Prader-Willi syndrome is a rare genetic disorder. It is the most common cause of obesity caused by a genetic syndrome.
Prader-Willi syndrome is primarily characterized by:
sexual infancy: hypogonadism
morbid obesity resulting from hyperphagi...
Preaxial polydactyly refers to polydactyly where the additional digit is towards the first digit of the hand (radial side) or foot (medially).
Preaxial polydactyly is less common than post-axial polydactyly, with an estimated incidence of 1 in 7000.
Primary progressive aphasia was first described in 1982 and is the umbrella term for the language-variant frontotemporal dementias associated with frontotemporal lobar degeneration (FTLD) 3.
It is an insidious disorder characterized by gradual impairment of speech and lan...
Progeria is a term used for any syndrome in which a person is prematurely aged, however, it most commonly refers to Hutchinson-Gilford progeria syndrome (HGPS).
Although the primary clinical manifestations of progeria include short stature and skin changes, the disease is...
Progressive postnatal pansynostosis (PPP) is a rare form of craniosynostosis characterized by the late fusion of all cranial sutures.
This type of craniosynostosis occurs insidiously after birth and presents later in life unlike other types of craniosynostosis which occur during t...
Pronator teres syndrome (also called pronator syndrome) is one of three common median nerve entrapment syndromes; the other two being anterior interosseous nerve syndrome and the far more common carpal tunnel syndrome. Signs and symptoms result from compression of the median nerve in the upper f...
Proteus syndrome is a rare congenital, multisystemic, hamartomatous condition characterized by asymmetrical overgrowth of almost any part of the body and a broad spectrum of manifestations. It can affect tissue from any germinal layer. It is suspected to be a genetic condition, but a particular ...
Pseudoxanthoma elasticum (PXE), also known as Grönblad–Strandberg syndrome, is a systemic condition characterized by the degeneration of elastic fibers. It has multiorgan manifestations.
Its prevalence is estimated to be around 1 in 25,000 9.
Patients may ...
PTEN (phosphatase and tensin homolog) gene mutation is associated with a few conditions known as PTEN-related diseases, with relatively similar clinical and radiological manifestations. They include:
Those not f...
Pulled elbow (also known as nursemaid's elbow) is a subluxation of the radial head into the annular ligament, which usually spontaneously or easily reduces and rarely demonstrates abnormal radiographic features. It should be distinguished from dislocation of the radial head.
Quadrangular space syndrome also known as quadrilateral space syndrome is an uncommon diagnosis mainly because of lack of literature on the subject and possible misdiagnosis.
Quadrangular space syndrome is present on ~1% of shoulder MRIs 6.
Quadriceps (anterior suprapatellar) fat pad impingement syndrome is a rare cause of anterior knee pain although quadriceps fat pad edema may often, and possibly more commonly, be incidental 1,2.
The quadriceps fat pad is enlarged with mass effect on the adjacent su...
Radial tunnel syndrome is an entity that refers to entrapment (tunnel syndrome) of the radial nerve in the forearm, as it occurs in the supinator syndrome. Some authors believe this is an early form of the posterior interosseous nerve syndrome 5.
The syndrome is character...
Radiologically isolated syndrome (RIS) is defined by MRI findings meeting the McDonald criteria for multiple sclerosis in the brain and/or spinal cord in asymptomatic patients. Radiological progression usually occurs in approximately 66% of patients with RIS, while ~33% per 5-year-period will su...
Raghib syndrome is a rare developmental complex. It consists of:
persistence of the left superior vena cava
coronary sinus ostial atresia
atrial septal defect
It has also been associated with other congenital malformations including ventricular septal defects, enlargement of the tricuspid an...
Raine syndrome, also known as lethal osteosclerotic bone dysplasia, is a very rare genetic disorder. Infants with this syndrome present with numerous characteristic craniofacial features as well as cerebral calcifications. Many individuals with this disorder are stillborn or die as neonates 4.
