Von Recklinghausen's disease of bone with multiple osteolyses and bone fractures due to malnutrition in an 83 years old patient

An 83-year-old woman presented to our surgical department with pain and oedema in the lower left leg, fatigue and weight loss of 35 kg in the previous year. Clinical examination revealed cachexia, kyphosis and scoliosis. X-ray showed a left tibial fracture. Initial laboratory examinations were normal with the exception of mild hypocalcaemia (2,04 mmol/l). A CT scan and bone scintigraphy detected numerous unstable osteolyses, indicative of bone metastases or multiple myeloma. Immunofixation, thoracic/abdominal CTs and mammography did not detect the presence of any malignant disease, therefore biopsy of the osteolytic lesions was performed. Histologically, both tumor and haematological disease were excluded. Proliferating fibrous tissue with haemosiderin deposition was detected, a finding typical for advanced hyperparathyroidism. Subsequent laboratory testing confirmed high parathyroid hormone (831 pg/ml) with undetectable 25-OH-Vitamin D concentrations. Additionally, bone densitometry demonstrated advanced demineralization (T-score spine -4,2/hip -4,3). The relatives reported that the patient had dramatically reduced her daily calorie intake in the last year due to major depression. Oral calcium- and i.m vitamin D-substitution, high calorie nutrition and therapy with denosumab were established. In conclusion, vitamin D deficiency due to malnutrition in this patient led not only to osteomalacia (vitamin D dependent rickets), but also to extreme secondary hyperparathyroidism with consecutive development of 'brown tumors', a condition known as von Recklinghausen's disease of bone or osteitis fibrosa cystica. This disease is mainly observed in patients with either untreated primary or advanced secondary hyperparathyroidism due to chronic kidney disease. However this case indicates that malnutrition for a relatively short period can also lead to von Recklinghausen's disease of bone with a complicated clinical course that can be misinterpreted as malignant bone disease.