Osteopetrosis, autosomal dominant


Step 1: View clinicals

A 22-year-old woman is referred for further evaluation of a fractured left femur, sustained after she slipped and fell on a flat floor yesterday. X-rays showed a transverse subtrochanteric fracture, with markedly dense cortical boundaries and a reduced intramedullary diameter. Her medical and surgical histories are unremarkable, and she is not on any medications. Her mother experienced a foot fracture and a Colles fracture at the ages of 32 and 55 years respectively. These were treated individually, without further evaluation. She is a student at the local community college, has never smoked, and only drinks socially. A complete blood count is significant for a Hb of 10.5 g/dL (normal: 12-18), with normal MCV, MCH and MCHC values. Peripheral smears confirm normochromic normocytic anemia. A reticulocyte count is 0.5% (normal: 0.5-1.5). Her ESR, CRP, and renal and liver profiles (including serum alkaline phosphatase levels) are all within normal parameters.

Step 2: Order all relevant investigations

Serum TSH and PTH

Serum thyroid stimulating hormone (TSH) and parathyroid hormone (PTH) levels are within normal parameters.

Skeletal survey

Skull: thickening of the inner and outer cortical tables, with increased radiodensity at the skull base. Spine: increased radiodensity of all vertebrae, with sclerotic bands over the endplates (i.e. "sandwiched vertebrae" appearance). Pelvis: expanding osteosclerosis of the pelvic bones, with a "bone within a bone" appearance.

Serum tartrate-resistant acid phosphate

Serum tartrate-resistant acid phosphate (TRAP): 50 U/L (3.5–9.1)

Transiliac bone biopsy

You realize that transiliac bone biopsy is not indicated here.

Step 3: Select appropriate management

High dose vitamin D
Gamma-1b interferon

Score: ★★☆