External cervical resorption (ECR) is an aggressive disease characterized by resorption of the tooth root structure. While the pericanalar resorption-resistant sheet (PRRS) impedes ECR progression towards the pulp, the underlying mechanisms of its protective role in human teeth remain unclear. This study aimed to elucidate the pathology of ECR in a 31-year-old female patient by employing radiographic, histological, and immunohistochemical analyses of an extracted tooth. Histological examination revealed that the PRRS comprised dentin, predentin, and reparative bone-like tissue. Notably, clastic cells were observed on the surfaces of all three tissues within the same specimens. Immunohistochemical staining for cathepsin K demonstrated diminished resorptive activity of clastic cells on predentin compared to dentin and bone-like tissue. These findings suggest a potential role for predentin in attenuating clastic cell activity, potentially serving as the final barrier safeguarding the pulp tissue.

Clear cell tumors of the lung (CCTL), or \"sugar tumors\" of lung, are very uncommon lesions and are mostly benign perivascular epithelioid cell (PEC) tumors with no specific morphologic features. Fewer than 100 cases have been reported; the aggressive nature demonstrated in sporadic reports has rarely been described in the literature. Although the course is generally described as benign, eight reported cases showed malignant behavior. We report a case of a PEC with a malignant presentation in a young man, correlating the main characteristics of the tumor with other cases reported in the literature to better elucidate this rare presentation. We also performed a literature review of reports on benign and malignant CCTL cases, with a focus on clinical, imaging, and immunohistochemical differentiation. CCTLs are rare tumors that require histopathological and immunohistochemical confirmation; to date, criteria that can predict malignant evolution are lacking.

A sufficiently stable noncovalent association complex between a covalent inhibitor and its protein target is regarded as a prerequisite for the formation of a covalent complex. As this transient form can hardly be assessed experimentally, computational modeling is required to probe the suitability of a given ligand at this particular stage. To investigate which criteria should be fulfilled by suitable candidates in a molecular dynamics (MD) assessment, a systematic study was conducted with 20 complexes of cathepsin K, a papain-like cysteine protease of pharmaceutical relevance. The covalent inhibitors in these complexes were converted to their pre-reaction states, and the resulting noncovalent complexes were subjected to MD simulations. The critical distance between the electrophilic and nucleophilic reaction partners was monitored as a potential parameter to assess the suitability for covalent bond formation. Across various warhead types, a distance between 3.6 and 4.0 Å, comparable to the sum of the generalized Born radii of carbon and sulfur, was found to be stably maintained under appropriate conditions. The protonation state of the catalytic dyad and the resulting solvation pattern dramatically affected the noncovalent binding mode and the distance of the warhead to the active site. For several complexes, fluctuations in the orientation of the warhead were observed due to torsional rotations in adjacent bonds. This observation helped to explain the gradual transitions from noncovalent to covalent complexes observed in the crystal structures of three closely related nitrile-based inhibitors. According to comparative simulations conducted for a set of 13 cathepsin S complexes, the overall findings of the study appear to be transferable to related cysteine proteases as targets of covalent inhibitors.

We describe a case in which a 41-year-old pregnant female with pycnodysostosis presented for elective cesarean section at week 37 + 5 of pregnancy. This is the first reported case of pycnodysostosis during pregnancy in Oman, to the author\'s best knowledge.

