DISORDERS
Some Disorders of Human Development
| Anencephaly | Lack of a forebrain due to failure of the cranial roof to form, leaving the forebrain exposed. The exposed tissue dies, and the fetus is born (or stillborn) with only a brainstem. Live-born anencephalic infants are very short-lived. |
| Cleft lip and palate | Failure of the right and left sides of the lip or palate to fuse medially, resulting in abnormal facial appearance, defective speech, and difficulty suckling. |
| Clubfoot (talipes) | Deformity of the foot involving an ankle bone, the talus. The sole of the foot is commonly turned medially, and as a child grows, he or she may walk on the ankles rather than on the soles. |
| Hydrocephalus | Abnormal accumulation of cerebrospinal fluid in the brain. When it occurs in the fetus, the cranial bones separate, the head becomes abnormally large, and the face looks disproportionately small. May reduce the cerebrum to a thin shell of nervous tissue. Fatal for about half of patients but can be treated by inserting a shunt that drains fluid from the brain to a vein in the neck. |
| Meromelia | Partial absence of limbs (as in fig. 4.15), such as the lack of some digits, a hand, or a forearm. Complete absence of a limb is amelia. |
Integumentary System
| Acne | Inflammation of the sebaceous glands, especially beginning at puberty; follicle becomes blocked with keratinocytes and sebum and develops into a blackhead (comedo) composed of these and bacteria; continued inflammation of follicle results in pus production and pimples. |
| Dermatitis | Any inflammation of the skin, typically marked by itching and redness; often contact dermatitis, caused by exposure to toxins such as poison ivy. |
| Eczema | Itchy, red, “weeping” skin lesions caused by an allergy, usually beginning before age 5; may progress to thickened, leathery, darkly pigmented patches of skin. |
| Psoriasis | Recurring, reddened plaques covered with silvery scale; sometimes disfiguring; possibly caused by an autoimmune response; runs in families |
| Ringworm | A fungal infection of the skin (not a worm) that sometimes grows in a circular pattern; common in moist areas such as the axilla, groin, and foot (athlete’s foot). |
| Rosacea | A red rashlike area, often in the area of the nose and cheeks, marked by fine networks of dilated blood vessels; worsened by hot drinks, alcohol, and spicy food. |
| Warts | Benign, elevated, rough lesions caused by human papillomaviruses (HPV). Common warts appear most frequently in late childhood on the fingers, elbows, and other areas of skin subject to stress. Plantar warts occur on the soles and venereal warts on the genitals. Warts can be treated by freezing with liquid nitrogen, electric cauterization (burning), laser vaporization, surgical excision, and some medicines such as salicylic acid. |
Structural Disorders of Bone
| Acromegaly | A result of adult growth hormone hypersecretion, resulting in thickening of the bones and soft tissues, especially noticeable in the face, hands, and feet. |
| Osteitis deformans | Excessive osteoclast proliferation and bone resorption, with osteoblasts attempting to compensate by depositing extra bone. This results in rapid, disorderly bone remodeling and weak, deformed bones. Osteitis deformans usually passes unnoticed, but in some cases it causes pain, disfiguration, and fractures. It is most common in males over the age of 50. |
| Osteomalacia | Adult form of rickets, most common in poorly nourished women who have had multiple pregnancies. Bones become softened, deformed, and more susceptible to fractures. |
| Rickets | Defective mineralization of bone in children, usually as a result of insufficient sunlight or vitamin D, sometimes due to a dietary deficiency of calcium or phosphate or to liver or kidney diseases that interfere with calcitriol synthesis. Causes bone softening and deformity, especially in the weight-bearing bones of the lower limbs. |
Disorders of the Axial Skeleton
| Cleft palate | Failure of the palatine processes of the maxilla to fuse during fetal development, resulting in a fissure connecting the oral and nasal cavities; often accompanied by cleft lip. Causes difficulty for an infant in nursing. Can be surgically corrected with good cosmetic results. |
| Craniosynostosis | Premature closure of the cranial sutures within the first two years after birth, resulting in skull asymmetry, deformity, and sometimes mental retardation. Cause is unknown. Surgery can limit brain damage and improve appearance. |
| Spinal stenosis | Abnormal narrowing of the vertebral canal or intervertebral foramina caused by hypertrophy of the vertebral bone. Most common in middleaged and older people. May compress spinal nerves and cause low back pain or muscle weakness |
