Diseases

Hydrocephalus

Hydrocephalus (from Greek hydro-, meaning "water", and kephalos, meaning "head") is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid (CSF) in the brain. This causes increased intracranial pressure inside the skull and may cause progressive enlargement of the head if it occurs in childhood, potentially causing convulsion, tunnel vision, and mental disability. It was once informally called "Water on the brain."

Two types of hydrocephalus are commonly described non-communicating hydrocephalus and communicating hydrocephalus, although there is evidence that communicating forms can lead to obstruction of CSF flow in many instances.

In non-communicating hydrocephalus, the CSF in the ventricles can not reach the subarachnoid space. This results from obstruction of interventricular foramina, cerebral aqueduct, or the outflow foramens of the fourth ventricle (median and lateral apertures). The most common obstruction is in the cerebral aqueduct. A block at any of these sites leads rapidly to dilatation of one or more ventricles. If the skull is still pliable, as it is in children younger than 2 years, the head may enlarge.

In communicating hydrocephalus, the obstruction of CSF flow is in the subarachnoid space from prior bleeding or meningitis. This causes thickening of the arachnoid leading to blockage of the return-flow channels. In some patients, the spaces filled by CSF are uniformly enlarged without an increase in intercranial pressure. This special form of communicating hydrocephalus is called normal pressure hydrocephalus (NPH), which results specifically from impaired CSF reabsorption at the arachnoid granulations. NPH's clinical manifestations are gait abnormality, dementia, and involuntary urination. NPH usually occurs in elderly patients.

Hydrocephalus obesity hypogonadism

A very rare syndrome characterized mainly by obesity, buildup of fluid inside the skull (hydrocephalus) and impaired sex hormone production.

Hydrocephalus skeletal anomalies

A very rare syndrome characterized mainly by retarded growth, buildup of fluid (cerebrospinal fluid) inside the skull and various skeletal anomalies.

Hydrocephaly tall stature joint laxity

A very rare syndrome characterized mainly by a buildup of fluid inside the skull, abnormal brain development (corpus callosum) and a diaphragmatic hernia.

Hydrolethalus syndrome

A rare genetic disorder characterized by hydrocephalus, micrognathia and polydactyly.

Hydrops ectrodactyly syndactyly

More detailed information about the symptoms, causes, and treatments of Hydrops ectrodactyly syndactyly is available belo

Hydrops fetalis

Abnormal accumulation of fluid in the fetus which can be fatal. Excessive fluid leaves the blood and enters the tissues. It can have non-immune and immune (mother's immune system destroys fetal red blood cells).

Hydroxykynureninuria

A rare genetic disorder where a deficiency of the enzyme kynureninase (a vitamin B6) causes physical and mental problems. The deficiency can also occur in an acquired form which tends to be less severe

Hygroma cervical

An abnormal sac-like structure filled with lymph fluid that occurs in the neck area. It results from abnormal lymphatic structure development. The abnormality is present at birth and may vary in size from barely noticeable to large enough to affect breathing. Surgical removal can result in recurrence of all of the tissue is not removed. In some cases, the hygroma is too intertwined with other structures and surgery is not possible

Hymenolepiasis

A rare parasitic disease caused by a tapeworm called Hymenolepis nana or Hymenlepis dimunita. Infestation occurs through fecal contamination or by accidentally consuming insects that have eaten the parasitic eggs.

Hyper IgM syndrome

A rare inherited immunodeficiency disorder which causes frequent infections involving the ears, eyes, sinuses, lungs, skin, respiratory tract and other areas of the body. This condition is inherited in an X-linked recessive pattern.

