Endocrine Abstracts

Background: Osteopetrosis is a rare chronic bone disease with high bone mineral densitiy due to impaired osteoclast activity or development. Genetic mutations result in severe infantile (autosomal recessive, incidence 1:200,000) and less severe adult forms (autosomal-dominant osteopetrosis/ADO). The incidence is estimated at 1:20,000 for noninfantile forms. In adults osteopetrosis is often asymptomatic with increased risk for bone fracture. Treatment is symptom-based (e.g. calcium, cholecalciferol, calcitriol, red blood cell transfusion, interferon γ-1b, corticosteroids) since effective therapy is missing.

Case report: Twenty-seven year old male patient with a history of osteopetrosis for 9 years (self-employed photographer, working abroad, surfer/skater, smoker). Osteopetrosis was radiographically diagnosed in context with car accident and traumatic fracture of left clavicle. Further typical findings in spine (‘sandwich vertebrae’), ribs, upper and lower limbs were detected in computertomography because of unclear abdominal pain and transient increased cervical lymph nodes 08/2017. Consultation of endocrinologist in 10/2017: No further bone fractures since 2008, slight pain of caudal left ribs after bruising, no routine medication. Diagnostic expert-based recommendations were taken from recent consensus guidelines from the osteopetrosis working group (Wu et al. 2017).

Results: Increased: tartrate-resistant acid phosphatase/TRAP5b: 54 U/l (1.4–6.1), BB isozyme of creatine kinase (CK-BB): 0.77 μkat/l (0.0 in healthy persons); bone mineral density (in g/cm²: L1–L4 2.981; right femur 2.509; left femur 2.585) and T-score in DXA-scan (L1–L4+14.7; right femur +10.9; left femur +11.5 S.D.). Genetic analysis confirmed CLCN7 mutation (heterozygous) and thus autosomal dominant osteopetrosis type 2 (ADOII, Albers-Schönberg disease). MRI was cancelled due to metal near right orbita. Native computertomography of the brain excluded cranial (optic) nerve impingement but confirmed generalized thickening of the bone. Subspecial clinical complications (ophthalmology, hematology), pathologic alterations in renal ultrasonography and abnormal blood count (with differential), lactate dehydrogenase, serum calcium, intact parathyroid hormone, phosphorus, creatinine, 25-hydroxyvitamin D were not seen. Clinical controls and minimum laboratory (serum calcium, phosphorus, 25(OH)D, parathyroid hormone, blood count) were arranged half-yearly as recommended above (Wu et al. 2017). We clarified the patient of an increased risk of spontaneous and traumatic bone fracture with risky sports.

Conclusions: We established the patient’s diagnosis ADO biochemically and genetically after first radiographic signs were confirmed one decade ago. Patients with osteopetrosis need to be monitored lifelong if appropriate in a multidisciplinary setting. Since epidemiological and clinical data is lacking publication of case reports is crucial.