| Spondylosis | A defect of the laminae of the lumbar vertebrae. Defective vertebrae may shift anteriorly, especially at the L5 to S1 level. Stress on the bone may cause microfractures in the laminae and eventual dissolution of the laminae. May be treated by nonsurgical manipulation or by surgery, depending on severity. |
Disorders of the Appendicular Skeleton
| Avulsion | A fracture in which a body part, such as a finger, is completely torn from the body, as in many accidents with farm and factory machinery. The term can also refer to nonosseous structures such as the avulsion of an ear. |
| Calcaneal (heel) spurs | Abnormal outgrowths of the calcaneus. Often results from high-impact exercise such as aerobics and running, especially if done with inappropriate footwear. Stress on the plantar aponeurosis (a connective tissue sheet in the sole of the foot) stimulates exostosis, or growth of a bony spur, and can cause severe foot pain. |
| Colles fracture | Pathologic fracture at the distal end of the radius and ulna, often occurring when stress is placed on the wrist (as in pushing oneself up from an armchair) and the bones have been weakened by osteoporosis. |
| Epiphyseal fracture | Separation of the epiphysis from the diaphysis of a long bone. Common in children and adolescents because of their cartilaginous epiphyseal plates. May present a threat to normal completion of bone growth. |
| Pes planus | “Flat feet” or “fallen arches” (absence of visible arches) in adolescents and adults. Caused by stretching of plantar ligaments due to prolonged standing or excess weight. |
Disorders of the Joints
| Dislocation (luxation) | Displacement of a bone from its normal position at a joint, usually accompanied by a sprain of the adjoining connective tissues. Most common at the fingers, thumb, shoulder, and knee. |
| Gout | A hereditary disease, most common in men, in which uric acid crystals accumulate in the joints and irritate the articular cartilage and synovial membrane. Causes gouty arthritis, with swelling, pain, tissue degeneration, and sometimes fusion of the joint. Most commonly affects the great toe. |
| Strain | Painful overstretching of a tendon or muscle without serious tissue damage. Often results from inadequate warm-up before exercise. |
| Subluxation | Partial dislocation in which two bones maintain contact between their articular surfaces. |
| Synovitis | Inflammation of a joint capsule, often as a complication of a sprain. |
Disorders of the Muscular System
| Charley horse | Slang for any painful tear, stiffness, and blood clotting in a muscle caused by contusion (a blow to the muscle causing hemorrhaging). |
| Contracture | Abnormal muscle shortening not caused by nervous stimulation. Can result from a persistence of calcium in the sarcoplasm after stimulation or from contraction of scar tissue. |
| Crush syndrome | A shocklike state following the massive crushing of muscles, associated with a high and potentially fatal fever, cardiac irregularities caused by K+ released from the injured muscles, and kidney failure caused by blockage of the renal tubules with myoglobin released by the traumatized muscle. Myoglobin in the urine (myoglobinuria) is a common sign. |
| Delayed onset muscle soreness | Pain and stiffness felt from several hours to a day after strenuous exercise. Associated with microtrauma to the muscles, with disrupted Z discs, myofibrils, and plasma membranes, and with elevated blood levels of myoglobin and enzymes released by damaged muscle fibers. |
Some Disorders of the Spinal Cord and Spinal Nerves
| Guillain-Barre syndrome | An acute demyelinating nerve disorder often triggered by viral infection, resulting in muscle weakness, elevated heart rate, unstable blood pressure, shortness of breath, and sometimes death from respiratory paralysis |
| Neuralgia | General term for nerve pain, often caused by pressure on spinal nerves from herniated intervertebral discs or other causes |
| Paresthesia | Abnormal sensations of prickling, burning, numbness, or tingling; a symptom of nerve trauma or other peripheral nerve disorders |
| Peripheral neuropathy | Any loss of sensory or motor function due to nerve injury; also called nerve palsy |
| Rabies (hydrophobia) | A disease usually contracted from animal bites, involving viral infection that spreads via somatic motor nerve fibers to the CNS and then out of the CNS via autonomic nerve fibers, leading to seizures, coma, and death; invariably fatal if not treated before CNS symptoms appear |
| Spinal meningitis | Inflammation of the spinal meninges due to viral, bacterial, or other infection |
Some Disorders Associated with the Brain and Cranial Nerves
| Cerebral palsy | Muscular incoordination resulting from damage to the motor areas of the brain during fetal development, birth, or infancy; causes include prenatal rubella infection, drugs, and radiation exposure; oxygen deficiency during birth; and hydrocephalus |
| Concussion | Damage to the brain typically resulting from a blow, often with loss of consciousness, disturbances of vision or equilibrium, and short-term amnesia |
