓ patellartendon reflex)
• Sciatic nerve injury Nerve roots: L4-S3 Etiology:- Iatrogenic (misplaced intragluteal injection!)- Direct trauma (gun and/or stab wounds)- Hip dislocation- Total hip arthroplasty Sensory deficit: lower leg and foot Motor deficit:- Paralysis of hamstring muscles → impaired knee flexion- Motor deficits of tibial nerve injury and common peroneal nerve injury
• Marfan syndrome Etiology:- Mutation of fibrillin-1 gene (FBN1) on chromosome 15 → defective connective tissue microfibrils → defective elastin- Autosomal dominant inheritance pattern with variable penetrance Clinical features:- Features of aortic disease: Aortic necrosis (cystic medial degeneration), aortic regurgitation, aortic aneurysm, aortic dissection (typically of the thoracic aorta)- Mitral valve prolapse- Berry aneurysms, which can rupture → subarachnoid hemorrhage- Tall stature with rapid linear growth and long extremities- Joint hypermobility- High-arched palate- Arachnodactyly (achromachia)- Pectus deformity (pectus carinatum or pectus excavatum)- Pes planus (flat foot) or hindfoot valgus- Spinal deformities (scoliosis, hyperkyphosis)- Loss of skin elasticity/striae (stretch marks)- Visual impairment: ectopia lentis (lens dislocation) → lens subluxation superiorly and temporally- Severe myopia Diagnostics: Clinical- Echocardiography (cardiovascular manifestations)- Slit-lamp examination (to exclude lens abnormalities)- Imaging: skeletal x-rays and MRI (dural ectasia in Marfan syndrome)
• Ehlers-Danlos syndrome Etiology:- Various mutations in genes that control the synthesis and processing of collagen (e.g., defect in lysine-hydroxylysine cross-linking of tropocollagen → unstable collagen fibrils)- EDS type (Villefranche classification): Inheritance patterns and type of collagen affected vary (can be autosomal dominant or recessive)→ Mutation of type V collagen → Classic EDS (types I and II) in which joint and skin manifestations predominate→ Hypermobility EDS (type III) in which joint manifestations predominate→ Mutation of type III collagen → Vascular EDS (type IV) in which cardiovascular manifestations predominate Clinical features:- Heart valve defects (particularly mitral valve prolapse)- Features of aneurysms/dissections of the iliac, splenic, renal arterties, or the aorta- Berry/saccular aneurysms of the cerebral arteries → features of subarachnoid hemorrhage- Joint hypermobility with tendency to dislocate- Skeletal abnormalitis (e.g., scoliosis) - Tendency to bruise easily- Skin hyperextensibility- Frequent skin lacerations and poor skin healing (e.g., following surgery)- Hernias- Features of organ rupture (e.g., shock, local pain), especially in vascular EDS
• Patellar dislocation Epidemiology:- Sex: ♀ > ♂- The first episode of patellar dislocation typically happens before the age of 20- 50% of patients will have recurrent patellar dislocations after the first episode Etiology: - Recurrent patellar dislocation. The following biomechanical defects predispose an individual to recurrent patellar dislocation:→ Patellofemoral dysplasia (trochlear dysplasia and patellar dysplasia)→ A large Q angle; causes include: Genu valgum ("knock-knee”) deformity, injury to the medial patellofemoral ligament, weakness of vastus medialis→ Patella alta (high-riding patella)→ Hyperlaxity of joints: connective tissue conditions (Ehlers-Danlos syndrome, Marfan syndrome), slack ligaments (♀ > ♂)- Traumatic patellar dislocation Clinical features.- Severe pain- Knee joint effusion- Restricted range of motion in the knee (usually a fixed flexion deformity)- The patella is almost always dislocated laterally.- Recurrent patellar dislocation→ The patella often relocates spontaneously→ Permanent feeling of instability→ Positive apprehension test Diagnostics:- X-ray: to detect the underlying cause and additional injuries- MRI and arthroscopy: to examine the ligaments and cartilaginous structures- Knee joint aspiration: indicated in the case of severe joint effusion→ Injury to ligamentous structures of the knee (e.g., the medial patellar retinaculum) → hemarthrosis→ A fracture which extends intraarticularly (e.g., an avulsion fracture of the femoral condyle) → lipohemarthrosis Treatment:- Conservative therapy: indicated if no osteochondral fragment is present → Patellar reduction by gently extending the knee while applying a caudally and medially directed force on the lateral edge of the patella→ Reduction should be followed by immobilization of the knee in extension for three weeks.→ Physiotherapy to strengthen the quadriceps femoris muscle: to prevent recurrent disclocation- Surgical therapy: generally indicated for complicated cases with associated fractures→ Arthroscopy 
