in septic arthritis, but neither is diagnostic. (e)A warm, swollen, painful
knee is concerning for osteomyelitis, which may cause decreased active
range of motion. However, passive range of motion should not be severely
compromised. A bone scan will detect osteomyelitis within 48 hours that
may not be immediately apparent on a plain radiograph.
172.The answer is a. (Harrison, pp 689-690.) This patient has
thrombotic thrombocytopenic purpura (TTP), caused by increased
platelet destruction. In TTP, platelet-fibrin thrombi deposit in vessel and
cause injury to RBCs and platelets, resulting in microangiopathy hemolytic
anemia and thrombocytopenia. Patients tend to be females who are 10 to
45 years of age. Risk factors include pregnancy, autoimmune disorders
(eg, systemiclupus erythematosus [SLE]), infection, allogenic bone marrow
transplantation, malignancy, and certain medications. The pentad can be
remembered with the mnemonic FAT RN: fever, hemolytic anemia, throm-
bocytopenia, renal failure, and neurologic change (waxing and waning men-
tal status). Treatment includes daily plasmapheresisuntil platelet count
normalizes. RBCs may be transfused in patients symptomatic from anemia
(eg, tachycardia, hypoxia, orthostatic hypotension). All patients with TTP
should be admitted to an ICU for close monitoring of acute bleeds.
(b)The therapy for TTP generally does notinclude platelet transfu-
sion, as this could worsen the condition and increase mortality. However,
platelets should be administered in patients who are having a life-threaten-
ing bleed (eg, an intracranial bleed). (c)Corticosteroids and splenectomy
are used in refractory cases, but plasmaphoresis is the mainstay of treat-
ment of TTP. (d)Hemolytic uremic syndrome (HUS) is a condition, most
common in children, thought to be on the same continuum as TTP. The
diagnostic triad includes renal failure, microangiopathic hemolytic anemia,
and thrombocytopenia. Fever and altered mental status are usually absent,
although seizures may result from complications of renal failure. HUS is
often associated with infection with E coliorShigella dysenteriaeor inges-
tion of undercooked meats or unpasteurized foods. (e)Fever and altered
mental status may indicate meningitis, but this patient has other signs and
symptoms consistent with TTP. A LP is unnecessary and could be danger-
ous given the very low platelet count.
173.The answer is a.(Tintinalli, pp 870-871, 913-918, 1517-1519.)This
patient suffers from toxic shock syndrome (TSS),a severe, life-threaten-
ing syndrome characterized by high fever, diffuse macular erythroderma,
194 Emergency Medicine