Alphabetical list of conditions

Achondroplasia

An AD (80% new mutation rate) skeletal dysplasia due to impaired enchondral bone growth.

Acquired immune deficiency syndrome

Widespread use of highly active antiretroviral therapy (HAART) has significantly changed the patterns of presentation of HIV-related disease in adults in developed nations. Opportunistic infections are less common, whereas non-AIDS-defining cancers and disorders related to immune reconstitution are being seen with greater frequency. In nondeveloped countries without widespread access to HAART, the profile of AIDS-related diseases has changed little.

Acquired immune deficiency syndrome (AIDS) in children

The majority are due to transmission from an infected mother. Infection from transfusions (in the neonatal period or because of diseases such as thalassaemia and haemophilia) is rare in the West but still occurs in developing countries. 50% of those infected congenitally will present in the first year of life. Prognostic factors: severity of disease in the mother, age of onset, severity at onset. AIDS in children differs from AIDS in adults in the following ways:

• 1.

  Shorter incubation period.

• 2.

  More likely to have serious bacterial infections or CMV.

• 3.

  More commonly develop pulmonary lymphoid hyperplasia (PLH) and lymphocytic interstitial pneumonia (LIP).

• 4.

  Almost never develop Kaposi sarcoma.

• 5.

  Less likely to be infected with Toxoplasma , TB, Cryptococcus and Histoplasma .

• 6.

  Two patterns of presentation and progression can be recognized:

  • (a)

    In the first year of life—serious infections and encephalopathy. Poor prognosis.

  • (b)

    Preschool and school age—bacterial infections and lymphoid tissue hyperplasia. Survival is longer, to adolescence.

Acromegaly

Caused by a pituitary adenoma producing excess growth hormone. Main imaging manifestations are musculoskeletal.

Alkaptonuria

The absence of homogentisic acid oxidase leads to the accumulation of homogentisic acid and its excretion in sweat and urine. The majority of cases are AR.

Alpha-1 antitrypsin deficiency

Hereditary metabolic disorder; main manifestations are in the lungs and liver.

• 1.

  Lungs—panlobular emphysema with a basal predominance. Commonest clinical presentation, usually in young/middle aged adults. Bronchiectasis may also be seen.

• 2.

  Liver—cirrhosis in 15% of adult patients. May also cause cholestasis in neonates.

• 3.

  Aneurysms—especially intracranial.

• 4.

  Subcutaneous necrotizing panniculitis.

• 5.

  Other associations—pancreatitis, IBD, vasculitis (e.g. Wegener's), hypothyroidism, glomerulonephritis.

Amyloidosis

Group of diseases characterized by deposition of amyloid proteins which can occur in any organ or tissue. Usually presents in older adults. Many different types:

• 1.

  Systemic—involves multiple organs or tissues.

  • (a)

    Amyloid light chain (AL)—produced by an abnormal clonal population of plasma cells, e.g. in multiple myeloma, B-cell lymphoma or Waldenström's macroglobulinaemia.

  • (b)

    Serum amyloid A (AA)—secondary to chronic inflammatory disorders, e.g. rheumatoid arthritis, Crohn's disease, seronegative spondyloarthropathies, Sjögren's syndrome, dermatomyositis, vasculitis, SLE, familial Mediterranean fever, chronic infections such as osteomyelitis, TB or bronchiectasis, and some tumours (e.g. RCC).

  • (c)

    Amyloid transthyretin (ATTR)—two subtypes:

    • (i)

      Wild-type ATTR—also known as senile systemic amyloidosis. Almost exclusively in older men; mainly involves the heart ± carpal tunnel syndrome.

    • (ii)

      Mutant ATTR— also known as familial amyloid polyneuropathy. Hereditary (AD), usually presenting in young adults. Primarily involves peripheral and autonomic nerves.

  • (d)

    Amyloid β ₂ microglobulin (Aβ ₂ M)—seen in patients on long-term haemodialysis; mainly involves joints.

• 2.

  Localized—less common. Amyloid protein (typically AL) is deposited in a specific organ or tissue, most commonly respiratory tract, skin or urinary tract. Not associated with a generalized plasma cell dyscrasia. Cerebral amyloid angiopathy and Alzheimer's disease can also be considered as localized forms of amyloidosis (Aβ).