• Temporomandibular joint dysfunction Pain and dysfunction of the temporomandibular joint (TMJ) due to musculoskeletal, psychological and/or neuromuscular factors Peak incidence: 20-40 years Clinical features- Pain can spread to the ear, temporal regions, periorbital regions, or the mandible- Pain often episodic and sharp- Pain worsened by jaw motion (chewing)- Pain on palpation of the TMJ- Ear discomfort- Headache- Cracking or grinding of the TMJ- Limited jaw opening (occasionally painful)- Nocturnal teeth grinding (bruxism) Diagnosis: clinical diagnosis Treatment- Indications: Pain with palpation, jaw movement, or biting/chewing, masticatory muscle spasms- Behavioral therapy to avoid triggers- Pain relief (NSAIDs, tricyclic antidepressants, benzodiazepines, and/or muscle relaxants)- Occlusal splints for bruxismSymptoms resolve spontaneously in approx. 40% of patients!
• Serum sickness Serum sickness is classically a type III hypersensitivity reaction appearing as a complication of antitoxin or antivenom administration.Serum sickness-like reaction is much more common than actual serum sickness. Serum sickness-like reactions are caused by medications or infections. Etiology:- Antivenom or antitoxin containing animal proteins or serum (→ “serum” sickness) - Medications, most frequently antibiotics (e.g., penicillin, amoxicillin, cefaclor, trimethoprim-sulfamethoxazole)- Infections: Hepatitis B virus Clinical features:- Fever- Rash (urticarial or purpuric)- Arthralgias, myalgia- Headache, blurred vision- Abdominal pain, diarrhea, nausea/vomiting- Lymphadenopathy Course: - Symptoms appear 1-2 weeks following initial exposure.- They resolve within a few weeks of discontinuation. Treatment: stop the offending agent
• Calcaneal apophysitis (Sever disease) Risk factors:- Running/jumping sports- Growth spurts- Athletic cleat use or footwear without heel padding Clinical features:- Heel pain (50% bilateral)- Pain with calcaneal palpation or compression- Decreased gastrocnemius/soleus flexibility Treatment:- NSAIDs, ice- Activity limitation
• Greater trochanteric pain syndrome (trochanteric bursitis) Risk factors:- Age ≥ 50- Women > men- Obesity- Low back & lower extremity disorders (e.g., scoliosis, osteoarthritis, plantar fasciitis) Clinical features:- Chronic lateral hip pain- Pain worse with hip flexion or lying on affected side Diagnosis:- Focal tenderness over trochanter- X-ray to rule out hip joint pathology- Ultrasound: degeneration of tendons, tendinosis Treatment:- Exercise, physical activity, activity modification- NSAIDs- Corticosteroid injection
• SLE and pregnancy Characteristics:- Fertility is not affected.- Pregnancy may cause flares in disease activity.- ↑ Risk of preterm birth, hypertensive complications (preeclampsia), intrauterine growth restriction, fetal AV block, and miscarriage Risk assessment:- Cardiac, lung, and kidney screening- Maternal antibodies: anti-Ro/SSA and anti-La/SSB- Anticardiolipin antibodies and lupus anticoagulant (see antiphospholipid syndrome) Management:- Pregnancy planning and counseling- Prednisolone, azathioprine; cyclosporin, tacrolimus, and hydroxychloroquine are considered safer drug options during preconception, pregnancy, and breastfeeding.- Some immunosuppressive medications used to treat SLE (e.g. mycophenolate and cyclophosphamide) have severe teratogenic and other adverse fetal effects.- Low-dose aspirin is recommended in all pregnant women from 12 weeks gestation Neonatal lupus syndrome:- Associated with the transfer of maternal antibodies (anti-Ro/SSA and anti-La/SSB)- Periorbital or diffuse rash (often presents in the first weeks after birth)- Cytopenia- Hepatitis, elevated liver enzymes- First- to third-degree congenital AV block

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