Ramsay Hunt syndrome (RMS), also known as herpes zoster oticus, is shingles of the facial nerve. It is due to reactivation of the varicella zoster virus in the geniculate ganglion.
Ramsay Hunt syndrome classically presents with a triad of 3,4:
facial nerve pal...
RAPADILINO syndrome is a rare autosomal-recessive syndrome that results from mutations in the RECQL4 gene 1.
RAPADILINO syndrome is a rare condition, prevalence is unknown. It is, however, more common and was first described in Finnish populations 2.
The acronym RAPADI...
Raymond syndrome is a posterior circulatory stroke syndrome due to a lesion in the ventral medial mid-pons. It is an extremely rare condition, with only a handful of cases described in the literature.
Clinically, 2 subtypes have been reported 1:
Raynaud phenomenon (also known as Raynaud syndrome) describes a localized vasculopathy whereby there is an exaggerated vascular response to cold temperature or emotional stresses.
Raynaud phenomenon is classified as being either 'primary' or idiopathic, or 'secondary' to another un...
Reactive arthritis (ReA) is a sterile inflammatory monoarticular or oligoarticular arthritis that follows an infection at a different site, commonly enteric or urogenital. It is classified as a type of seronegative spondyloarthropathy.
Reactive arthritis was formerly known as Reite...
Reversible acute cerebellar toxicity (REACT) syndrome is a potentially reversible acute encephalopathic syndrome 1,2.
REACT is a rare syndrome that has been associated with several opioid and chemotherapeutic agents, including Minnelide 1,2.
Renal cysts and diabetes syndrome (RCAD), also known as maturity-onset diabetes of the young, type 5 (MODY5), refers to the combination of renal cortical cysts and diabetes mellitus in patients with mutations in the HNF1B gene. When renal cysts are associated with these mutations without disturb...
Rett syndrome is a rare neurodegenerative disease seen in young girls in the 2nd to 4th months of life. The majority of cases result from a mutation in the MECP2 gene; a more severe subset of the disease arises from a CDKL5 mutation1.
Following a period of normal developm...
Rhupus syndrome is a term traditionally used to describe patients uncommonly having the coexistence of
systemic lupus erythematosus (SLE) and
rheumatoid arthritis (RA)
The Rieger anomaly refers to the maldevelopment of the anterior chamber of the ocular globe. The iris and cornea do not form correctly, findings including:
hypoplastic iris stroma
corectopia: an off-center pupil in the iris
colobomas of the iris (pseudopolycoria)
Patients are at increased ri...
Right middle lobe syndrome refers to chronic right middle lobe collapse, without an obstructing lesion. It is usually with associated bronchiectasis.
Right middle lobe syndrome is usually encountered in older adults, with a predilection for women (see Lady Windermere syndrome). I...
Riley-Day syndrome or familial dysautonomia is a rare neurodevelopmental genetic autosomal recessive disorder that primarily affects the autonomic nervous system 1,9.
Familial dysautonomia saw in Ashkenazi Jews of Eastern European Jewish ancestry 1.
Ritscher-Schinzel syndrome (RTSC), also known as 3C (cranio-cerebello-cardiac) syndrome, is a rare entity with a variable spectrum of CNS (primarily cerebellar), craniofacial, and congenital heart defects.
Roberts syndrome, also known as Roberts-SC phocomelia syndrome, pseudothalidomide syndrome, or Appelt-Gerken-Lenz syndrome, is a rare congenital malformation syndrome.
intrauterine growth restriction
postnatal growth retardation
failure to thrive
Robinow-Sorauf syndrome (RSS) is a rare, autosomal dominant type of acrocephalosyndactyly syndrome (ACS).
Rather than being a distinct ACS, it has now generally accepted that RSS is, in fact, part of the Saethre-Chotzen syndrome phenotypic spectrum 1. This is due to similar phenotype and both b...
Robinow syndrome is a rare heterogeneous genetic disorder with at least two distinct forms.