Ankylosing spondylitis

A seronegative spondyloarthropathy manifesting as an inflammatory arthritis affecting the sacroiliac joints and entire spine, eventually resulting in ankylosis. Onset 20–40 years; M>F.

Asbestos-related diseases

Lung and/or pleural disease caused by the inhalation of asbestos fibres. Long latency (>20–30 years) between exposure and lung/pleural disease. Pleural disease alone in 50%; pleura + lung disease 40%; lung disease alone 10%.

Behçet's disease

Chronic multisystem vasculitis involving vessels of variable size. Most common in young adult men, especially in eastern Mediterranean and eastern Asia. Presents clinically with oral and genital ulcers, ocular inflammation (e.g. uveitis and retinal vasculitis) and skin lesions (e.g. erythema nodosum). Imaging features include:

• 1.

  Venous thrombosis—commonest feature; can involve lower and upper limb veins, SVC, IVC, hepatic, portal and renal veins. SVC obstruction can also be caused by fibrosing mediastinitis.

• 2.

  Arteritis—can involve the aorta, aortic root, pulmonary arteries, coronary and peripheral arteries (femoral, subclavian and popliteal), causing characteristic saccular aneurysms, stenoses and occlusions. Pulmonary artery aneurysms in particular are highly suggestive.

• 3.

  Cardiac—pericarditis, myocarditis, endocarditis, myocardial infarction, endomyocardial fibrosis, intracardiac thrombosis.

• 4.

  Lungs—pulmonary emboli, infarcts and haemorrhage due to vasculitis, ± pleural effusions or nodules. Airway ulceration and occlusion can rarely be seen.

• 5.

  GI tract—ulcers are the typical feature, most common in the ileocaecal region. On CT/MRI there is mural thickening ± perforation or fistulation ± mesenteric fat wrapping, mimicking Crohn's disease (though perforation is more common in Behçet's and strictures are less common). Inflammatory polypoid lesions can also be seen.

• 6.

  Kidneys—glomerulonephritis, renal failure, infarcts, amyloidosis.

• 7.

  CNS—focal T2 hyperintense lesions with variable enhancement; brainstem > basal ganglia > thalamus > cerebral white matter and spinal cord. In atypical cases these may appear mass-like. Dural venous sinus thrombosis and cerebral arterial aneurysms/occlusions can also occur.

• 8.

  Rhinosinusitis ± bone erosions.

• 9.

  Arthritis—usually a subacute self-limiting nondeforming oligoarthropathy, most commonly involving the knee, ankle and SIJs. Manifests as periarticular osteopenia, soft-tissue swelling and joint space narrowing ± erosions.

• 10.

  Myositis—rare. Diffuse, patchy or nodular involvement.

Birt-Hogg-Dubé syndrome

Hereditary (AD) disorder characterized by:

• 1.

  Multiple lung cysts with a lower lobe predominance ± pneumothoraces.

• 2.

  Multiple bilateral renal tumours—especially oncocytomas and chromophobe RCCs.

• 3.

  Skin features—especially fibrofolliculomas (hair follicle hamartomas).

• 4.

  Other possible associations—benign and malignant tumours of the breast, colon, skin, lung, thyroid, parathyroid, parotid, peripheral nerves and fat (lipomas).

Blue rubber bleb naevus syndrome

Rare syndrome characterized by multiple venous malformations. On MRI, these lesions are markedly T2 bright and show avid homogeneous enhancement ± thrombi and phleboliths. Any part of the body can be involved; common sites include:

• 1.

  Skin—commonest site, giving rise to the so-called ‘blue rubber bleb’ naevi. Usually visible at birth.

• 2.

  GI tract—very common, especially in the small bowel; causes GI bleeding ± intussusception.

• 3.

  Musculoskeletal—skin lesions may extend into underlying muscles, bones and/or joints. Lesions can also arise from within deep soft tissues. Joint involvement can cause recurrent haemarthrosis and secondary arthritis. Bone involvement can cause cortical remodelling or focal lytic lesions. Limb overgrowth, undergrowth or bowing may also be seen.

• 4.

  Others—e.g. solid abdominal viscera, lung, heart, head and neck.

Carney complex

Hereditary (AD) multiple endocrine neoplasia syndrome, characterized by:

• 1.

  Skin lesions—pigmented spots, blue naevi, cutaneous myxomas.

• 2.

  Cardiac myxomas—often multiple.

• 3.

  Breast myxomas (in women and men), ductal adenomas and myxoid fibroadenomas.

