Pulmonary Cavitation With Eosinophilia in a Young Man.

CASE PRESENTATION: An 18-year-old man with no noted medical history from Northern India presented with history of fever for 15 days and nocturnal cough for 10 days. He denied breathlessness or wheeze. There was no medical history of asthma. He denied any current sinus-related symptoms, pruritis, skin rashes, lesions, or ulcers, abdominal pain, dysphagia, vomiting or diarrhea, numbness or tingling, joint pain, or food allergy. There was no recent exposure to a patient with TB or history of substance misuse. The patient had sought medical care 7 days before presentation for the same symptoms, and after a chest radiograph was obtained, the patient was started on an antitubercular regimen.

Methotrexate induced pneumonitis - A case report and review of literature.

Methotrexate (MTX) is the commonly preferred drug in the treatment of various chronic inflammatory conditions. An uncommon, life-threatening, and fatal event associated with methotrexate use is methotrexate-induced pneumonitis (M-pneu). M-pneu does not correlate with the dosage, duration, or method of administration. We present a case of M-pneu in a diagnosed rheumatoid arthritis patient after six years of initiation of MTX. Prompt recognition, withdrawal, and supportive therapy have a positive outcome. If untreated, M-pneu has a proven fatality of 17-30% in published cases.

Thoracic follicular dendritic cell sarcoma - an outlandish presentation of a rare tumour with review of literature.

Follicular dendritic cell sarcoma is a rare low grade malignant neoplasm that arises from follicular dendritic cells in lymphoid tissue germinal centres and accounts for 0.4% of all soft tissue sarcomas. It is extremely rare to have pulmonary follicular dendritic cell sarcoma with endobronchial extension and as an anterior mediastinal mass with mediastinal lymph node involvement. We present the case of a 34-year-old male non-smoker who had been experiencing chest pain for three months. A lobulated left peri-hilar mass with endobronchial spread into the left main bronchus and mediastinal lymphadenopathy was identified on a chest CT. The bronchoscope-guided cryobiopsy of the endobronchial mass was inconclusive. After a thorough multidisciplinary discussion, the patient underwent left sided pneumonectomy, mediastinal mass resection, and systematic lymph node dissection. Histologic examination using immunohistochemistry revealed follicular dendritic cell sarcoma.

The master impersonator: Pulmonary tuberculosis mimicking diffuse cystic lung disease - A mini case series of a rare presentation.

Pulmonary tuberculosis has diverse clinical presentations. Cysts in the lung can arise due to large number of causes out of which tuberculosis is very rare. We report two immunocompetent cases of pulmonary tuberculosis who presented with multiple cysts in the lung parenchyma. The diagnosis was confirmed by the transbronchial lung cryobiopsy in first case and by analysis of bronchoalveolar lavage fluid in the second. Both had spontaneous pneumothorax which was treated with chest drain and pleurodesis. Both showed an excellent response to anti-tubercular therapy and steroids. Tuberculosis presenting as cystic lung disease is atypical and rare.

Optimal Protein Sequence Design Mitigates Mechanical Failure in Silk ß-Sheet Nanocrystals.

The excellent mechanical strength and toughness of spider silk are well characterized experimentally and understood atomistically using computational simulations. However, little attention has been focused on understanding whether the amino acid sequence of ß-sheet nanocrystals, which is the key to rendering strength to silk fiber, is optimally chosen to mitigate molecular-scale failure mechanisms. To investigate this, we modeled ß-sheet nanocrystals of various representative small/polar/hydrophobic amino acid repeats for determining the sequence motif having superior nanomechanical tensile strength and toughness. The constant velocity pulling of the central ß-strand in the nanocrystal, using steered molecular dynamics, showed that homopolymers of small amino acid (alanine/alanine-glycine) sequence motifs, occurring in natural silk fibroin, have better nanomechanical properties than other modeled structures. Further, we analyzed the hydrogen bond (HB) and ß-strand pull dynamics of modeled nanocrystals to understand the variation in their rupture mechanisms and explore sequence-dependent mitigating factors contributing to their superior mechanical properties. Surprisingly, the enhanced side-chain interactions in homopoly-polar/hydrophobic amino acid models are unable to augment backbone HB cooperativity to increase mechanical strength. Our analyses suggest that nanocrystals of pristine silk sequences most likely achieve superior mechanical strength by optimizing side-chain interaction, packing, and main-chain HB interactions. Thus, this study suggests that the nanocrystal ß-sheet sequence plays a crucial role in determining the nanomechanical properties of silk, and the evolutionary process has optimized it in natural silk. This study provides insight into the molecular design principle of silk with implications in the genetically modified artificial synthesis of silk-like biomaterials.

Tyrosine in the hinge region of the pore-forming motif regulates oligomeric ß-barrel pore formation by Vibrio cholerae cytolysin.

ß-barrel pore-forming toxins perforate cell membranes by forming oligomeric ß-barrel pores. The most crucial step is the membrane-insertion of the pore-forming motifs that create the transmembrane ß-barrel scaffold. Molecular mechanism that regulates structural reorganization of these pore-forming motifs during ß-barrel pore-formation still remains elusive. Using Vibrio cholerae cytolysin as an archetypical example of the ß-barrel pore-forming toxin, we show that a key tyrosine residue (Y321) in the hinge region of the pore-forming motif plays crucial role in this process. Mutation of Y321 abrogates oligomerization of the membrane-bound toxin protomers, and blocks subsequent steps of pore-formation. Our study suggests that the presence of Y321 in the hinge region of the pore-forming motif is crucial for the toxin molecule to sense membrane-binding, and to trigger essential structural rearrangements required for the subsequent oligomerization and pore-formation process. Such a regulatory mechanism of pore-formation by V. cholerae cytolysin has not been documented earlier in the structurally related ß-barrel pore-forming toxins.