A 45-year-old woman comes to the office due to a long history of joint pain, swelling, and stiffness.  She recently immigrated to the United States and had little access to medical care in her original country.  On physical examination, her proximal interphalangeal and metacarpophalangeal joints are tender and swollen bilaterally, and her fingers appear significantly deformed.  Subcutaneous nodules are palpated near the elbow.  Laboratory studies are obtained to confirm the diagnosis.  This patient’s serum is most likely to contain IgM antibodies against which of the following substances?

A 28-year-old man comes to the office with a 2-month history of dull low back pain and morning stiffness.  The pain had an insidious onset, and the patient does not recall any back trauma.  He attempted treatment with acetaminophen and spinal manipulation, which did not provide significant relief.  The patient had been a back sleeper, but now must lie on his side to fall asleep easily.  Past medical history is unremarkable.  Vital signs are normal.  Physical examination shows limited anterior flexion of the spine.  There is no swelling or warmth of any peripheral joints.  X-rays reveal narrowing of the sacroiliac joints.  Which of the following is most strongly associated with this patient’s condition?

A 34-year-old man comes to the physician due to painful urination.  Physical examination shows a watery penile discharge.  Urethral swabs obtained from the patient are negative for gonococcal infection.  He is treated appropriately and his symptoms resolve.  Two weeks later, he develops acute conjunctivitis, right knee pain, and vesicular rash on his palms and soles.  This patient’s condition is most likely associated with which of the following?

A 42-year-old woman comes to the emergency department due to worsening jaw pain over the past week.  She is unable to chew solid foods on the left side because of severe throbbing pain.  The patient has had several “tooth infections” over the last year despite meticulous oral hygiene.  Physical examination shows facial edema over the left mandible.  Multiple teeth have decay and gingival recession, and gentle tapping of the left second molar elicits pain.  This patient’s current disease process is most likely to develop secondary to which of the following underlying conditions?

A 47-year-old woman comes to the office due to progressive exertional dyspnea and fatigue.  She also reports painful episodes of bluish discoloration of the fingers and toes that are triggered by cold exposure and improve with rewarming.  Medical history is significant for severe gastroesophageal reflux disease.  Physical examination shows skin tightening over the fingers.  The oral aperture is small, and scattered telangiectasias are present over the lips.  Cardiac examination demonstrates an increased intensity of S2 over the upper left sternal border.  Lungs are clear to auscultation with normal air movement and no crackles.  The abdomen is soft with mild hepatomegaly.  There is bilateral lower extremity pitting edema.  Chest x-ray reveals no abnormalities.  Results of office spirometry are as follows:

Which of the following is the most likely cause of this patient’s dyspnea?

A 62-year-old woman is brought to the emergency department due to progressive weakness and dyspnea.  The patient is visiting her niece, who says the patient forgot to bring her regular medications and has not been taking them for the past week.  The patient began feeling weak and fatigued 3 days ago and has had shortness of breath since yesterday.  Temperature is 37 C (98.6 F), blood pressure is 122/88 mm Hg, pulse is 90/min, and respirations are 24/min and shallow.  On physical examination, the patient appears dyspneic with drooping at the eyelids and corners of the mouth.  Her speech has a nasal quality.  Arterial blood gas obtained on room air shows pH 7.32; PaCO₂ is 52 mm Hg, PaO₂ is 72 mm Hg, and HCO₃ is 26 mEq/L.  Bedside spirometry demonstrates decreased forced vital capacity.  A pathologic process involving which of the following structures is the most likely cause of this patient’s shortness of breath?

A 23-year-old woman comes to the office due to sharp, right-sided chest pain, fatigue, and fever for the past week.  The chest pain is worsened with deep breathing.  She has had no associated expectoration or shortness of breath.  For the past 6 months, the patient also has had intermittent joint pains, predominantly in the knees and hands.  She is sexually active with one male partner and uses an intrauterine device for contraception.  Temperature is 38.3 C (100.9 F), blood pressure is 120/70 mm Hg, pulse is 89/min, and respirations are 18/min.  BMI is 24 kg/m².  Examination shows mild erythema over the cheeks and a scratching sound over the right lower lung with breathing.  Heart sounds are normal.  There is no joint swelling.  Which of the following tests is most useful in confirming the diagnosis?