The syndrome can affect several systems, including:
mesomelic limb shortening: mesomelia
characteristic facies anomalies
Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy or Rosai-Dorfman-Destombes disease, is a rare benign idiopathic proliferative disease that involves phagocytic histiocytes.
The disease predominantly occurs in young adults with a mean age at pre...
Rotational vertebral artery occlusion syndrome, also known as bow hunter's syndrome, is a rare form of vertebrobasilar insufficiency secondary to dynamic compression of the usually-dominant vertebral artery.
It has many predisposing etiologies, but is most often due to large osteoph...
Rothmund-Thomson syndrome (RTS) is an extremely rare autosomal recessive disorder with heterogeneous clinical features.
It is characterized by many features which include:
poikiloderma: characteristic rash, typically develops in infancy
sparse hair, eyelashes, and/or ey...
Rubinstein-Taybi syndrome (RTS) is a very rare genetic multi-system disorder primarily characterized by intellectual disability, broad and often angulated thumbs and halluces, and distinctive facial features.
The estimated incidence is 1 in 100,000-125,000 live births 5.
Russell-Silver dwarfism is a very rare syndrome representing a form of primordial dwarfism.
single umbilical artery
intrauterine growth restriction: tends to give an asymmetrical IUGR
postnatal growth restriction
relatively large calvarium: ...
Ruvalcaba syndrome (also known as Ruvalcaba-Myhre-Smith syndrome) is one of a group of disorders related to the congenital skeletal disturbance. It is characterized by:
intellectual (not invariably) and physical disability
SADDAN syndrome is an acronym for severe achondroplasia with developmental delay and acanthosis nigricans. It is an extremely rare condition, and as the name states, comprises a combination of skeletal, brain and cutaneous anomalies.
The syndrome results from a mutation in ...
Saethre-Chotzen syndrome (also known as type III acrocephalosyndactyly) is characterized by limb and skull abnormalities.
It is the most common craniosynostosis syndrome and affects 1:25 - 50,000 individuals.
Males and females are equally affected.
The Sakati-Nyhan syndrome, also known as Sakati-Nyhan-Tisdale syndrome or acrocephalosyndactly type III, is an extremely rare type of acrocephalopolysyndactyly.
Its main features include:
congenital limb abnormalities
congenital heart defects
History and etymology
Sampson syndrome refers to a type of superficial endometriosis, where multiple superficial plaques may be seen scattered in the peritoneum and pelvic ligaments.
The patient may present with non-specific abdominal pain.
At laparoscopy, they are typi...
The SAPHO syndrome is an acronym that refers to a rare syndrome that is manifested by a combined occurrence of 2:
It classically tends to present in young to middle-aged adults. Presentation in the pediatric popu...
Schimmelpenning syndrome is a rare and variable congenital multisystem condition characterized by extensive linear sebaceous nevi and multisystem neuroectodermal abnormalities. It is an epidermal nevus syndrome (ENS).
Classical triad including sebaceous nevi, seizures, an...
Schindler disease is a rare lysosomal storage disorder characterized by deficiency of alpha-N-acetylgalactosaminidase (alpha-NAGA or alpha-galactosidase B).
It is a rare disease with autosomal recessive inheritance.
Age and severity of presentation depends ...
Sclerosteosis is a rare autosomal recessive bone dysplasia resulting in sclerosis and hyperostosis, particularly of the skull, mandible and tubular bones. It is closely related to Van Buchem disease 1.
Sclerosteosis is a very rare disease, with only around 100 cases reported. Ther...
The seatbelt syndrome is the constellation of traumatic thoracic, abdominal and/or vertebral column injuries associated with three-point seatbelts 1,2:
lumbar spine fracture
female breast trauma
Seckel syndrome is an autosomal recessive congenital dwarfing disorder.
The estimated incidence is ~1:10,000. There is no recognized gender predilection.
