A 31-year-old woman, gravida 2, para 0-1-0-0, at 11 weeks gestation comes to the clinic fo… — USMLE Step 2 CK

A $31$ -year-old woman, gravida $2$ , para $0-1-0-0$ , at $11$ weeks gestation comes to the clinic for an initial prenatal visit. Her first pregnancy ended in a fetal demise at $22$ weeks gestation. She has a history of a left lower extremity deep venous thrombosis $3$ years ago following a transatlantic flight, for which she completed a $6$ -month course of warfarin. Today, she feels well. Blood pressure is $110/70$ mm Hg, and pulse is $84$ /min. Physical examination is unremarkable. Laboratory results are as follows:

Laboratory Test	Result	Reference Range
Hemoglobin	$11.2$ g/dL	$12.0-16.0$ g/dL (non-pregnant)
Platelet count	$125,000$ /mm $^3$	$150,000-400,000$ /mm $^3$
Serum bicarbonate	$20$ mEq/L	$22-28$ mEq/L
Arterial PCO $_2$	$30$ mm Hg	$35-45$ mm Hg
TSH	$0.2$ $\mu$ U/mL	$0.1-2.5$ $\mu$ U/mL (1st trimester)
Free T4	$1.3$ ng/dL	$0.8-2.0$ ng/dL
aPTT	$52$ seconds	$25-35$ seconds

Additional testing shows a positive rapid plasma reagin (RPR) but a negative fluorescent treponemal antibody absorption (FTA-ABS) test. Urinalysis shows trace protein. Which of the following is the most appropriate next step in management?

Subcutaneous low-molecular-weight heparin and oral low-dose aspirinCevap
B
Intravenous ceftriaxone and oral azithromycin
C
Observation and routine prenatal care
D
Initiation of oral propylthiouracil
E
Administration of intravenous sodium bicarbonate

Cevap

Subcutaneous low-molecular-weight heparin and oral low-dose aspirin

This patient's clinical history (second-trimester fetal demise and unprovoked deep venous thrombosis) combined with her laboratory findings (prolonged aPTT and biologic false-positive RPR) is highly characteristic of Antiphospholipid Syndrome (APS). The false-positive RPR is caused by anticardiolipin antibodies, while the prolonged aPTT is an in vitro artifact caused by the lupus anticoagulant. Despite the in vitro prolongation, APS causes a severe hypercoagulable state in vivo. For pregnant patients with APS who have a history of prior thromboembolism, the standard of care is therapeutic-dose low-molecular-weight heparin (LMWH) and low-dose aspirin to prevent recurrent venous thromboembolism and severe obstetric complications (e.g., recurrent fetal demise, severe preeclampsia).

Adım Adım Çözüm

Analyze the hematologic and infectious disease laboratory findings.

The patient has a prolonged aPTT and a false-positive RPR (positive RPR with negative FTA-ABS).

These findings are classic laboratory artifacts caused by circulating lupus anticoagulant (prolongs aPTT in vitro) and anticardiolipin antibodies (cross-reacts with RPR antigen).

Synthesize the laboratory findings with the patient's obstetric and medical history.

The combination of a prior DVT, a second-trimester fetal demise, and antiphospholipid antibodies confirms the diagnosis of Antiphospholipid Syndrome (APS).

APS diagnosis requires at least one clinical criterion (vascular thrombosis or specific pregnancy morbidity) and one laboratory criterion (lupus anticoagulant, anticardiolipin, or anti-beta-2-glycoprotein I antibodies).

Differentiate pathologic findings from the normal physiologic changes of pregnancy.

The mild anemia, low PCO2, low bicarbonate, and low TSH are all normal physiologic adaptations to pregnancy and do not require targeted therapy.

Progesterone causes central hyperventilation (respiratory alkalosis), hCG mildly suppresses TSH, and plasma volume expansion causes dilutional anemia.

Determine the appropriate management for a pregnant patient with APS and a history of thrombosis.

The patient requires therapeutic-dose low-molecular-weight heparin (LMWH) and low-dose aspirin.

Despite the prolonged aPTT in vitro, APS is a highly thrombophilic state in vivo. Anticoagulation is required to prevent recurrent maternal DVT and placental thrombosis leading to fetal demise.

Anahtar Kavram

Antiphospholipid Syndrome (APS) in pregnancy presents with a history of recurrent miscarriages or thrombosis, prolonged aPTT, and false-positive syphilis testing; it requires treatment with LMWH and low-dose aspirin.

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Cevap

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