• 4.

  Endocrine tumours:

  • (a)

    Pituitary hyperplasia or adenoma—secreting growth hormone or prolactin.

  • (b)

    Thyroid cysts, adenomas or carcinoma.

  • (c)

    Primary pigmented nodular adrenocortical disease—causes Cushing's syndrome.

  • (d)

    Testicular tumours—especially large cell calcifying Sertoli cell tumours (microcalcification is characteristic).

  • (e)

    Ovarian cysts, cystadenoma or teratoma.

• 5.

  Psammomatous melanotic schwannoma—can arise anywhere in the CNS or PNS; commonest sites are the GI tract (including liver), paraspinal sympathetic chain and chest wall. Melanin content may cause T1 hyperintensity and T2 hypointensity on MRI. Often calcified.

• 6.

  Osteochondromyxomas of bone—most common in the diaphysis of long bones (tibia and radius) and sinonasal bones. Variable appearances—may be well-defined or permeative, lytic or mixed density.

Carney triad

Rare syndrome, most common in young women. Characterized by the triad of:

• 1.

  Extraadrenal paraganglioma—e.g. retroperitoneal, mediastinal, intraspinal, carotid body.

• 2.

  GIST—usually gastric, often multifocal.

• 3.

  Pulmonary chondroma—lung nodule containing chondroid calcification. Usually multiple.

Chagas disease

Tropical protozoan infection ( Trypanosoma cruzi ) endemic in Central and South America, transmitted by triatomine insects. Characteristic imaging features mostly result from chronic infection, and include:

• 1.

  Myocarditis—acute and chronic phase, resulting in dilated cardiomyopathy. On MRI, myocardial thinning is typically seen in the apex and inferolateral wall with midwall or subepicardial LGE ± apical aneurysm formation.

• 2.

  GI tract dysmotility and dilatation—especially affecting the oesophagus (mimicking achalasia), but large and small bowel can also be involved. Always consider Chagas disease in young patients from endemic areas with diffuse oesophageal dilatation (megaoesophagus) and cardiomegaly.

• 3.

  Ureteric dilatation—occasionally.

• 4.

  CNS—meningoencephalitis can rarely occur if a chronically infected patient becomes immunocompromised. MRI shows multiple enhancing brain and spinal cord lesions.

Churg-strauss syndrome

Also known as eosinophilic granulomatosis with polyangiitis. Small–medium vessel vasculitis, most common in young–middle-aged adults. Nearly all patients have asthma and peripheral eosinophilia. Other clinical features include mononeuritis multiplex, skin rash/purpura, arthralgia and glomerulonephritis. Imaging features include:

• 1.

  Lungs—most common site. Transient/migratory peripheral multifocal patchy consolidation and GGO ± interlobular septal thickening ± noncavitary nodules ± bronchial wall thickening or dilatation ± small pleural effusions.

• 2.

  Heart—common cause of mortality. Pericarditis, valve insufficiency, myocardial infarction or endomyocarditis ± intracardiac thrombosis can occur. MRI may show mural LGE with variable patterns.

• 3.

  Allergic rhinosinusitis ± polyposis.

• 4.

  GI tract—eosinophilic gastroenteritis/oesophagitis, vasculitic bowel ischaemia (± perforation or stricture formation), GI bleeding, peritonitis/ascites, omental granulomatous nodules or haematoma.

• 5.

  HPB—hepatic artery aneurysms and infarcts, Budd-Chiari syndrome, eosinophilic hepatitis, acalculous eosinophilic cholecystitis, pancreatitis.

• 6.

  CNS—infarcts, haemorrhage or, rarely, granulomatous masses of the meninges or choroid plexus.

• 7.

  Orbits—optic neuritis, central retinal artery occlusion, inflammatory pseudotumour.

Cleidocranial dysplasia

AD. One-third are new mutations.

Coeliac disease

Common autoimmune disease affecting the GI tract, triggered by gluten intolerance. Treatment is a gluten-free diet; patients who do not respond to this are classified as having refractory disease and are at higher risk of complications. Imaging features include:

• 1.

  Dilated and fluid-filled small bowel with reversal of jejunoileal fold patterns ± transient intussusceptions. In severe refractory cases mural thickening and ulceration can be seen (ulcerative jejunoileitis), which can lead to haemorrhage, perforation, stricture formation and lymphoma.