BACKGROUND: Pycnodysostosis is a rare disease secondary to a mutation in gen 1q21 that codifies the cathepsin K, proteolitic enzyme implicated in the metabolism of osteonectin, osteopontin and type I colagen. Its global incidence is around 1-1.7 cases per million, without genre prevalences, it is clinically caracterized by short stature, craneal deformities, «birds face» and bone fragility with pathological fractures tendency predominantly affecting long bones and occasionally vertebral pedicles. Radiologically is characterized by sclerous bones with permeable medular cannel. Despite there are numerous clinical reports on medical literature, just a litlle describe families with more than one afected member and its followship is usually short-term.
OBJECTIVE: To analize clinical evolution of these afected patients.
METHODS: A retrospective, descriptive, observational study was reelized in three patients with diagnosis of pycnodisostosis, between July 2006 and March 2016.
RESULTS: different affection forms of pycnodisostosis where observed, some of them, atipical, as for example spondilolisis and a escapule fracture in one patien.
CONCLUSIONS: The present study could be the longest longitudinal report ever registered. By knowing the presented variety of manifestations and complications, the reader could select the best treatment method for each case.
UNASSIGNED: La picnodisostosis es una rara enfermedad secundaria en una mutación en el gen 1q21 que codifica la catepsina K, enzima implicada en el metabolismo de osteonectina, osteopontina y colágeno I. La incidencia mundial es de 1-1.7 casos por millón, sin prevalencia por género, se caracteriza clínicamente por talla baja, deformidades craneales, «cara de pájaro» y fragilidad ósea con tendencia a fracturas patológicas, que afectan predominantemente los huesos largos y ocasionalmente en los pedículos vertebrales. Radiológicamente es característica la presencia de osteoesclerosis con canales medulares permeables. Aunque existen numerosos reportes de casos clínicos en la literatura, pocos son los que describen familias con más de un individuo afectado y el seguimiento suele ser a corto plazo.
OBJECTIVE: Analizar la evolución clínica de los pacientes afectados.
UNASSIGNED: Se realizó estudio retrospectivo, descriptivo, observacional de tres pacientes con diagnóstico de picnodisostosis, en el período de Julio 2006 a Marzo de 2016.
RESULTS: Se observaron diferentes formas de afectación de la picnodisostosis, algunas de ellas atípicas como la espondilólisis y una fractura de escápula en una paciente.
CONCLUSIONS: El presente estudio podría ser el análisis longitudinal más extenso del que se tenga registro. Conocer la variedad de manifestaciones y complicaciones presentadas permitirá al lector seleccionar el mejor método de tratamiento para cada caso.

We report a 48-year-old Japanese man with a brown tumor of the right distal tibia. At the age of 25 years, hemodialysis was initiated due to nail-patella syndrome. Severe secondary hyperparathyroidism and osteoporosis progressed over time, so parathyroidectomy was performed at age 45. Spontaneous fracture of the right distal tibia occurred suddenly at age 48. Imaging studies revealed a bone tumor-like lesion and surgery was performed. The resected specimen was a brown mass consisting of multinucleated giant cells on a fibrous tissue background, and these findings were consistent with a diagnosis of brown tumor. Immunohistochemistry revealed that multinucleated giant cells near areas of bone matrix were positive for tartrate-resistant acid phosphatase and cathepsin K, but the majority of the giant cells in the lesion were negative for these markers. Even after parathyroidectomy, brown tumor should be considered in the differential diagnosis of bone tumor-like lesions in patients on long-term dialysis. This case suggests that osteoclast activation may not contribute to development of brown tumors, although these lesions are generally considered to arise from subperiosteal bone resorption related to osteoclast overactivity in patients with hyperparathyroidism.

BACKGROUND: Pycnodysostosis is a rare autosomal recessive skeletal dysplasia caused by a mutation in the cathepsin K encoded by cathepsin K gene (CTSK). Medullary thyroid carcinoma (MTC) is also a relatively rare type of primary thyroid carcinoma.
METHODS: A 31-year-old woman presenting a short stature and a palpable nodule in the front of her neck that had gradually increased in size during the last 2 years was referred to our department. She has experienced multiple fractures at lower limbs in the last 2 decades.
METHODS: The patient\'s clinical examination revealed short stature, underweight, a prominent forehead, stubby fingers, and a fixed nodule in the right thyroid lobe. Intraoral examination revealed multiple clinically malposed and missing teeth, as well as chronic periodontitis with a narrow and grooved palate. Radiographic examination revealed typical widely separated cranial sutures and an open anterior/posterior fontanel with an obtuse gonial angle, acroosteolysis, and osteosclerosis with narrowed medullary cavities. Ultrasonography of the thyroid gland showed a marked hypoechoic solid nodule in the right lobe in which tumor cell clusters were confirmed by ultrasound-guided fine needle aspiration biopsy and was suspected to be MTC. Laboratory tests revealed dramatically elevated serum calcitonin >2000 pg/L (reference range: 0-5 pg/L) and carcinoembryonic antigen (CEA) 134.37 ng/mL (reference range: 0-5 ng/mL). Genotypic screening revealed compound heterozygous mutations in the CTSK gene (c.158delA, P.Asn53Thr/c.C830T, P.Ala277Val) but no mutation associated with the familial forms of MTC.
METHODS: The patient underwent a total thyroidectomy with right-sided functional neck dissection.
RESULTS: CEA and serum calcitonin decreased significantly postthyroidectomy, and no further fracture has been reported by the patient so far.
CONCLUSIONS: The present study is the first to report a rare case of the coexistence of pycnodysostosis with a compound CTSK gene mutation and sporadic MTC. Radiological techniques and gene analysis play key roles in the definitive diagnosis.

