Osteopetrosis

A 3-year-old girl is brought to the pediatrician for evaluation of decreased hearing in the left ear. The symptoms started 2 months ago and have progressively worsened. Her parents state she has difficulty hearing voices and sounds coming from her left. Past medical history is notable for a femoral fracture, which she sustained after falling from standing-height. There is no history of similar symptoms in her family members. The patient’s older sister was recently diagnosed with multiple sclerosis at the age of 20. Temperature is 37.3°C (99.1°F), blood pressure is 110/65 mmHg, and pulse is 87/min. The patient is below the 5th percentile for height and weight. Physical examination is notable for hepatosplenomegaly and sensorineural hearing loss in the left ear. Genetic testing reveals a homozygous mutation in the carbonic anhydrase type II gene (CA2). Which of the additional findings will most likely be present on laboratory testing?