• 2.

  Mesenteric lymphadenopathy is common. Rarely, in refractory disease, nodes may cavitate ± fat–fluid levels (cavitating mesenteric lymph node syndrome).

• 3.

  Increased risk of small bowel T cell lymphoma (especially terminal ileum; only in those with refractory disease) and adenocarcinoma (especially jejunum), as well as oesophageal SCC.

Extraintestinal associations include:

• 1.

  Splenic atrophy and hyposplenism—often accompanies cavitating mesenteric lymph node syndrome.

• 2.

  Other autoimmune disorders—autoimmune hepatitis, PBC, sclerosing cholangitis, type 1 diabetes, autoimmune thyroiditis, Sjögren's syndrome.

• 3.

  Cardiovascular—pericardial effusion, autoimmune myocarditis, cardiomyopathy, thromboembolism, accelerated atherosclerosis.

• 4.

  Dermatitis herpetiformis—papulovesicular skin rash.

• 5.

  Osteopenia and osteomalacia.

• 6.

  Lane-Hamilton syndrome—coeliac disease + idiopathic pulmonary haemosiderosis.

• 7.

  CEC syndrome—coeliac disease + bilateral occipital lobe calcifications ± epilepsy.

Cushing's syndrome

Cushing's syndrome results from increased endogenous or exogenous cortisol. Causes include:

• 1.

  Iatrogenic—high doses of corticosteroids. Most common cause.

• 2.

  Pituitary disease (Cushing's disease)—typically due to a microadenoma, which may be hard to visualize on MRI due to its small size. Both adrenals usually appear hyperplastic.

• 3.

  Adrenal disease—adenoma or carcinoma. The contralateral adrenal appears atrophic.

• 4.

  Ectopic ACTH—e.g. from lung cancer.

Cutis laxa

Heterogeneous group of rare inherited and acquired disorders characterized by loose and redundant skin with reduced elasticity. Other elastic tissues can also be involved, resulting in:

• 1.

  Lungs—emphysema, bronchiectasis.

• 2.

  Abdominal hernias—including hiatus hernia.

• 3.

  Diverticulosis—of the pharynx, GI tract and urinary tract.

• 4.

  Arterial aneurysms and pulmonary artery stenosis.

Cystic fibrosis

AR condition, with carrier rate of 1:25 in Caucasians, affecting 1:2000 live births. Basic defect is of highly viscid secretions. Main complications are pulmonary.

Cysticercosis

Parasitic infection caused by the pork tapeworm Taenia solium ; endemic in Central and South America, Africa and Asia. Cysticerci may involve any tissue or organ, most commonly:

• 1.

  Soft tissues—especially subcutaneous and intramuscular. Usually seen in the chronic calcified stage, as multiple discrete rice/cigar-shaped soft-tissue calcifications.

• 2.

  CNS (neurocysticercosis)—usually involves the brain but the spine, eyes and pituitary may also be involved. Lesions can be seen in subarachnoid spaces, brain parenchyma and ventricles. Complications include arachnoiditis, encephalitis, hydrocephalus (especially if ventricular involvement) and stroke (if vascular involvement). Lesions pass through four stages, each of which has a characteristic appearance:

  • 1.

    Vesicular (viable)—small nonenhancing cyst, often with a characteristic eccentric ‘dot’ (scolex). If subarachnoid in location, may be large and clustered (racemose) without a scolex, mimicking an arachnoid cyst.

  • 2.

    Colloidal (early degeneration)—cyst shows ring enhancement with surrounding oedema. Scolex may also enhance. This stage is often triggered by initiating treatment. Seizures are most common in this stage.

  • 3.

    Granular (late degeneration)—enhancing wall retracts, becomes thicker and starts becoming calcified. May show solid enhancement. Variable oedema.

  • 4.

    Calcified (dead)—small nodular calcification with no fluid, oedema or enhancement.

Down's syndrome (trisomy 21)

Ehlers-danlos syndrome (EDS)

A group of hereditary collagen disorders; many subtypes of varying severity. General clinical features include skin hyperelasticity and fragility, joint hypermobility and blood vessel fragility resulting in bleeding tendency. General imaging features include:

• 1.

  Soft tissues—subcutaneous calcification (due to fat necrosis) and heterotopic ossification.

• 2.