| Encephalitis | Inflammation of the brain, accompanied by fever, usually caused by mosquito-borne viruses or herpes simplex virus; causes neural degeneration and necrosis; can lead to delirium, seizures, and death |
| Epilepsy | Disorder causing sudden, massive discharge of neurons (seizures) resulting in motor convulsions, sensory and psychic disturbances, and often impaired consciousness; may result from birth trauma, tumors, infections, drug or alcohol abuse, or congenital brain malformation |
| Migraine headache | Recurring headaches often accompanied by nausea, vomiting, dizziness, and aversion to light, often triggered by such factors as weather changes, stress, hunger, red wine, or noise; more common in women and sometimes hereditary |
| Schizophrenia | A thought disorder involving delusions, hallucinations, inappropriate emotional responses to situations, incoherent speech, and withdrawal from society, resulting from hereditary or developmental abnormalities in neural networks |
Some Disorders of the Autonomic Nervous System
| Achalasia of the cardia | A defect in autonomic innervation of the esophagus, resulting in impaired swallowing, accompanied by failure of the lower esophageal sphincter to relax and allow food to pass into the stomach. (The region of the stomach at its junction with the esophagus is called the cardia.) Results in enormous dilation of the esophagus and inability to keep food down. Most common in young adults; cause remains poorly understood. |
| Horner syndrome | Chronic unilateral pupillary constriction, sagging of the eyelid, withdrawal of the eye into the orbit, flushing of the skin, and lack of facial perspiration. Results from lesions in the cervical ganglia, upper thoracic spinal cord, or brainstem that interrupt sympathetic innervation of the head. |
Some Sensory Disorders
| Ageusia | Loss of the sense of one or more taste modalities, often due to damage to the hypoglossal nerve (loss of bitter taste) or facial nerve (loss of sweet, sour, and salty tastes) |
| Color blindness | Inability to distinguish certain colors from each other, such as green and orange, due to a hereditary lack of one of the three types of cones. A sex-linked recessive trait that affects more men than women. |
| Meniere disease | A disorder of proprioception in which one experiences episodes of vertigo (dizziness) often accompanied by nausea, tinnitus, and pressure in the ears. Usually accompanied by progressive hearing loss. |
| Paresthesia | Feelings of numbness, prickling, tingling, heat, or other sensations in the absence of stimulation; a symptom of nerve injuries and other neurological disorders. |
| Tinnitus | Perception of imaginary sounds such as whistling, buzzing, clicking, or ringing in the ear. May be temporary or permanent, intermittent or constant; typically associated with hearing loss in the high frequencies. May result from cochlear damage, aspirin or other drugs, ear infections, Ménière disease, or other causes. |
Disorders of the Endocrine System
| Addison disease | Hyposecretion of adrenal glucocorticoids or mineralocorticoids, causing hypoglycemia, hypotension, weight loss, weakness, loss of stress resistance, darkening of the skin, and potentially fatal dehydration and electrolyte imbalances |
| Adrenogenital syndrome | Hypersecretion of adrenal androgens. Prenatal hypersecretion can cause girls to be born with masculinized genitalia and to be misidentified as boys. In children, it often causes enlargement of the penis or clitoris and premature puberty. In women, it causes masculinizing effects such as increased body hair, beard growth, and deepening of the voice. |
| Congenital hypothyroidism | Thyroid hyposecretion present from birth, resulting in stunted physical development, thickened facial features, low body temperature, lethargy, and irreversible brain damage in infancy |
| Cushing syndrome | Cortisol hypersecretion resulting from overactivity of the adrenal cortex. Results in disruption of carbohydrate and protein metabolism, hyperglycemia, edema, loss of bone and muscle mass, and sometimes abnormal fat deposition in the face or between the shoulders. |
| Endemic goiter | Enlargement of the thyroid gland, combined with thyroid hormone hyposecretion, as a result of dietary iodine deficiency. |
| Myxedema | A result of severe or prolonged adult hypothyroidism, characterized by low metabolic rate, sluggishness and sleepiness, weight gain, constipation, hypertension, dry skin and hair, abnormal sensitivity to cold, and tissue swelling. |
| Pituitary dwarfism | Abnormally short stature, with a normal proportion of limbs to trunk, resulting from growth hormone hyposecretion in childhood. |
| Pituitary gigantism | Abnormally tall stature, with a normal proportion of limbs to trunk, resulting from growth hormone hypersecretion in childhood. |