Experience the Quality With Free USMLE Exam Questions That Helps Candidates Pass

Vasa previa occurs when fetal vessels run across or near the cervical os, unprotected by the placenta or umbilical cord. Rupture leads to painless vaginal bleeding, fetal bradycardia, and rapid fetal exsanguination. Placenta previa also causes painless bleeding but involves placental implantation over the cervical os, not fetal vessels. Placental abruption causes painful bleeding with uterine tenderness. Uterine rupture occurs with prior uterine surgery and presents with abdominal pain and loss of fetal station. Diagnosis of vasa previa can be made prenatally by ultrasound with Doppler. Management includes planned cesarean delivery before labor onset to prevent fetal demise.

Mobitz type II second-degree AV block is characterized by constant PR intervals with intermittent non-conducted P waves (dropped QRS complexes). Unlike Mobitz type I (Wenckebach), which shows progressive PR prolongation, Mobitz type II is more serious and often progresses to complete heart block. First-degree AV block shows prolonged PR (>200 ms) with all beats conducted. Complete AV block (third-degree) shows dissociation of atrial and ventricular activity. Mobitz II is due to disease of the His-Purkinje system and often requires pacemaker placement due to risk of sudden cardiac arrest. Recognition of constant PR intervals with sudden dropped beats is key for diagnosis.

Bullous pemphigoid is an autoimmune blistering disorder caused by IgG antibodies against hemidesmosomes (BP180, BP230) at the dermoepidermal junction. It presents in elderly patients with tense, pruritic bullae on the trunk and extremities. Mucosal involvement is rare. Histology shows subepidermal blisters with linear IgG and C3 deposition along the basement membrane on immunofluorescence. Pemphigus vulgaris is caused by antibodies against desmoglein 1/3, presenting with flaccid bullae, mucosal involvement, and a positive Nikolsky sign. Dermatitis herpetiformis is associated with celiac disease and shows granular IgA at dermal papillae. Erythema multiforme presents with targetoid lesions. Treatment of bullous pemphigoid includes corticosteroids and immunosuppressants. Prognosis is better than pemphigus vulgaris.

Goodpasture syndrome is an autoimmune disease characterized by circulating anti–glomerular basement membrane (anti-GBM) antibodies targeting the α3 chain of type IV collagen in both renal glomeruli and pulmonary alveoli. The result is rapidly progressive glomerulonephritis with hematuria and crescentic glomeruli on biopsy, combined with pulmonary hemorrhage causing hemoptysis. Young men are often affected. Granulomatosis with polyangiitis (Wegener) also causes hematuria and hemoptysis but is ANCA-associated (c-ANCA, PR3 antibodies) and features sinus disease and granulomas. Microscopic polyangiitis is p-ANCA (MPO) associated and lacks granulomas. Post-streptococcal GN presents after infection with low complement and immune complex deposits, not anti-GBM antibodies. Management of Goodpasture includes plasmapheresis to remove antibodies, high-dose corticosteroids, and immunosuppressants (cyclophosphamide). Early diagnosis is critical to preserve renal function and prevent fatal pulmonary hemorrhage.

Benign prostatic hyperplasia (BPH) arises from hyperplasia of prostatic stromal and epithelial cells, primarily in the transitional zone surrounding the urethra. Symptoms include urinary hesitancy, weak stream, incomplete emptying, nocturia, and frequency—collectively termed lower urinary tract symptoms. DRE typically shows a smooth, symmetrically enlarged prostate. PSA can be mildly elevated due to increased gland volume, though markedly elevated levels warrant evaluation for malignancy. Prostate cancer often originates in the peripheral zone, presenting as a firm, nodular, asymmetric prostate. Chronic prostatitis presents with dysuria, pelvic pain, tender boggy prostate, and recurrent UTIs. Bladder carcinoma usually presents with painless gross hematuria, not obstructive voiding symptoms. BPH management ranges from lifestyle modification and α-1 blockers (e.g., tamsulosin) to 5-α-reductase inhibitors and surgical resection in severe cases.