  Joint instability due to ligament laxity—can manifest as dislocations, joint effusions and haemarthroses, abnormal angulations, atlantoaxial and craniocervical instability, pes planus, early osteoarthritis.

• 3.

  Tendinopathy ± tendon rupture.

• 4.

  Spine—kyphoscoliosis, spondylolisthesis, dural ectasia.

• 5.

  Abdominal and diaphragmatic hernias, pelvic floor prolapse, visceroptosis.

• 6.

  GI tract—diverticula, dysmotility and dilatation, gastric volvulus and reflux.

• 7.

  Mitral valve prolapse.

• 8.

  Bladder diverticula.

Endometriosis

Common disorder characterized by ectopic endometrial tissue outside the uterus. Nearly always occurs in premenopausal women. Cyclical (catamenial) symptoms are characteristic. Endometriotic deposits may be:

• 1.

  Cystic (endometrioma)—usually unilocular with diffuse low-level echoes on US ± echogenic avascular foci adherent to the wall. On MRI, the contents show uniform T1 hyperintensity and reduced T2 signal (uniform or layered). The cyst wall is usually T2 dark (due to haemosiderin) + signal voids on SWI ± an adherent nonenhancing T2 dark mural nodule. NB: an enhancing mural nodule would be suspicious for malignant transformation to clear cell or endometrioid carcinoma.

• 2.

  Solid—spiculate fibrotic mass or plaque tethered to or invading adjacent structures. Usually T1 and T2 hypointense on MRI ± tiny hyperintense foci on T1 (blood products) or T2 (endometrial glands). Enhances post contrast. Associated adhesions may cause obstruction of fallopian tubes, ureters or bowel.

Typical locations for endometriotic deposits include:

• 1.

  Ovaries—usually cystic, often multiple and bilateral.

• 2.

  Pelvic peritoneum—usually solid.

  • (a)

    Pouch of Douglas—often obliterates the pouch and may extend inferiorly into rectovaginal septum ± invasion of posterior vaginal fornix or rectum. Often draws the ovaries together (‘kissing ovaries’ sign).

  • (b)

    Surface of rectosigmoid colon—may invade the wall and mimic a colonic tumour on CT. On MRI, an intact T2 hyperintense submucosal layer is usually seen overlying the mural deposit, giving a ‘mushroom cap’ appearance.

  • (c)

    Fallopian tubes—causes hydro- or haematosalpinx.

  • (d)

    Surface of bladder dome in uterovesical pouch—may invade wall and project into lumen.

  • (e)

    Parametrium—may obstruct distal ureters.

  • (f)

    Round ligament—R>L, may extend into the groin/labia via the canal of Nuck.

• 3.

  Abdominal wall—typically at a caesarean-section scar, usually solid. Due to implantation of endometrial tissue during surgery, so usually occurs without evidence of endometriosis in the pelvis. Can mimic a desmoid tumour.

Less common sites include:

• 1.

  Extrapelvic peritoneum—e.g. on the serosal surface of bowel (appendix > caecum > terminal ileum > other loops). May cause strictures, mimicking Crohn's disease or malignancy. Appendiceal involvement may cause appendicitis or mucocoele formation. Peritoneal deposits may also rarely occur within hernias, in the subphrenic space (R>L), mesentery, omentum or on the surface of the stomach, gallbladder, liver or spleen.

• 2.

  Thorax—uncommon, nearly always occurs in the presence of chronic pelvic disease.

  • (a)

    Pleura—nearly always right-sided. Causes cyclical haemopneumothorax.

  • (b)

    Lung parenchyma—rare; causes cyclical haemoptysis and lung nodules.

  • (c)

    Tracheobronchial tree—rare; causes cyclical haemoptysis and endoluminal nodules.

  • (d)

    Pericardium—rare; causes cyclical pericardial effusions.

• 3.

  Cervix—post surgery (e.g. cone biopsy). Rare.

• 4.

  Perineum—at an episiotomy scar. Rare.

• 5.

  Umbilicus—rare; may be primary or secondary (e.g. laparoscopy port site).

• 6.

  Pelvic nerves—sacral plexus, pudendal or sciatic nerves. Can cause cyclical sciatica. Very rare.

• 7.

  Within solid abdominal viscera—e.g. liver, pancreas, kidneys, adrenals. Very rare; usually cystic.

• 8.

  Other rare sites—e.g. breast, skin, muscle, bone, lymph nodes, nasal cavity, eyes, brain, spinal canal.

