MRCP2-2507
A 65-year-old female presents with a 6-month history of increasing lethargy and malaise. She has no past medical history and travels widely, last visiting the Middle East two weeks prior to this admission, returning with a respiratory tract infection that appears to be resolving. She is a lifelong non-smoker and does not drink alcohol to excess. Over the past four weeks, she reports increasing bilateral persistent headache associated with binocular visual blurring. In addition, she describes a non-specific abdominal discomfort without any changes in bowel habit.
On examination, you note bilateral axillary lymphadenopathy and conjunctival pallor. Cardiovascular and respiratory system examinations were unremarkable. Neurological examination is unremarkable. Fundoscopy reveals dilated tortuous retinal veins. Abdominal examination reveals hepatosplenomegaly. Lastly, you note areas of purpura around her left anterior shin and her right upper arm. A chest radiograph is unremarkable.
Her blood results are as follows:
Hb 87 g/l
MCV 79 fl
Platelets 190 * 109/l
WBC 3.4 * 109/l
Na+ 142 mmol/l
K+ 4.5 mmol/l
Urea 7.6 mmol/l
Creatinine 89 µmol/l
Adj Calcium 2.47 mmol/l
Phosphate 1.34 mmol/l
LDH 1890 (normal range 140-280 units/L)
Serum electrophoresis IgM paraprotein band at 5.4 g/L
A bone marrow biopsy demonstrates 14% infiltration of lymphoplasmacytic cells
What is the most likely diagnosis?