A 54-year-old previously healthy man comes to the office due to progressive fatigue and weakness for the past 2 months.  His weakness predominantly involves the lower extremities, causing him to have difficulty rising from a chair.  The patient also has a persistent cough and unintentional 7-kg (15.4-lb) weight loss during the same period.  He has a 30-pack-year smoking history and drinks alcohol occasionally.  Physical examination shows bilaterally decreased strength in the proximal muscles of the lower extremities with normal bulk and tone.  Quadriceps tendon reflexes are diminished bilaterally.  Chest x-ray reveals a hilar mass, biopsy of which demonstrates small cells that stain positive for chromogranin and synaptophysin.  Which of the following is the most likely cause of this patient’s muscle weakness?

A 31-year-old woman is brought to the hospital due to respiratory difficulty.  She has had trouble performing her daily activities for the past few weeks due to fatigue.  In particular, her arms seem to “just drop” when she combs her hair.  The patient’s symptoms are generally better in the morning and worsen throughout the day.  She does not use tobacco, alcohol, or illicit drugs.  Examination shows diplopia.  Chest auscultation shows normal heart and breath sounds.  Deep tendon reflexes are normal.  Babinski sign is absent.  The results of arterial blood gas analysis are as follows:

Which of the following is most likely abnormal in this patient?

A 61-year-old woman comes to the clinic due to vision problems for the last 6 months.  The patient says her eyes get tired easily, especially in the late afternoon and evening.  She has smoked a pack of cigarettes daily for the past 35 years and does not use alcohol or illicit drugs.  On physical examination, there is weakness of the extraocular muscles.  Pupillary reflex, deep tendon reflexes, and sensation are normal.  A contrast-enhanced CT scan of the chest is shown in the exhibit.  Which of the following is the most likely mechanism underlying this patient’s symptoms?

A 25-year-old woman comes to the hospital due to worsening dyspnea.  The patient was previously healthy; 2 months ago, she delivered a healthy baby boy at 38 weeks gestation.  Her arterial blood gas analysis shows evidence of hypoventilation.  During further evaluation, she is asked to take several deep breaths, and the following physiologic information is obtained:

Which of the following locations is the most likely site of this patient’s disease?

A 62-year-old woman has double vision, especially when reading at bedtime.  The problem first started several months ago and was intermittent but has worsened over the last 2 weeks and now bothers her constantly.  The patient has also developed difficulty chewing and swallowing foods.  She usually feels better in the mornings.  She has no extremity weakness or sensory symptoms.  The patient has no other medical problems and takes no medications.  She does not use tobacco, alcohol, or illicit drugs.  Vital signs are normal.  BMI is 27 kg/m².  Examination shows bilateral ptosis; there is weakness of adduction of the right eye and abduction of the left eye.  Muscle strength is 4/5 in proximal muscles in the upper and lower extremities.  Deep tendon reflexes are 2+ throughout.

Item 1 of 2

Which of the following changes involving the postsynaptic muscle cell most likely explains this patient’s symptoms?

Item 2 of 2

The patient is started on appropriate treatment and reports significant symptom improvement.  However, she now has abdominal cramping, nausea, sweating, and diarrhea.  Which of the following agents can be used to effectively control these new symptoms?

A 56-year-old woman is brought to the emergency department due to several days of progressive dyspnea, productive cough, and fever.  Today, her son found her very short of breath and obtunded.  The patient has a history of hypertension, type 2 diabetes mellitus, and long-standing rheumatoid arthritis.  Examination reveals bilateral pneumonia and severe respiratory distress.  The patient is lethargic without focal neurologic deficits.  Urgent endotracheal intubation is performed for mechanical ventilation, and the patient is started on broad-spectrum antibiotics.  Repeat examination 2 hours later shows that she has developed areflexic, flaccid paralysis of all extremities.  Which of the following is the most likely cause of the neurologic deficits in this patient?

A 13-year-old boy is brought to the office due to right knee pain.  Several weeks ago, he developed mild anterior knee pain that has gradually worsened and now causes him to limp.  The pain has significantly limited his participation in basketball practice.  It is relieved by rest and can be reproduced when the patient straightens out his right knee while seated in a chair.  Further evaluation reveals an avulsion fracture affecting a developing secondary ossification center due to muscle overuse.  Which of the following structures is most likely involved in this patient’s disease process?

A 68-year-old man comes to the office due to difficulty performing normal day-to-day activities with his hands.  He has had pain in his finger joints, wrists, and knees for many years and has been taking over-the-counter analgesics.  The patient has been evaluated by doctors for “joint problems” in the past but declined their treatment recommendations.  He has smoked a pack of cigarettes daily for 30 years.  Vital signs are normal.  Examination findings of the patient’s hands are shown in the image below.

Which of the following pathogenic mechanisms is most likely responsible for this patient’s condition?