Erdheim-chester disease

Rare non-Langerhans cell histiocytosis with multisystem manifestations which are often characteristic on imaging. Usually presents in middle age.

• 1.

  Bones—involved in nearly all patients. Characteristically causes bilateral symmetrical metadiaphyseal sclerosis in the medulla of long bones, especially femora and tibiae. Other bones may also be involved, e.g. skull and facial bones.

• 2.

  Retroperitoneum—soft-tissue cuffing of the aorta (‘coated aorta’) and kidneys (‘hairy kidneys’) is almost pathognomonic if both are present. Tends to spare the IVC and ureters (cf. retroperitoneal fibrosis), though the renal pelvises and adrenals may be involved.

• 3.

  Orbits—bilateral retrobulbar inflammatory pseudotumours, usually intraconal.

• 4.

  CNS—variable manifestations: infiltration and enhancement of the pituitary and its stalk (causing diabetes insipidus), enhancing T2 hypointense dural masses or thickening, intracerebral lesions/masses or periarterial masses. Intracranial disease nearly always occurs in the presence of orbital or facial bone involvement.

• 5.

  Lungs—most commonly causes interlobular septal thickening, but other findings, e.g. GGO, centrilobular nodules, lung cysts, pleural thickening and effusions may be seen.

• 6.

  Cardiovascular—pericardial thickening and effusion ± infiltrative soft-tissue mass involving the myocardium (especially right atrium and AV groove). Soft-tissue cuffing of the thoracic aorta and its branches may be seen.

• 7.

  Other rare sites—skin, breasts, lymph nodes, thyroid, testes, other abdominal viscera.

Familial mediterranean fever

Inherited (AR) inflammatory serositis mainly affecting young adults of Mediterranean heritage. Most commonly presents with recurrent episodes of peritonitis ± skin rash. Imaging findings include:

• 1.

  Peritonitis—peritoneal thickening and ascites without another cause, ± mesenteric adenopathy and fat stranding ± hepatosplenomegaly.

• 2.

  Synovitis—joint effusion and soft-tissue swelling; may be mono- or polyarticular, lower > upper limbs. Usually nonerosive.

• 3.

  Pleuritis—pleural effusions.

• 4.

  Pericarditis—rare.

• 5.

  Complications of chronic disease—encapsulating peritonitis with cyst formation, peritoneal mesothelioma, systemic amyloidosis.

• 6.

  Possible associations—vasculitis, multiple sclerosis, haemolytic anaemia.

Gaucher disease

Commonest hereditary (AR) lysosomal storage disease, most common in Ashkenazi Jews. Results in the accumulation of glucosylceramide-filled macrophages (Gaucher cells) in the bone marrow, spleen and liver. May present in infants, children or young adults depending on subtype.

• 1.

  Bones—most commonly spine and long bones. Features include:

  • (a)

    Osteopenia, remodelling (Erlenmeyer flask), lytic lesions and pathological fractures.

  • (b)

    Bone infarcts and avascular necrosis with resultant sclerosis, H-shaped vertebrae and femoral/humeral head collapse.

  • (c)

    On MRI: diffuse T1 hypointense marrow replacement + bone infarcts.

  • (d)

    Increased risk of osteomyelitis.

• 2.

  Splenomegaly—typically massive ± focal infarcts. Focal masses are also common, comprising of Gaucher cells or extramedullary haematopoiesis.

• 3.

  Hepatomegaly—less marked than splenomegaly. Focal nodules may be seen.

• 4.

  Lungs—uncommon, typically in the presence of severe bone and visceral disease. Interlobular septal thickening, GGO, consolidation and bronchial wall thickening may be seen.

Generalized lymphatic anomaly

Also known as lymphangiomatosis. Rare congenital disease usually presenting in childhood, characterized by widespread lymphangiomas which can involve nearly any organ or tissue except the CNS. Most common sites include:

• 1.

  Bones—especially axial and proximal appendicular skeleton. Numerous well-defined cysts with thin sclerotic margins and preserved cortex.

• 2.

  Soft tissues—including skin, mediastinum, retroperitoneum, mesentery and neck.

• 3.

  Spleen—multiple lymphatic cysts.

• 4.

  Pleural and pericardial effusions and ascites—often chylous.

• 5.

  Lungs (diffuse pulmonary lymphangiomatosis)—thickening of interlobular septa and bronchovascular bundles ± GGO.

