Polycythemia (also known as polycythaemia or polyglobulia) is a disease state in which the hematocrit (the volume percentage of red blood cells in the blood) is elevated.

It can be due to an increase in the number of red blood cells ("absolute polycythemia") or to a decrease in the volume of plasma ("relative polycythemia"). Polycythemia is sometimes called erythrocytosis, but the terms are not synonymous, because polycythemia refers to any increase in red blood cells, whereas erythrocytosis only refers to a documented increase of red cell mass.

The emergency treatment of polycythemia (e.g., in hyperviscosity or thrombosis) is by phlebotomy (removal of blood from the circulation). Depending on the underlying cause, phlebotomy may also be used on a regular basis to reduce the hematocrit. Cytostatics such as busulfan and hydroxyurea are sometimes used for long-term management of polycythemia.

Primary polycythemias are due to factors intrinsic to red cell precursors. Polycythemia vera (PCV), polycythemia rubra vera (PRV), or erythremia, occurs when excess red blood cells are produced as a result of an abnormality of the bone marrow. Often, excess white blood cells and platelets are also produced. PCV is classified as a myeloproliferative disease. Symptoms include headaches and vertigo, and signs on physical examination include an abnormally enlarged spleen and/or liver. In some cases, affected individuals may have associated conditions including high blood pressure or formation of blood clots. Transformation to acute leukemia is rare. Phlebotomy is the mainstay of treatment. A hallmark of polycythemia is an elevated hematocrit, with Hct > 55% seen in 83% of cases. A somatic (non-hereditary) mutation (V617F) in the "JAK2" gene is found in 95% of cases, though also present in other myeloproliferative disorders.

Primary familial polycythemia, also known as primary familial and congenital polycythemia (PFCP), exists as a benign hereditary condition, in contrast with the myeloproliferative changes associated with acquired PCV. In many families, PFCP is due to an autosomal dominant mutation in the "EPOR" erythropoietin receptor gene. PFCP can cause an increase of up to 50% in the oxygen-carrying capacity of the blood; skier Eero Mäntyranta had PFCP, which is considered to have given him a large advantage in endurance events.

The onset of HLH occurs under the age of 1 year in ~70% of cases. Familial HLH should be suspected if siblings are diagnosed with HLH or if symptoms recur when therapy has been stopped. Each full sibling of a child with familial HLH has a 25% chance of developing the disease, a 50% chance of carrying the defective gene (which is very rarely associated with any risk of disease) and a 25% chance of not being affected and not carrying the gene defect.

Patients with HLH, especially when untreated, may need intensive therapy. Therefore, HLH should be included in the differential diagnosis of ICU (Intensive Care Unit) patients with cytopenia and hyperferritinemia.

HLH clinically manifests with fever, enlargement of the liver and spleen, enlarged lymph nodes, yellow discoloration of the skin and eyes, and a rash.

Hemophagocytic lymphohistiocytosis (HLH), also known as haemophagocytic lymphohistiocytosis (British spelling), and hemophagocytic or haemophagocytic syndrome, is an uncommon hematologic disorder seen more often in children than in adults. It is a life-threatening disease of severe hyperinflammation caused by uncontrolled proliferation of activated lymphocytes and macrophages, characterised by proliferation of morphologically benign lymphocytes and macrophages that secrete high amounts of inflammatory cytokines. It is classified as one of the cytokine storm syndromes.

Myomatous erythrocytosis syndrome describes an excessive erythrocyte (red blood cells) production, occurring in about 0.5% of individuals affected by uterine leiomyomas (fibroids). This syndrome is believed to be caused by increased erythropoietin (EPO) production by the kidneys or by the leiomyomas themselves.

"Laboratory changes": massive accumulation of chylomicrons in the plasma and corresponding severe hypertriglyceridemia. Typically, the plasma in a fasting blood sample appears creamy (plasma lactescence).

"Clinical symptoms:" The disease often presents in infancy with colicky pain, failure to thrive, and other symptoms and signs of the chylomicronemia syndrome. In women the use of estrogens or first pregnancy are also well known trigger factors for initial manifestation of LPLD. At all ages, the most common clinical manifestation is recurrent abdominal pain and acute pancreatitis. The pain may be epigastric, with radiation to the back, or it may be diffuse, with the appearance of an emergent acute abdomen. Other typical symptoms are eruptive xanthomas (in about 50% of patients), lipemia retinalis and hepatosplenomegaly.

"Complications:" Patients with LPLD are at high risk of acute pancreatitis, which can be life-threatening, and can lead to chronic pancreatic insufficiency and diabetes.

