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Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

38 results found
Article

Hemoglobinopathies

A hemoglobinopathy is a genetic disorder which alters the structure of hemoglobin 1. The result is reduced oxygen-carrying capacity of the blood to the tissues, and other sequelae. Clinical presentation Clinical presentation varies, is related to hypoxia, and characteristically includes the fo...
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Hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a multisystem thrombotic microangiopathic disease characterized by the triad of renal failure, hemolytic anemia and thrombocytopenia. It is the most common cause of renal failure in infancy and childhood requiring dialysis.  There are two forms of this syndrom...
Article

Hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a non-malignant but often-fatal disorder of immune dysregulation affecting multiple organs. It is also known as macrophage activation syndrome when occurring in the setting of a rheumatologic disorder. Epidemiology It typically affects infants and yo...
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Haglund syndrome

Haglund syndrome refers to the triad (Haglund triad) of: insertional Achilles tendinopathy retrocalcaneal bursitis Haglund deformity (i.e. posterosuperior calcaneal exostosis) Terminology Haglund syndrome is a painful condition of the heel and its diagnosis requires a combination with clini...
Article

Hajdu-Cheney syndrome

Hajdu-Cheney syndrome is a very rare connective tissue disorder with only 50 cases reported in the literature 7. Clinical presentation It is mostly diagnosed in adulthood or adolescence with the presence of a positive family history. There has been no link between severity of disease and age o...
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Hamatolunate impingement syndrome

Hamatolunate impingement is an uncommon cause of ulnar-sided wrist pain. The condition occurs most commonly in wrists where there is type II lunate morphology (existence of a medial facet on the distal lunate for articulation with the hamate). Repeated impaction of the opposing articular surface...
Article

Hamman syndrome

Hamman syndrome, also known as Macklin syndrome, refers to spontaneous pneumomediastinum along with subcutaneous emphysema. Epidemiology It is a rare entity most often encountered in young adults. It is a known entity peri- and postpartum 3. Clinical presentation The condition is most common...
Article

Hand-foot syndrome (chemotherapy)

Hand-foot syndrome, also known as palmar-plantar erythrodysaesthesia or Burgdorf reaction, is a benign, aseptic, self-limiting complication of many chemotherapeutic agents characterized by a widespread erythema, edema and ulceration of the hands and feet.  Causative drugs Many chemotherapeutic...
Article

Heerfordt syndrome

Heerfordt syndrome, also known as Heerfordt-Waldenström syndrome or uveoparotid fever, is a variant of sarcoidosis, comprising of: fever parotid enlargement facial palsy ocular involvement (anterior uveitis) Epidemiology The exact prevalence is unknown, as only isolated case reports exist....
Article

Heiner syndrome

The Heiner syndrome is a rare form of primary pulmonary hemosiderosis associated with an allergy to cow's milk. The syndrome includes: rectal blood loss with hypochromic microcytic anemia pulmonary infiltrates (often recurrent) hypoproteinemia See also pulmonary hemosiderosis
Article

HELLP syndrome

HELLP syndrome is a pregnancy-related condition and is an abbreviation for: haemolysis elevated liver enzymes and  low platelets It is considered a severe and life-threatening form of pre-eclampsia although it can occur without co-existing pre-eclampsia.  Epidemiology The estimated inciden...
Article

Hemiconvulsion-hemiplegia epilepsy syndrome

Hemiconvulsion-hemiplegia epilepsy syndrome (HHE) is a clinical syndrome of infancy or early childhood that is associated with seizures, cerebral hemiatrophy and transient or permanent epilepsy. It refers to the characteristic holohemispheric global atrophy of one hemisphere, that is independen...
Article

Hemifacial microsomia

Hemifacial microsomia (HFM) is the second most common congenital facial anomaly after cleft lip/palate. The condition may vary from mild to severe. Goldenhar syndrome has been described as a variant of HFM, in which vertebral anomalies and epibulbar dermoids were present. Terminology HFM is al...
Article

Hemihyperplasia

Hemihyperplasia, also known as hemihypertrophy, is asymmetry in size between the right and left of the body, more than can be attributed to normal variation. Terminology Hemihyperplasia is more scientifically correct than hemihypertrophy as the cells are hyperplastic rather than hypertrophied ...
Article

Hemimedullary syndrome

Hemimedullary syndrome, also known as Reinhold syndrome, occurs as a result of the occlusion of the ipsilateral vertebral artery proximal to the posterior inferior cerebellar artery and its anterior spinal artery branches 1-3. This situation causes lateral medullary infarct and medial medullary ...
Article

Hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a clinical syndrome defined by the presence of the following: liver disease dilation of pulmonary vasculature may involve pulmonary capillaries, pulmonary arteriovenous malformations, or pleural AVMs abnormalities in oxygenation elevation in the alveolar-ar...
Article

Hepatorenal syndrome

Hepatorenal syndrome refers to a form of acute kidney injury caused by changes in renal blood flow regulation due to liver pathology 1. Although the syndrome occurs mainly in cirrhotic livers it has been reported in patients with acute fulminant liver failure as well 1. Epidemiology The incide...
Article

Hereditary angiopathy with nephropathy, aneurysms, and muscle cramps syndrome

Hereditary angiopathy with nephropathy, aneurysms, and muscle cramps (HANAC) syndrome is an autosomal dominant monogenic COL4A1-related disorder. Epidemiology The exact prevalence is unknown. Clinical presentation The cardinal features of HANAC syndrome are helpfully described in the name of...
Article

Hereditary breast and ovarian cancer syndrome

Hereditary breast and ovarian cancer (HBOC) syndrome is caused by a mutation to either BRCA1 or BRCA2 genes. These patients have an increased risk of breast cancer, ovarian cancer, pancreatic cancer and prostate cancer. However, these gene mutations are not the only cause of hereditary breast ca...
Article

Hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a rare inherited disorder characterized by abnormal blood vessel formation in the skin, mucous membranes, and organs including the lungs, liver, and central nervous system. Epidemiology Worldwide prevalen...
Article

Hereditary multiple exostoses

Hereditary multiple exostoses, also known as diaphyseal aclasis or osteochondromatosis is an autosomal dominant condition, characterized by the development of multiple osteochondromas. Epidemiology Hereditary multiple exostoses demonstrate an autosomal dominant inheritance pattern, with incomp...
Article

Hereditary non-polyposis colorectal cancer

Hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is an autosomal dominant condition which predisposes to a host of malignancies, including colorectal carcinoma. It is considered the most frequent form of hereditary colorectal cancer. Diagnosis requires evaluation...
Article

Hereditary renal cancer syndromes

Despite the vast majority of renal cancers being sporadic, there are a number of hereditary renal cancer syndromes: von Hippel Lindau syndrome: predominantly clear cell type tuberous sclerosis: predominantly clear cell type (also associated with angiomyolipoma) hereditary paraganglioma-pheoch...
Article

Herlyn-Werner-Wunderlich syndrome

Herlyn-Werner-Wunderlich (HWW) syndrome, is a rare anomaly characterized by Müllerian duct anomalies (MDA) associated with mesonephric duct anomalies 3. This entity is also known as obstructed hemivagina and ipsilateral renal anomaly (OHVIRA). It is not to be confused with the Wunderlich syndrom...
Article

Hermansky-Pudlak syndrome

Hermansky-Pudlak syndrome (HPS) is a rare syndrome which consists of: oculocutaneous hypopigmentation (albinism) platelet dysfunction  abnormal storage of autofluorescent pigment (ceroid or lipofuscin)  typically occurs within lysosomal organelles of the cells of multiple organs and the reti...
Article

Heterotaxy syndrome

Heterotaxy syndrome or situs ambiguus (also commonly, but etymologically less correctly, spelled situs ambiguous) is a disturbance in the usual left-right distribution of the thoracic and abdominal organs that does not entirely correspond to the complete mirror image (situs inversus). It occurs...
Article

Heyde syndrome

Heyde syndrome is an association between aortic valve stenosis and gastrointestinal hemorrhage. The etiology of the gastrointestinal bleeding in this setting is uncertain, but it is thought to be related to intestinal angiodysplasia. The strength of this association independent of age-related d...
Article

HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) is commonly seen in patients with HIV/AIDS and leads to end-stage renal disease (ESRD). The diagnosis is not imaging-based and must be confirmed by renal biopsy. Epidemiology HIVAN is seen in patients at advanced stages of HIV and AIDS, but it can also be see...
Article

Horizontal gaze palsy with progressive scoliosis

Horizontal gaze palsy with progressive scoliosis (HGPPS) is a rare autosomal recessive disease. Clinical presentation Abnormal horizontal gaze while normal vertical gaze and kyphoscoliosis. Horizontal gaze requires the action of ipsilateral abducent nerve and contralateral oculomotor nerve and...
Article

Hunter syndrome

Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II) is a rare genetic mucopolysaccharidosis disorder characterized by specific clinical features 1. Epidemiology Hunter syndrome is an X-linked recessive disease and therefore much more common in males. It is a rare disorder wit...
Article

Hurler syndrome

Hurler syndrome is one of the mucopolysaccharidoses (MPS type I). Epidemiology The estimated incidence is ~1:100,000. Clinical presentation It manifests in the first years of life with intellectual disability, corneal clouding, deafness, and cardiac disease. Death usually occurs within the f...
Article

Hydrolethalus syndrome

Hydrolethalus syndrome is a rare lethal genetic syndrome characterized by multiple developmental defects of fetus which include  midline malformations cleft lip + / - palate CNS malformations fetal hydrocephalus agenesis of the corpus callosum Dandy-Walker malformation absent midline stru...
Article

Hyperimmunoglobulin IgE syndrome

Hyperimmunoglobulin E (hyper IgE) syndrome (HIES), also known as Job syndrome, consists of a heterogeneous group of complex hereditary combined B- and T-cell immune deficiency diseases characterized by recurrent Staphylococcus aureus chest infections, characteristic coarse facial appearance and ...
Article

Hyperparathyroidism-jaw tumor syndrome

Hyperparathyroidism-jaw tumor syndrome is an extremely rare condition where a gene mutation results in hyperparathyroidism in association with both benign and malignant tumors, most notably, tumors in the mandible or maxilla 2. Epidemiology Approximately 200 cases have been reported in the med...
Article

Hypomelanosis of Ito

Hypomelanosis of Ito, also known as incontinentia pigmenti achromians, is the third most frequent phakomatosis, involving a wide spectrum of defects in multiple organ systems. Epidemiology The prevalence is unknown, being reported as between 1 per 8000 patients in a general pediatric hospital ...
Article

Hypophosphatasia

Hypophosphatasia refers to a rare metabolic disorder characterized by deficient serum alkaline phosphatase activity. The effects of hypophosphatasia are primarily seen in the skeletal system. The condition has marked variation in clinical expression (see subtypes). Epidemiology The true incide...
Article

Hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a cyanotic congenital cardiac anomaly where affected individuals can have profound cyanosis and cardiac failure. It is one of the commonest causes for a neonate to present with congestive cardiac failure and the 4th most frequent cardiac anomaly to mani...
Article

Hypothenar hammer syndrome

Hypothenar hammer syndrome occurs from trauma to the distal ulnar artery or proximal portion of superficial palmar arch as a result of repetitive trauma to the hypothenar eminence. Originally described in patients using hammers and screwdrivers, it is also seen in various athletes such as basket...

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