Related conditions include:

• 1.

  Cystic angiomatosis—less aggressive, usually presenting in adolescence or adulthood.

• 2.

  Kaposiform lymphangiomatosis—more aggressive, with more severe and infiltrative thoracic involvement and poorer prognosis. Also associated with thrombocytopenia, resulting in haemorrhagic effusions.

• 3.

  Gorham-Stout disease—also known as vanishing bone disease. Progressive osteolysis also involving cortex without a periosteal reaction. Usually limited to one bone, though the process can spread to adjacent bones and soft tissues. Splenic cysts may also be seen.

Gorlin-Goltz syndrome

Also known as basal cell naevus syndrome. Hereditary (AD) neurocutaneous syndrome characterized by:

• 1.

  Multiple cutaneous basal cell carcinomas at a young age—NB: patients are highly sensitive to ionizing radiation (especially radiotherapy), which can trigger the formation of skin tumours.

• 2.

  Multiple odontogenic keratocysts in the mandible and/or maxilla.

• 3.

  Dense calcification of the falx, tentorium and diaphragma sellae.

• 4.

  Rib anomalies (especially 3rd–5th)—bifid, fused, splayed or hypoplastic.

• 5.

  Palmoplantar pits or keratosis.

• 6.

  Increased risk of medulloblastoma, meningioma, ovarian/cardiac fibroma, fetal rhabdomyoma, mesenteric and pleural cysts.

• 7.

  Other skeletal anomalies—vertebral anomalies, pectus excavatum/carinatum, Sprengel deformity, poly/syndactyly, flame-shaped lucencies in hands and feet.

• 8.

  Other CNS anomalies—ventriculomegaly, cavum septum pellucidum, corpus callosum dysgenesis, colloid cyst.

• 9.

  Other clinical features—macrocephaly, hypertelorism, frontal bossing, cleft lip, high-arched palate, ocular anomalies, dermal cysts.

Graft-versus-host disease (GvHD)

Common and serious immunologic complication of allogeneic haematopoietic stem cell transplantation. May be acute (10–100 days post transplant) or chronic (>100 days)—each has different imaging features. NB: GvHD does not usually occur <10 days post transplant (unlike many infectious complications) since the transplanted marrow has not yet started functioning.

Haemochromatosis

• 1.

  Primary—AR disorder of iron metabolism. Results in iron deposition in the liver, pancreas, heart, pituitary, thyroid and synovium.

• 2.

  Secondary—two causes:

  • (a)

    Increased hepatic iron uptake—due to cirrhosis or chronic anaemias (e.g. thalassaemia, myelodysplasia). Iron deposition in liver ± pancreas and thyroid.

  • (b)

    Iron overload—due to multiple blood transfusions (e.g. for thalassaemia) or chronic iron supplementation (oral or IV). Iron deposition in spleen, bone marrow and liver.

• 3.

  Clinical—cirrhosis, skin pigmentation, diabetes, arthropathy and, later, ascites and cardiac failure.

• 4.

  Liver biopsy can aid assessment of patients without typical haemochromatosis-associated HFE genotypes who have serum ferritin concentrations >1000 µg/L, because many such patients have an inflammatory disease, not iron overload.

Haemolytic-uraemic syndrome

Multisystem thrombotic microangiopathy typically triggered by gut infection with Shiga toxin-producing E. coli . Most common in young children; presents initially with bloody diarrhoea and a triad of thrombocytopenia, haemolytic anaemia and AKI. Causes microvascular ischaemia of:

• 1.

  Kidneys—most common site. Increased cortical echogenicity on US with reduced blood flow in renal parenchyma and high resistance Doppler waveform in renal arteries. CT may show patchy infarcts, diffuse cortical necrosis or generalized poor renal enhancement.

• 2.

  GI tract—haemorrhagic or ischaemic colitis, or less commonly enteritis.

• 3.

  CNS—bilateral areas of increased DWI signal ± haemorrhage, especially in basal ganglia, thalami and deep white matter.

• 4.

  Others—necrotizing pancreatitis, hepatic infarcts, myocardial infarction, pulmonary haemorrhage. These features are more common in the atypical form of HUS, which is caused by an underlying genetic predisposition (complement system mutation) together with a trigger (e.g. infection, trauma, surgery, pregnancy, systemic diseases) and can occur in adults; this has a poorer prognosis.