It is clinically characterized by many features including:
intrauterine growth restriction
Segmental arterial mediolysis (SAM) is an increasingly recognized vascular disease of the middle-aged and elderly and a leading cause of spontanoeus intra-abdominal hemorrhage. It is characterized by fusiform aneurysms, stenoses, dissections and occlusions within splanchnic arterial branches. Im...
Sepsis is a syndrome, with a poorly understood pathogenesis, characterized clinically by a recognized set of signs and symptoms in someone with presumed infection.
Sepsis was defined by The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) in 2016 as ...
Septic-embolic encephalitis, also known as septic-embolic brain abscess, refers to a focal or diffuse brain infection, ischemic and hemorrhagic damages following infective thromboembolism from any part of the body. It is usually caused by bacterial infections from endocarditis.
Serrated polyposis syndrome (SPS), also called hyperplastic polyposis syndrome, is one of numerous polyposis syndromes and is characterized by the presence of multiple serrated polyps or a mixture of serrated and hyperplastic polyps, with the exact number required for diagnosis dependent on loca...
The severe acute respiratory syndrome (SARS) is a zoonotic illness caused by severe acute respiratory syndrome-related coronavirus (SARS-CoV-1), a coronavirus. The disease was first seen in the city of Foshan in Guangdong Province in China in 2002 and was traced back to the Himalayan (masked) p...
Sézary syndrome (SS) is a type of primary cutaneous T-cell lymphoma.
It is clinically characterized by an extensive erythematous rash covering most of the body as well as the presence of malignant lymphocytes in the blood.
History and etymology
It is named after Albert...
Shapiro syndrome is a very rare condition characterized by the triad of episodic hypothermia, hyperhidrosis, and agenesis of the corpus callosum 1. A similar syndrome, characterized by episodic hyperthermia and agenesis of the corpus callosum, has been termed reverse Shapiro syndrome 2.
Sheehan syndrome is a rare cause of pituitary apoplexy and hypopituitarism. It only occurs in postpartum females who experience large volume hemorrhage and hypovolemic shock, either during delivery or afterward with resultant necrosis of anterior pituitary cells 4.
Advances in obs...
Shone syndrome, also known as Shone complex, is a rare syndrome characterized by left-sided, obstructive congenital heart defects.
Shone syndrome is thought to be very rare, accounting for less than 1% of all congenital heart disease 1.
Patients, usually ne...
Short lasting unilateral neuralgiform headache attacks can present with either conjunctival injection and tearing (SUNCT) or with cranial autonomic symptoms (SUNA) are rare headache syndromes that belong to a larger group of headaches known as trigeminal autonomic cephalgia and can present very ...
Short rib polydactyly syndrome(s) (SRPS) comprise a rare group of severe osteochondrodysplasias. There are four major recognized types present:
type I: Saldino-Noonan type
type II:: Majewski type
type III: Verma-Naumoff type
type IV: Beemer-Langer type
There may also be other very rare type...
SHORT syndrome refers to an acronym which primarily comprises of the following features:
S: short stature
H: hyperextensibility of joints and/or inguinal hernia
O: ocular depression
R: Rieger anomaly
T: teething delay
In addition to these there can be numerous associated minor features whi...
Shrinking lung syndrome refers to a rare thoracic complication of systemic lupus erythematosus (SLE) characterized by:
restrictive pattern on pulmonary function tests
As with SLE in general, it is thought to carry a increased female pr...
Shwachman-Diamond syndrome (SDS) or Shwachman-Bodian-Diamond syndrome (SBDS) is a rare autosomal recessive disorder characterized by 1 :
exocrine pancreatic insufficiency
bone marrow hypoplasia (cyclic neutropenia)
Shwachman-Diamond syndrome is a ra...
The Shy-Drager syndrome is a neurodegenerative disease, and one of the manifestations of multiple systemic atrophy (MSA).
It is important to note that the current belief that olivopontocerebellar degeneration, Shy-Drager syndrome and striatonigral degeneration are different manifes...