BACKGROUND: Pycnodysostosis is a rare autosomal recessive skeletal dysplasia characterized by short stature, craniofacial dysmorphism, acro-osteolysis, osteosclerosis, and brittle bone with poor healing. Pycnodysostosis results from the deficient activity of cathepsin K, a lysosomal cysteine protease that is encoded by CTSK.
METHODS: We report a Korean adult patient with pycnodysostosis and atypical femur fracture whose diagnosis was confirmed by next-generation sequencing (NGS) of candidate genes. A 41-year-old female patient was presented with a left femur fracture after falling down. Underlying sclerotic bone disease was suspected as a radiographic skeletal survey showed thickened cortical bones, and the total body bone density was increased (T score was 5.3, and Z score was 4.9).
METHODS: We performed candidate gene sequencing of various sclerotic bone diseases for the differential molecular diagnosis of underlying sclerosing bone disease. Two heterozygous variants of CTSK were detected. One was a frameshift variant in exon 5, c.426delT (p.Phe142Leufs*19), which was previously reported, and the other was a novel missense variant in exon 6, c.755G>A (p.Ser252Asn). Sanger sequencing of CTSK confirmed the 2 heterozygous variants and thus the patient was diagnosed with pycnodysostosis.
METHODS: The patient had emergency surgery for subtrochantic femoral fracture.
RESULTS: After 4 months of surgery, the patient had almost a full range of hip and knee movements and radiographs show the substantial bridging callus across the fracture.
CONCLUSIONS: Candidate gene sequencing could be a useful diagnostic tool for the genetically heterogeneous skeletal dysplasia group, especially in cases with a mild or atypical clinical phenotype.

Fractures are an important entity to consider in pediatric patients. There are certain diseases in which bones fracture with a minimal trauma. Pycnodysostosis is an autosomal recessive unusual type of cráneo metaphyseal dysplasia, that presents frequently as fracture in a pathological bone. A 9 year old caucasian female, diagnosed with pycnodysostosis, was admitted with a right femur fracture as a result of a low energy trauma. Radiographic studies showed bilateral femur fractures, proximal fracture and non-union in antecurvatum of the left tibia. Pycnodysostosis is a rare disease, generally diagnosed at an early age by growth restriction, frequent fractures or fractures with low energy trauma. Therapy alternatives are limited, and no permanent cure has been developed. If a patient has dysmorphic facial features and fractures in a pathological bone, it is important to suspect bone dysplasia, such as pycnodysostosis and its differential diagnoses.
Las fracturas en edad pediátrica son una entidad importante para considerar. Hay enfermedades en que los huesos del niño se fracturan ante traumatismos de menor energía. La picnodisostosis es un tipo inusual de displasia cráneo-metafisaria autosómica recesiva, cuya primera manifestación clínica suele ser una fractura en hueso patológico. Se presenta a una paciente, caucásica, de 9 años de edad, con diagnóstico de picnodisostosis, que ingresó al hospital por fractura del fémur derecho, por un mecanismo de baja energía. Los estudios radiográficos mostraron fracturas del fémur bilateral, fractura proximal de la tibia izquierda y consolidación viciosa en antecurvatum. Esta rara enfermedad se diagnostica a edades tempranas por talla baja, por fracturas repetidas o por traumas de baja energía. Las opciones terapéuticas son limitadas, y no se ha desarrollado una cura definitiva. Es importante, ante un paciente pediátrico con rasgos dismórficos faciales y fracturas en hueso patológico, sospechar displasias óseas, tales como la picnodisostosis y sus diagnósticos diferenciales.

暂无摘要。