X-linked hyper IgM syndrome is a condition that affects the immune system and occurs almost exclusively in males. People with this disorder have abnormal levels of proteins called antibodies or immunoglobulins. Antibodies help protect the body against infection by attaching to specific foreign particles and germs, marking them for destruction. There are several classes of antibodies, and each one has a different function in the immune system. Although the name of this condition implies that affected individuals always have high levels of immunoglobulin M (IgM), some people have normal levels of this antibody. People with X-linked hyper IgM syndrome have low levels of three other classes of antibodies: immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin E (IgE). The lack of certain antibody classes makes it difficult for people with this disorder to fight off infections.

Hyper-IgD syndrome

Hyper IgD syndrome (HIDS) is an inflammatory genetic where high levels of the immunoglobulin D cause disorder characterized by periodic episodes of fever associated with additional symptoms including joint pain, skin rash and abdominal pain. Most episodes last several days and occur periodically throughout life. The frequency of episodes and their severity vary greatly from case to case. It is originally described in 1984 by the Prof. Jos van der Meer at Leiden University Medical Centre.

Hyper-IgE Syndrome

Hyper-IgE syndrome (HIES, also called Job-Buckley syndrome, Job's syndrome and Buckley syndrome), is a heterogeneous group of disorders characterized by recurrent staphylococcal infections, unusual eczema-like skin rashes, severe lung infections that result in pneumatoceles (balloon-like lesions that may be filled with air or pus or scar tissue) and very high concentrations of the serum antibody IgE.

Hyper-reninism

An autonomous, excessive renin-producing tumor results secondary hyperaldosteronism with the subsequent hypertension

Hyperacusis

Hyperacusis is a health condition characterized by an over-sensitivity to certain frequency ranges of sound (a collapsed tolerance to normal environmental sound). A person with severe hyperacusis has difficulty tolerating everyday sounds, some of which may seem unpleasantly loud to that person but not to others.

Hyperadrenalism

Hyperadrenalism (medical condition): Excessive levels of adrenal hormones in the body. Symptoms depend on which hormone is involved and the degree of involvement. Adrenal hormones are aldosterone, corticosteroids, androgenic steroids, epinephrine and norepinephrine.

Hyperaldosteronism

A condition characterised by the excessive production and release into the circulation of aldosterone

Hyperaldosteronism familial type 2

Type 2 familial hyperaldosteronism, inherited as an autosomal dominant trait, causes hypertension secondary to primary aldosteronism that is not suppressed with dexamethasone. Patients present with an adrenal adenoma that secretes aldosterone. The observation of several families affected suggests that the molecular mechanism may be different than in type I familial hyperaldosteronism, but remains to be identified. Diagnostic suspicion should lead to the screening of patients by determining the aldosterone/renin ratio.

Hyperaldosteronism- familial type 1

Type I familial aldosteronism also called dexamethasone suppressible aldosteronism is a rare disorder inherited as an autosomal dominant trait. It is due to the ectopic expression of the aldosterone synthase in the fascicular zone of the adrenal gland. It is marked with early severe hypertension (often occurring before the age of 20), biological signs of primary aldosteronism of variable intensity, and an abnormal elevated level of 18-oxo- and 18-hydroxycortisol. The molecular defect is a recombination on the long arm of chromosome 8 leading a duplication-fusion between the 5' end of the gene coding for the 11 beta-hydroxylase (CYP11B1) and the 3' end of the gene coding for the aldosterone synthase (CYP11B2), two very similar (93%) and very closely located genes. All the modifications are located before the exon 5 of CYP11B2 which encodes amino acids allowing the aldosterone synthase function. The hybrid gene has the promoting part of CYP11B1, ACTH-sensitive, and the coding part of CYP11B2. This leads an excessive mineralocorticoids synthesis in the adrenal glands, governed by the hypothalamohypophyseal axis. Diagnosis and familial screening consist in providing evidence of the hybrid gene by Southern blot and/or PCR. Urinary tests show an important elevation of 18-oxo- and 18-hydroxycortisol. Once the diagnosis is ascertained, a specific treatment to slow the production of aldosterone is given; it combines small doses of dexamethasone and an anti-aldosterone