Acute chest syndrome (ACS) in sickle cell disease is a leading thoracic complication - as well as leading cause of mortality - in those affected by sickle cell disease. The diagnosis is made on the combination of new pulmonary opacity on chest x-ray with at least one new clinical symptom or sign...
The silent sinus syndrome represents maxillary sinus atelectasis that results in painless enophthalmos, hypoglobus and facial asymmetry 1-3. Some authors restrict the term to patients with no history of sinusitis, trauma or surgery 2. Some authors suggest that is part of the spectrum of chronic ...
Simpson-Golabi-Behmel syndrome is a rare X-linked recessive disorder of pre- and postnatal overgrowth syndrome represented by mild to severe intellectual disability 3,7, anomalies of the musculoskeletal system, cardiovascular system, central nervous system, renal and gastrointestinal tract were ...
Sinus tarsi syndrome (STS) is the clinical syndrome of pain and tenderness of the lateral side of the hindfoot, between the ankle and the heel. Imaging often demonstrates the ligaments and soft tissues in the sinus tarsi are injured.
Sinus tarsi syndrome has been described in danc...
Sjögren-Larsson syndrome is a rare inherited autosomal recessive neurocutaneous syndrome and leukodystrophy characterized by the clinical triad of ichthyosis, intellectual disability, and spastic diplegia or tetraplegia.
Although considered very rare, the exact prevalence is not k...
Sjögren syndrome, or Sjögren disease, is an autoimmune condition of the exocrine glands that produce tears and saliva.
Sjögren syndrome is the second most common autoimmune disorder after rheumatoid arthritis. There is a recognized female predilection with F:M ratio of ≈9:1. Pati...
Slit ventricle syndrome refers to cerebrospinal fluid shunt-related symptoms in the setting of small ventricles demonstrated on radiologic studies.
The presence of characteristic symptoms is required to diagnose slit-ventricle syndrome and must be distinguished from slit-...
Small for size syndrome (SFSS) is a clinical syndrome caused by the transplantation of a liver graft that is too small for a recipient. It occurs when the graft‐to‐recipient weight ratio (GRWR ) is less than 0.8% or a graft volume to standard liver volume ratio (GV/SLV) is less than 35%.
SMART syndrome, an acronym for stroke-like migraine attacks after radiation therapy, is an uncommon delayed complication of cerebral radiation therapy.
Patients usually present years after radiation therapy (6-30 years in a case series) with seizures and subacute stroke-l...
Smith-Lemli-Opitz syndrome (SLOS) also known as 7-dehydrocholesterol reductase deficiency, is an inborn error of cholesterol synthesis.
The estimated incidence is at 1:20,000-40,000 live births. Prevalence may be greater in Nordic countries.
Smith-Magenis Syndrome (SMS) is a rare genetic syndrome which results from an interstitial deletion in chromosome 17p11.2.
The condition is known by several other names which are all similar variants related to its underlying karyotype: 17p deletion syndrome, 17p11.2 monosomy, chro...
Snapping hip syndrome (also known as coxa saltans or dancer’s hip) refers to a situation where there is an audible snapping sound produced during motion of the hip.
Some reports suggest that up to 10% of population may have this to some degree 8.
This condition is cla...
Sneddon syndrome is a type of systemic non-inflammatory vasculopathy characterized by livedo reticularis and progressive and occlusive cerebrovascular thrombosis involving the medium-sized arteries.
livedo reticularis as a skin manifestation
progressive cerebral stroke...
Solitary rectal ulcer syndrome (SRUS) is a chronic, benign disorder characterized by the presence of an abnormality of the rectum in persons who have a long history of straining during defecation. It is a misnomer because only a third of patients have a solitary ulcer, and many have no ulcers at...
Sotos syndrome it is an autosomal dominant syndrome considered as a form of cerebral gigantism, most characterized by the prenatal and postnatal overgrowth.
There is no ethnic group predominance and has been detected throughout the world. The prevalence is not known but is estimat...
