Introduction Chlamydia pneumoniae is an obligate intracellular Gram-negative bacterium that is a significant cause of respiratory tract infections worldwide. First isolated in 1983 by T. Brunham and colleagues, C. pneumoniae is a leading pathogen responsible for community-acquired pneumonia (CAP), bronchitis, and other respiratory illnesses. It is estimated to account for 10–20% of all CAP cases,…
Adult-onset Still’s disease (AOSD) is a rare, systemic inflammatory disorder characterized by a constellation of systemic and musculoskeletal manifestations. First described by George Still in 1897 as a childhood illness (Still’s disease), it was later recognized as a distinct entity in adults, now termed Adult-Onset Still’s Disease. AOSD affects approximately 1.4 to 12.3 cases per…
Overview and Epidemiology Familial Mediterranean Fever (FMF) is a rare, autosomal recessive autoinflammatory disorder characterized by recurrent episodes of fever and inflammation. It primarily affects individuals of Mediterranean and Middle Eastern descent, including those of Armenian, Turkish, Arab, Sephardic Jewish, and Greek origin. FMF is one of the most common hereditary autoinflammatory syndromes worldwide, with…
Sunflower syndrome is a rare and distinctive form of generalized epilepsy characterized by highly stereotyped seizure activity that is uniquely triggered by exposure to bright light and accompanied by a specific motor behavior—waving one hand in front of the eyes. This syndrome, first formally described in the the early 2000s, has since gained attention due…
Introduction Graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT) and certain solid organ transplants, characterized by an immunological attack of donor-derived immune cells against recipient tissues. It remains a major determinant of morbidity and mortality following transplantation, with significant implications for long-term survival and quality of life. While advances…
Overview and Pathophysiology Onychomycosis, or tinea unguium, is a chronic fungal infection of the nail unit characterized by significant morbidity, including pain, secondary bacterial infection, and psychosocial distress. While often considered cosmetic, it can serve as a reservoir for dermatophyte transmission (e.g., Tinea pedis) and may exacerbate underlying systemic conditions. The etiology is primarily dermatophytic,…
Clinical Overview Cornelia de Lange Syndrome (CdLS) is a complex multi-systemic neurodevelopmental disorder characterized by significant intellectual disability, distinctive facial dysmorphism, growth retardation, and limb anomalies. It is primarily caused by mutations in genes encoding components of the cohesin complex, which plays a critical role in sister chromatid cohesion, chromosome segregation, and gene regulation during…
Physiology of Sweating Sweating—or perspiration—is a vital autonomic thermoregulatory function mediated primarily by eccrine sweat glands distributed across the skin. These glands are innervated by sympathetic cholinergic fibers, which release acetylcholine to stimulate sweat production in response to elevated core body temperature, emotional stress, or hormonal fluctuations. The primary purpose of sweating is to maintain…
Pathophysiology and Molecular Genetics Krabbe disease is a severe, autosomal recessive lysosomal storage disorder caused by mutations in the GALCGALC gene (located on chromosome 14q31), which encodes the lysosomal enzyme galactosylceramidase (GALC). The deficiency of GALC leads to the failure of catabolizing galactosylceramide, a major component of myelin lipids. This results in two primary pathogenic…
Introduction and Pathophysiology Nutcracker syndrome (NCS), formally termed left renal vein entrapment syndrome, is a vascular disorder characterized by extrinsic compression of the left renal vein (LRV) between the abdominal aorta (AA) anteriorly and the superior mesenteric artery (SMA) posteriorly. This anatomical narrowing—termed the aortomesenteric pinch—occurs in approximately 5–10 mm at the LRV–aortic interface, with…
Overview Myoclonic Epilepsy with Ragged-Red Fibers (MERRF) is a rare, progressive, multisystem mitochondrial disorder primarily affecting the central and peripheral nervous systems and skeletal muscle. First described by Davies et al. in 1975, MERRF is classified among the mitochondrial encephalomyopathies and is characterized by the histopathological hallmark—ragged-red fibers (RRFs) visible on Gomori trichrome–stained skeletal muscle…
Updated with Current Evidence (2023–2024 Guidelines and Landmark Studies) 1. Introduction and Pathophysiology Diamond-Blackfan Anemia (DBA; OMIM #105650) is a rare, inherited bone marrow failure syndrome (IBMFS) characterized by a selective defect in erythroid progenitor cell development, resulting in pure red cell aplasia—i.e., profoundFailure of erythropoiesis without significant involvement of myeloid or megakaryocytic lineages. DBA…
Based on Current Evidence (2023–2024 Guidelines, ICSD-3, and Key Peer-Reviewed Literature) 1. Definition & Epidemiology Delayed Sleep/Wake Phase Disorder (DSPWD)—renamed in the International Classification of Sleep Disorders, 3rd Edition (ICSD-3) to emphasize its status as a clinical disorder rather than a variant of normal variation—is a circadian rhythm sleep-wake disorder (CirRD-SWDD) characterized by a persistent…
Definition & PathophysiologyMucus fishing syndrome (MFS) is a behavioral-ocular disorder characterized by repetitive, voluntary removal of filamentous mucus strands from the ocular surface—typically using fingers, cotton swabs, or other tools—despite lack of clinical indication. Though not an organic disease per se, MFS represents a maladaptive habit that perpetuates ocular surface inflammation and mucin hypersecretion via…
Tricuspid atresia (TA) is a cyanotic congenital heart defect characterized by the absence or complete occlusion of the tricuspid valve, preventing normal blood flow from the right atrium to the right ventricle. This condition occurs in approximately 0.5–1.2 per 10,000 live births, accounting for ~3–5% of all congenital heart diseases (PHI registry data, Circulation, 2023)….
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