Patient

The research protocol was approved by the ethics committee of West China Hospital of Sichuan University. All participants provided written informed consent before participating in the study.

A 43-year-old man was first seen at the outpatient unit of West China Hospital, with complaints of discomfort in his lower extremities for 5–6 years. The radiographs revealed “bone-in-bone” in the pelvis wing, a “sandwich” spine, and sclerosis of the base of the skull, which are characteristic of ADO2 (Figure 1). The patient’s serum TRAP-5b was significantly elevated (>10 U·L⁻¹), and his parathyroid hormone (PTH) level was at the upper limit of the normal range (6.18 pmol·L⁻¹).The patient’s type I collagen C-telopeptide (CTX) level (0.364 ng·mL⁻¹) was at the lower limit of the normal range. The patient’s serum levels of bone-specific alkaline phosphatase (B-ALP), 25-OH-VD, calcium, phosphate, and magnesium were within the normal range (Table 1). The patient’s mean bone mineral density, T and Z scores of lumbar vertebrae, L1–L4, were 1.65, 4.7, and 4.5 g·cm⁻², respectively. His mean bone mineral density, T and Z scores for the femoral neck were 1.292, 2.4, and 2.5 g·cm⁻², respectively. The patient had no history of fracture. According to the clinical features and imaging data of the patient, he was clinically diagnosed as ADO2, and other types of osteopetrosis and skeletal fluorosis were excluded. No similar symptoms were found in his first-degree relatives.

Radiographic examination reveals diffuse osteosclerosis in an ADO2 patient. (a) Bone-in-bone in the pelvis wing (arrow). High-bone density under the cartilage in the pubic symphysis (arrow). (b) ADO2-characteristic sandwich shape of the vertebral body. (c) Osteosclerosis in the base of the skull (arrow). (d) Osteosclerosis in the distal metaphysis of the femur (arrow).

Abbrevations: RBC, red blood cells; Hgb, hemoglobin; WBC, white blood cells; TRAP-5b, tartrate-resistant acid phosphatase type 5b; CTX, type I collagen C-telopeptide; B-ALP, bone-specific alkaline phosphatase; PTH, parathyroid hormone.