#medical dictionary

• Achromatocyte — A pathologically degraded erythrocyte that has completely lost its hemoglobin content, appearing under the microscope as a pale, discolored, or empty cellular structure; a residual red blood cell (erythrocyte ghost) resulting from a severe hemolytic process or mechanical membrane trauma.
• Achromatopsic person — A person affected by achromatopsia, suffering from a total visual anomaly characterized by the congenital or acquired inability to distinguish colors, perceiving the environment exclusively in shades of white, black, and gray. As an adjective, the term describes an individual, an eye, or a visual system exhibiting this severe and rare form of total color blindness.
• Achromatopsic — Suffering from achromatopsia; characterized by the total inability to perceive and distinguish the colors of the visible spectrum, with the world being perceived exclusively in shades of gray, white, and black. As a noun, it designates a male individual diagnosed with this rare congenital condition, caused by a severe structural dysfunction of the cone photoreceptor cells in the retina.
• Achromatopsia — A congenital or acquired ophthalmological condition, genetic or neurological in nature, characterized by the total inability to perceive the colors of the visible spectrum. The affected subject distinguishes only shades of white, black, and gray (monochromatic vision), a state often accompanied by reduced visual acuity, extreme sensitivity to light (photophobia), and involuntary eye movements (nystagmus).
• Achromatosis — A generalized pathological condition characterized by the total absence or severe diminution of normal pigmentation within a tissue, organ, or the entire organism. In dermatology, the term describes severe states of cutaneous depigmentation (such as extreme forms of albinism or vitiligo universalis) where cells no longer produce melanin.
• Achromaturia — A pathological clinical condition manifested by the emission of completely colorless or pale urine, lacking normal urinary pigments (such as urochrome and urobilin). This phenomenon may indicate extreme dilution in diabetes insipidus, a severe inability of the kidneys to concentrate urine in advanced renal failure, or a massive and sudden intake of fluids.
• Achromasia — A general term designating the total absence of color or pigments within a structural medium. In medicine, it is synonymous with achromatopsia (total color blindness) or describes cellular and cutaneous depigmentation (lack of melanin); in optics, it defines the perfect correction of chromatic aberrations in a lens system.
• Acromegalic — Suffering from acromegaly; characterized by the excessive and disproportionate development of the body's extremities (hands, feet, facial bones, nose, jaw) due to the pathological hypersecretion of growth hormone (somatotropin) after the closure of epiphyseal plates. As a noun, it designates a male individual clinically diagnosed with this chronic neuroendocrine condition, most commonly triggered by a pituitary adenoma.
• Acromegalic — A synonymous variant of the adjective acromegal; relating to acromegaly, manifesting its symptoms, or affected by the hypersecretion of somatotropin. As a noun, the term defines a male individual presenting the clinical picture of the disease, marked by hypertrophy of the facial bones, hands, and feet secondary to a pituitary adenoma.
• Acromegaly — A chronic neuroendocrine disease caused by a pathological hypersecretion of growth hormone (somatotropin) and insulin-like growth factor (IGF-1) in adulthood, after the closure of epiphyseal growth plates. The condition is characterized by the exaggerated enlargement of skeletal extremities (hands, feet), hypertrophy of facial bones (prognatism, prominent brow ridges), soft tissue thickening, macroglossia, and secondary severe cardiac or metabolic dysfunctions.
• Acromelalgia — A rare clinical syndrome characterized by paroxysmal episodes of intense burning pain, pronounced redness (erythema), and increased local temperature in the extremities (hands and feet). Symptoms are typically triggered by exposure to heat or physical exertion and are caused by a vasomotor disorder of the peripheral microcirculation.
• Acromial — Pertaining to the acromion (the superior bony process of the scapula) or located in the upper shoulder region; referring to the anatomical, vascular, or nervous structures associated with this skeletal prominence.
• Acromicria — A rare pathological clinical condition, considered the opposite of acromegaly, characterized by the unusually small size and insufficient development of the body's extremities (hands, feet, facial bones). This structural syndrome is most often caused by congenital pituitary dysfunctions, diencephalic lesions, or severe secretory disorders of trophic hormones during growth.
• Achromia — The total congenital or acquired absence of normal pigmentation of the skin, hair, or other tissues, caused by the lack or destruction of melanocytes and melanin production. This general medical term covers manifestations such as generalized albinism or completely white patches occurring in advanced vitiligo.
• Acromion — A flattened and broadened bony projection forming the superior extremity of the scapular spine, articulating directly with the clavicle and representing the highest structural point of the shoulder skeleton.
• Acromionitis — An acute or chronic inflammatory pathological process localized at the level of the acromion or its immediately adjacent periarticular structures (such as the subacromial bursa and rotator cuff tendons). This structural condition is most frequently triggered by repeated microtraumas, occupational or athletic mechanical overuse, or localized degenerative phenomena, clinically manifesting through intense pain during arm elevation, partial functional impairment of the shoulder, localized edema, and acute tenderness upon palpation.
• Acromiotonia — A pathophysiological condition characterized by a state of marked muscular hypertonia, rigidity, or persistent muscular contracture localized strictly within the body's extremities (hands and feet). This complex neuromuscular phenomenon reflects a structural disruption of myotatic reflexes, typically encountered in pyramidal or extrapyramidal disorders, brainstem lesions, or central motor-neuron disturbances.
• Chromocenter — A microscopic nuclear structure formed by the fusion or aggregation of the pericentromeric heterochromatic regions (centromeres) of multiple chromosomes during cellular interphase. This dense structural formation, frequently observed within the salivary glands of certain insects (such as the polytene chromosomes of Drosophila), appears under the microscope as an intensely stainable central mass from which the euchromatic chromosomal arms radiate, lacking direct transcriptional activity in that zone.
• Achromatocyte — A pathological erythrocyte cell form or degraded stage of a red blood cell that has partially or completely lost its normal hemoglobin content, appearing under the microscope as a pale, semitransparent, or fully pigment-depleted cellular structure. This structural phenomenon typically occurs following severe intravascular hemolysis, mechanical cell membrane trauma, or intense osmotic alterations, leaving behind a residual membrane known in specialized literature as an erythrocyte ghost.
• Leukoderma — A congenital or acquired cutaneous pathological condition characterized by the total absence or severe and extensive diminution of normal skin pigmentation, manifesting as broad white patches or generalized depigmentation of the epidermis. This structural disorder is caused by the absence, destruction, or chronic metabolic dysfunction of melanocytes, leading to a complete halt in melanin production and resulting in extreme skin sensitivity to ultraviolet radiation.