A 2-year-old boy is brought to the emergency department due to high fever and malaise for the past 4 days.  His parents say that he began limping yesterday and now refuses to walk.  The patient has had no recent travel or exposure to anyone with similar symptoms.  Temperature is 39.4 C (103 F).  Passive range of motion of the hips, knees, and ankles does not elicit pain.  There are no joint effusions.  The patient refuses to bear weight.  An intravenous radiotracer that localizes to areas of increased osteoblastic activity is administered, and several images are obtained to find areas with atypical activity.  Abnormally increased uptake of the radiotracer is most likely to be seen in which of the following areas?

A 59-year-old man comes to the office due to progressive weakness for the past several weeks.  The patient has had difficulty getting out of bed and climbing stairs in the morning, which improves gradually as he “warms up the muscles” with continued use.  He has also had to drink water more frequently due to dry mouth and has had episodic double vision.  The patient also reports difficulty achieving erections despite having a good libido.  Neurologic examination shows decreased strength of the hip flexors and diminished knee reflexes.  Repeat examination after lower extremity isometric exercise shows normalization of the muscle strength and deep tendon reflexes.  Which of the following conditions is most closely associated with this patient’s current disease process?

A 28-year-old man comes to the emergency department due to 12 hours of severe right knee pain and swelling. He has had no trauma. The patient drinks 1 or 2 cans of beer on weekends but does not use tobacco or illicit drugs. On physical examination, right knee effusion, erythema, and tenderness are present. Active and passive range of motion is markedly decreased. Other joints are normal. Arthrocentesis is performed, and synovial fluid analysis shows a white blood cell count of 110,000/mm3. Which of the following would provide the best treatment for this patient’s condition?

A 60-year-old man comes to the office due to a 4-month history of increasing midthoracic back pain, which is aggravated by coughing.  The patient has also had right thigh pain but no numbness or weakness in the legs and no bowel or bladder incontinence.  He has no other medical conditions.  Vital signs are within normal limits.  On examination, there is tenderness over the eighth and ninth thoracic vertebrae.  Neurologic examination is normal.  The prostate is normal in size and has no palpable nodules.  Imaging studies reveal enlarged vertebral bodies with cortical thickening.  Serum testing for which of the following would most likely help establish a diagnosis in this patient?

A 61-year-old woman who recently immigrated to the United States has a long history of “joint problems.”  She began to have pain in her hands at age 30, and her symptoms have been intermittent but progressive since then.  The symptoms were treated with nonsteroidal anti-inflammatory drugs when the pain was most severe.  The patient also has a history of hypertension and chronic anemia.  She does not smoke cigarettes or use illicit drugs.  Family history is insignificant.  On examination, there is gross deformity of multiple joints in both hands.  X-ray findings are shown in the image below.

The disease process responsible for the radiographic findings would most likely affect which of the following?

A 27-year-old man comes to the emergency department due to severe left knee pain and swelling for the past 2 days.  He has no recent injuries or significant medical conditions.  The patient drinks 3 or 4 cans of beer daily; he does not use tobacco or recreational drugs.  He works as a groundskeeper at a nearby golf course and had to take the last couple of days off because of the pain.  Temperature is 38.3 C (100.9 F), blood pressure is 115/70 mm Hg, and pulse is 92/min.  On examination, the left knee is swollen, erythematous, warm, and tender with restricted active and passive range of motion.  The remainder of the examination is unremarkable.  Which of the following is the best next step in management of this patient?

A 35-year-old woman comes to the office with symmetric swelling and pain of her proximal interphalangeal, wrist, and knee joints.  She reports that her 5-year-old son was seen by his pediatrician last week for a facial rash and fever.  The patient’s family history is significant for diabetes mellitus and gout in her father and rheumatoid arthritis in her mother.  Her serum rheumatoid factor is negative.  Conservative management with nonsteroidal anti-inflammatory drugs is recommended.  The patient returns for follow-up 4 weeks later and reports that she discontinued the medication after 2 weeks due to gastrointestinal upset.  However, her pain and swelling have decreased significantly.  Which of the following is the most likely diagnosis?

A 27-year-old man comes to the emergency department with progressive right knee swelling and pain.  He has no history of trauma to the area.  The patient has no other medical conditions and takes no medications.  X-rays reveal a large lytic and sclerotic lesion involving the proximal tibia, with extensive soft tissue swelling.  After additional confirmatory testing, the patient undergoes a right-sided, above-knee amputation.  Histologic examination of the resected mass is shown in the exhibit.  Which of the following is the most likely diagnosis?

