Case presentation

A 79-year-old Caucasian man with a past medical history of Parkinson’s disease and hypertension presented to the emergency department after suffering a fall, injuring his left leg. Vitals on initial presentation showed a heart rate of 112 beats per minute, blood pressure 130/88 mmHg, afebrile, respiratory rate 18 breaths per minute, and oxygen saturation 90% on room air. He denied any history of alcohol use, smoking, or illicit drug use. He did not have any significant family medical history and denied any past surgical history. His home medications included losartan 25 mg daily and carbidopa 25 mg-levodopa 100 mg daily. Table 1 highlights the patient's laboratory values at the time of admission. Computed tomography angiography (CTA) of the abdomen and pelvis was performed, which demonstrated a retroperitoneal hematoma of the left psoas and iliacus. He was transfused with one unit of packed red blood cells due to a low hemoglobin (Hgb) level of 6.6 g/dL, and the patient was admitted for further treatment and workup.

Parameter | Result | Reference Range
Hemoglobin (Hgb) | 6.6 g/dL | Male: 13.5-17.5 g/dL
Hematocrit (HCT) | 24.5% | Male: 40-54%
Prothrombin time (PT) | 15.8 seconds | 9.4-12.5 seconds
Activated partial thromboplastin time (aPTT) | 103.9 seconds | 25-37 seconds

Physical exam was most notable for a limited range of motion of the left leg with multiple blanching ecchymoses on all four extremities. Further hematologic workup results can be seen below in Table 2. An F VIII inhibitor profile was ordered, which showed an F VIII inhibitor titering assay (Bethesda) level of 1084 BU, and the patient was diagnosed with AHA. Further workup to identify the etiology of the acquired F VIII deficiency was initiated, including a CT chest scan, which found no occult masses. Antinuclear antibody and rheumatoid factor tests were performed to screen for autoimmunity, which were also unremarkable.

Parameter | Result | Reference Range
Factor XI activity level | <1% | 55-150%
Factor XII activity level | 28% | 55-180%
Fibrinogen | 586 mg/dL | 200-400 mg/dL
Partial thromboplastin time (PTT) 1:1 immediate mix | 90.2 seconds | 25.6-35.9 seconds
Prothrombin time (PT) 1:1 immediate mix | 15.0 seconds | 12.0-14.2 seconds
Lupus anticoagulant activated partial thromboplastin time (aPTT) | 139.7 seconds | 29.8-44.4 seconds
Lupus anticoagulant activated partial thromboplastin time (aPTT) mixing study | 118.2 seconds | 29.8-44.4 seconds
Hexagonal phase assay | Positive | N/A
Von Willebrand factor antigen | 465% | 55-200%
Factor VIII inhibitor titer | 1084 Bethesda Units (BU) | < 0.5 Bethesda Units (BU)

He was started on prednisone 1 mg/kg, and initially, his aPTT trended down until it plateaued 10 days into his steroid monotherapy. Figure 1 demonstrates his aPTT trend during his hospital course. Rituximab was initiated at 375 mg/m2 weekly for four weeks, and the prednisone dose was concomitantly lowered from 90 mg to 50 mg. Around 10 days later, on Day 41, the prednisone dose was increased to 100 mg due to an increase in aPTT. After receiving his third dose of rituximab, his aPTT reached 50.7 seconds, and the repeat Bethesda assay was 434 BU. While his iliopsoas hematoma size remained about the same throughout the hospitalization (8.3 x 6 cm), a repeat CTA scan during hospitalization showed markedly decreased attenuation, consistent with a resolving hematoma. He was safely discharged and continued prednisone treatment in the outpatient setting.

Figure 1: Graph of the patient’s aPTT trend throughout his hospital course.Day 25: prednisone 90 mg; Day 34: rituxan 375 mg/m2; Day 35: prednisone 50 mg; Day 43: prednisone 100 mg; Day 49: discharged