Spigelian-cryptorchidism syndrome ( also known as Raveenthiran syndrome ) is the association of Spigelian hernias and cryptorchidism in children.
It is reported that ~50% (range 28-75%) range of pediatric patients with Spigelian hernias will have ipsilateral cryptorchidism 1,2.
Spinal cord injury (SCI) can be traumatic or non-traumatic (i.e. neoplastic/stenosis) but the syndromes associated with spinal cord injury can be seen in all etiologies.
Injury to the spinal cord can be incomplete or complete and depends upon the mechanism of injury. This is important as differ...
Spondylocostal dysostosis (SCDO) is a rare condition characterized by short-trunk dwarfism secondary to developmental anomalies of the vertebrae and ribs. Previously the condition Jarcho-Levin syndrome (also known as spondylothoracic dysostosis) was grouped together with spondylocostal dysostosi...
Spondyloepiphyseal dysplasia is a form of skeletal dysplasia mainly involving the spine and proximal epiphyses.
short trunk with protruding abdomen
craniovertebral junction stenosis
Stauffer syndrome is paraneoplastic nephrogenic hepatomegaly. It most commonly occurs in the setting of renal cell carcinoma, and is the enlargement of the liver without hepatic metastases. It is a cause of cholestasis and cholestatic jaundice.
History and etymology
It is named after Maurice ...
Stevens-Johnson syndrome (SJS) is an acute inflammatory skin condition.
SJS is on a spectrum of disease with toxic epidermal necrolysis syndrome (TENS) at the more severe end. Terminology depends on how much of the body surface area is involved 1,2:
SJS-TENS overlap: 1...
Stewart-Treves syndrome refers to an angiosarcoma seen in the setting of lymphedema 1.
It was classically attributed to lymphedemas induced by radical mastectomy to treat breast cancer. Nowadays, we know that it can arise in chronically lymphedematous regions of any cause 2.
The incidence is ...
Stickler syndrome refers to a group of disorders primarily affecting connective tissue.
Several gene mutations have been identified dependent on specific subtypes which include:
Stickler syndrome type I: COL2A1
Stickler syndrome type II: COL9A1
Stickler syndrome type III: COL11A1
Stiff person syndrome, previously known as stiff man syndrome, is a very rare neuromuscular disease.
Onset is usually between 30 and 50 years of age. An association with autoimmune disease and various malignancies is described and these are thought to play a role in the pathophysi...
Straight back syndrome refers to decreased thoracic kyphosis ("flattening") and decreased anteroposterior thoracic diameter, such that there is compression of cardiovascular or bronchial structures.
It should not be confused with flat back syndrome, which refers to decreased lumbar lordosis, o...
Sturge-Weber syndrome, or encephalotrigeminal angiomatosis, is a phakomatosis characterized by facial port wine stains and pial angiomas.
It is part of a wide spectrum of possible phenotypes included in the craniofacial arteriovenous metameric syndrome (CAMS).
Subacute encephalopathy with seizures in alcoholics (SESA syndrome) is a rare complication of chronic excessive alcohol consumption that can present with seizures and a variety of neurological deficits.
SESA syndrome is rare and seen in alcoholics who are not undergoing withdrawa...
Subclavian steal syndrome and subclavian steal phenomenon both result from severe proximal subclavian artery stenosis or occlusion resulting in retrograde flow in the ipsilateral vertebral artery.
Subclavian steal phenomenon refers to steno-occlusive disease of the proximal subclav...
Subependymal hamartomas are seen in patients with tuberous sclerosis. They are located along the ventricles and are mostly asymptomatic. As with other hamartomas, they grow at the same rate as the surrounding tissues.
On imaging, they appear as small intraventricular masses, smaller than 1 cm, ...
Sulcal artery syndrome is a rare cause of spinal cord infarction involving the territory of one of the sulcal arteries, which are penetrating branches of the anterior spinal artery, each vessel supplying either left or right side of the cord, but not both. The result is an incomplete Brown-Séqua...