A 48-year-old woman comes to the office due to difficulty swallowing dry foods such as crackers.  She has no pain during swallowing or heartburn.  The patient is a college professor and has to drink water frequently during lectures to keep her mouth moist.  She also reports a gritty sensation in her eyes, which is often worse in the evening, and occasional brief episodes of joint pain.  Medical history is significant for hypothyroidism, for which she takes levothyroxine.  Physical examination shows mild conjunctival erythema and cracking of the lips.  There is diffuse, nontender thyroid enlargement, which is unchanged from prior examination.  The remainder of the examination is normal.  Biopsy of the lip mucosa is most likely to reveal which of the following findings?

A 62-year-old woman comes to the office due to a 3-month history of progressive muscle weakness.  The patient has been having difficulty with activities such as getting out of the car and carrying groceries from the store.  She has also developed a rash on her face and hands.  The patient has a history of well-controlled hypertension and does not use tobacco, alcohol, or illicit drugs.  Vital signs are within normal limits.  Physical examination shows weakness of shoulder abduction and hip flexion.  Strength of the distal limb muscles and deep tendon reflexes are normal.  Skin examination findings are shown in the exhibit.  Which of the following is the most appropriate initial treatment for this patient’s current condition?

A 52-year-old woman comes to the office due to pain in the right knee for the past several months.  The pain is typically better in the morning but worsens by the end of the day.  There is no history of trauma to the joint.  Medical history is significant for hypertension, type 2 diabetes mellitus, and hypercholesterolemia.  The patient is a lifetime nonsmoker.  She works as an office clerk.  Family history is significant for stroke in her mother and gout in her father.  Temperature is 37.2 C (99 F), blood pressure is 145/95 mm Hg, and pulse is 90/min.  BMI is 37 kg/m².  Physical examination shows crepitation on flexion and extension of the right knee; range of motion is otherwise normal, and there is no swelling, warmth, or redness.  Which of the following pathologic processes is most likely occurring in this patient’s knee joint?

A 43-year-old woman comes to the office due to progressive fatigue and intermittent pain in the hands, feet, and knee joints.  The pain caused the patient to stop her daily yoga routine 2 months ago, and she has had difficulty performing daily household activities.  She has had no fever, rash, or oral ulcers but frequently drinks water or chews gum due to her mouth feeling dry.  The patient has no prior medical conditions and takes no medications or herbal supplements.  She does not use tobacco, alcohol, or recreational drugs.  Vital signs are within normal limits.  Physical examination shows no muscle tenderness or joint swelling.  The thyroid gland is normal to palpation.  There is nontender, diffuse swelling of the parotid glands.  Laboratory evaluation shows mild normocytic normochromic anemia and an elevated erythrocyte sedimentation rate.  A salivary gland biopsy image representative of this patient’s disease process is shown in the exhibit.  This patient is at greatest risk for developing which of the following conditions?

A 45-year-old woman suffers from recurrent nonpitting edema of the hands.  She often wears warm gloves indoors because her fingers turn blue when they are cold.  She also complains of retrosternal burning and regurgitation, especially when supine.  Which of the following antibodies is most likely to be found in this patient?

A 50-year-old man comes to the office for evaluation of a mass on his back.  He has had the mass for several years, and it has increased only slightly in size during that time.  The patient has 2 other similar lesions, one on his arm and the other on his leg.  The lesions are painless, and he has no other symptoms.  Vitals signs are normal.  Examination shows multiple subcutaneous, soft, freely mobile, and nontender masses.  The lesion on his back is shown in the image.

Histologic examination of the mass is most likely to show which of the following findings?

A 62-year-old woman comes to the office due to activity-related joint pain in the hands and periodic morning stiffness that lasts 10-15 minutes.  The pain is moderately severe and has begun to limit her activities.  The patient has attempted to treat the pain with acetaminophen, which provided only partial relief.  Past medical history is notable for hypertension and diabetes mellitus.  Physical examination shows firm nodules over the distal interphalangeal joints bilaterally as shown in the image below.

Which of the following is the most likely cause of this patient’s symptoms?

A 48-year-old woman comes to the office with a 4-month history of pain, stiffness, and swelling of her hands, feet, and knees that is associated with daily fatigue.  She has taken over-the-counter nonsteroidal anti-inflammatory agents, but they only temporarily relieve the pain.  The patient has no other medical issues.  She does not use tobacco, alcohol, or illicit drugs and is not sexually active.  Vital signs are within normal limits.  BMI is 35 kg/m².  The patient walks with a limp due to pain in the foot.  There is symmetric swelling, tenderness, and restricted range of motion involving the wrists, ankles, forefeet, and knees.  There is no skin rash.  Laboratory studies show anemia.  Which of the following is most likely to be the earliest finding during the development of this patient’s condition?