Haemophagocytic lymphohistiocytosis

Immune disorder characterized by abnormal macrophage activation. May be primary (familial) or secondary to infection (especially viruses, e.g. EBV), malignancy (especially haematological), autoimmune disorders (e.g. juvenile idiopathic arthritis, SLE, vasculitis) or immune suppression. Most common in infants and young children. Imaging features include:

• 1.

  Lungs—consolidation, pulmonary oedema/haemorrhage, pleural effusions.

• 2.

  Abdomen—hepatosplenomegaly, periportal and gallbladder oedema, enlarged echogenic kidneys, ascites, adenopathy.

• 3.

  CNS—periventricular T2 hyperintensities, enlarged extraaxial fluid spaces and ventriculomegaly, meningeal enhancement and/or enhancing intraaxial lesions.

Henoch-Schönlein purpura

Multisystem small vessel IgA vasculitis. Typically presents in children with purpura (especially lower limbs). Usually self-limiting. Imaging features include:

• 1.

  GI tract—bowel wall oedema and haemorrhage, mural hypervascularity, ascites, mesenteric oedema and adenopathy. Intussusception (especially ileoileal) can occur. Bowel infarction is rare.

• 2.

  Joints—synovitis, joint effusions, soft-tissue swelling.

• 3.

  Urinary tract—nephritis (enlarged echogenic kidneys); urothelial thickening, strictures or haematomas; penoscrotal oedema, orchitis.

• 4.

  Lungs—pulmonary oedema/haemorrhage, pleural effusions. Rare.

• 5.

  CNS—cerebral oedema/haemorrhage, venous sinus thrombosis, PRES. Rare.

• 6.

  Other rare manifestations—acute pancreatitis, adrenal haemorrhage, myocardial infarction.

Hereditary haemorrhagic telangiectasia (HHT)

Inherited (AD) disorder characterized by multiple telangiectasias in the skin and mucous membranes and vascular malformations in many organs. Classically presents with recurrent epistaxis.

• 1.

  Lungs—AVMs are common and often symptomatic due to haemorrhage, right-to-left shunting and paradoxical emboli (resulting in stroke or cerebral abscesses). Most patients with >1 pulmonary AVM will have HHT.

• 2.

  Liver—commonly involved but often asymptomatic. Malformations may be arterioportal, arteriovenous or portovenous. Small malformations (telangiectasias) appear as <1 cm arterially enhancing lesions that equilibrate on the portal phase. Larger malformations appear as tortuous vascular connections or large (>1 cm) confluent vascular masses with persistent enhancement. Arterial enhancement of the liver is often diffusely heterogeneous, with dilated hepatic arteries and veins due to AV shunting + early venous filling ± high-output heart failure. FNH-like lesions may also be seen. Liver enhancement usually becomes homogeneous on the portal phase. Severe arterioportal shunting or NRH may lead to portal hypertension. Rarely, an ischaemic or necrotizing cholangiopathy may occur if severe AV shunting ‘steals’ oxygenated blood from the bile ducts.

• 3.

  GI tract—telangiectasias and/or AVMs may occur at any point along the GI tract causing recurrent bleeding, but only the larger malformations are visible on imaging.

• 4.

  CNS—intracranial or spinal AVMs (usually small and superficial), arteriovenous fistulas, capillary telangiectasias and developmental venous anomalies may be seen.

• 5.

  Other rare sites—pancreas, spleen.

Homocystinuria

AR inborn error of metabolism resulting in the accumulation of homocysteine.

• 1.

  Brain—multiple white matter lesions and infarcts at a young age. Can result in seizures and developmental delay.

• 2.

  Tall stature, slim build and arachnodactyly, resembling Marfan syndrome.

• 3.

  Pectus excavatum or carinatum, kyphoscoliosis, genu valgum and pes cavus.

• 4.

  Osteoporosis (not seen in Marfan syndrome).

• 5.

  Aortic root dilatation—due to cystic medial degeneration of elastic arteries.

• 6.

  Arterial and venous thromboses.

• 7.

  Lens subluxation—usually downward (cf. Marfan syndrome).

Hydatid disease

Parasitic infection caused by the larval stage of the Echinococcus tapeworm. Humans become accidental intermediate hosts after ingesting the eggs. The larvae penetrate through the bowel wall and primarily infect the liver, though any organ or tissue can be involved. There are two main types: