Pycnodysostosis is an autosomal recessive disorder characterized by osteosclerosis, small stature, acro-osteolysis of the distal phalanges, loss of the mandibular angle, separated cranial sutures with open fontanels, and frequent fractures. One identified cause of the disease is reduced activity of the cysteine protease cathepsin K. A 48-year-old woman with a history of frequent fractures presented with a severe gait disturbance. Radiography, computed tomography, magnetic resonance imaging, and gene analysis were performed. Physical examination revealed open fontanels, and radiographs showed increased bone density. DNA sequence analysis revealed a deletion mutation of the cathepsin K gene. We diagnosed pycnodysostosis based on these findings. The magnetic resonance and computed tomography images demonstrated multilevel spinal canal stenosis due to ossification of the yellow ligament. We performed a laminectomy, and the patient's neurological signs and symptoms improved. To our knowledge, this is the first case of pycnodysostosis with ossification of the yellow ligament.
Acro-Osteolysis ; Bone Density ; Cathepsin K ; Constriction, Pathologic* ; Cranial Sutures ; Cysteine Proteases ; Female ; Gait ; Humans ; Laminectomy ; Ligaments* ; Magnetic Resonance Imaging ; Middle Aged ; Osteosclerosis ; Physical Examination ; Pycnodysostosis* ; Radiography ; Sequence Analysis, DNA ; Sequence Deletion ; Spinal Canal*

The diagnosis of pituitary carcinoma cannot be made easily histologically, and most cases of pituitary carcinoma are diagnosed only after the clinical detection of metastasis. Distant metastasis of pituitary tumor occurs in 0.1% to 0.2% of cases and has been reported in the liver, bone and central nervous system, with only one case of metastasis to the cauda equine reported. This study describes a rare case of the drop metastasis of adrenocorticotropic hormone-producing pituitary adenocarcinoma to the cauda equina, causing cauda equina syndrome.
Adenocarcinoma ; Adrenocorticotropic Hormone ; Cauda Equina* ; Central Nervous System ; Diagnosis ; Liver ; Neoplasm Metastasis* ; Pituitary Neoplasms* ; Polyradiculopathy