Familial dysalbuminemic hyperthyroxinemia is a type of hyperthyroxinemia associated with mutations in the human serum albumin gene.

The term was introduced in 1982.

Apolipoprotein B deficiency (also known as "Familial defective apolipoprotein B-100") is an autosomal dominant disorder resulting from a missense mutation which reduces the affinity of apoB-100 for the low-density lipoprotein receptor (LDL Receptor) . This causes impairments in LDL catabolism, resulting in increased levels of low-density lipoprotein in the blood. The clinical manifestations are similar to diseases produced by mutations of the LDL receptor, such as familial hypercholesterolemia. Treatment may include, niacin or statin or ezetimibe.

It is also known as "normotriglyceridemic hypobetalipoproteinemia".

Familial dysbetalipoproteinemia or type III hyperlipoproteinemia (also known as remnant hyperlipidemia, "remnant hyperlipoproteinaemia", "broad beta disease" and "remnant removal disease") is a condition characterized by increased total cholesterol and triglyceride levels, and decreased HDL levels.

Signs of familial dysbetaproteinemia include xanthoma striatum palmare (orange or yellow discoloration of the palms) and tuberoeruptive xanthomas over the elbows and knees. The disease leads to premature atherosclerosis and therefore a possible early onset of coronary artery disease and peripheral vascular disease leading to a heart attack, i.e. myocardial infarction, chest pain on exercise, i.e. angina pectoris or stroke in young adults or middle aged patients.

Symptoms of the familial form include visual impairment caused by diffuse corneal opacities, target cell hemolytic anemia, and renal failure. Less common symptoms include atherosclerosis, hepatomegaly (enlarged liver), splenomegaly (enlarged spleen), and lymphadenopathy.

Fish-eye disease is less severe and most commonly presents with impaired vision due to corneal opacification. It rarely presents with other findings, although, atherosclerosis, hepatomegaly, splenomegaly, and lymphadenopathy can occur. Carlson and Philipson found that the disease was named so because the cornea of the eye was so opaque or cloudy with dots of cholesterol that it resembled a boiled fish.

If an individual only carry one copy of the mutated gene, they typically do not show symptoms.

Lipoprotein lipase deficiency (also known as "familial chylomicronemia syndrome", "chylomicronemia", "chylomicronemia syndrome" and "hyperlipoproteinemia type Ia") is a rare autosomal recessive lipid disorder caused by a mutation in the gene which codes lipoprotein lipase. As a result, afflicted individuals lack the ability to produce lipoprotein lipase enzymes necessary for effective breakdown of triglycerides.

HIDS is one of a number of periodic fever syndromes. It is characterised by attacks of fever, arthralgia, skin lesions including cyclical mouth ulcers, and diarrhea. Laboratory features include an acute phase response (elevated CRP and ESR) and markedly elevated IgD (and often IgA), although cases with normal IgD have been described.

It has mainly been described in the Netherlands and France, although the international registry includes a number of cases from other countries.

The differential diagnosis includes fever of unknown origin, familial Mediterranean fever (FMF) and familial Hibernian fever (or TNFα reception associated periodic syndrome/TRAPS).

Lecithin cholesterol acyltransferase deficiency (LCAT deficiency) is a disorder of lipoprotein metabolism. The disease has two forms: Familial LCAT deficiency, in which there is complete LCAT deficiency, and Fish-eye disease, in which there is a partial deficiency.

Lecithin cholesterol acyltransferase catalyzes the formation of cholesterol esters in lipoproteins.

Combined hyperlipidemia (or -aemia) (also known as multiple-type hyperlipoproteinemia) is a commonly occurring form of hypercholesterolemia (elevated cholesterol levels) characterised by increased LDL and triglyceride concentrations, often accompanied by decreased HDL. On lipoprotein electrophoresis (a test now rarely performed) it shows as a hyperlipoproteinemia type IIB. It is the most commonly inherited lipid disorder, occurring in around one in 200 persons. In fact, almost one in five individuals who develop coronary heart disease before the age of 60 have this disorder.

The elevated triglyceride levels (>5 mmol/l) are generally due to an increase in very low density lipoprotein (VLDL), a class of lipoproteins prone to cause atherosclerosis.

Hyperimmunoglobulinemia D with recurrent fever (HIDS) is a periodic fever syndrome originally described in 1984 by the internist Jos van der Meer, then at Leiden University Medical Centre. No more than 300 cases have been described worldwide.

The four men and two women were all diagnosed at middle age. The symptoms were slowly and steadily progressive. Telangiectasias developed over the face, trunk and arms. Increased serum erythropoietin levels, eventually exceeding 5000 mU /ml, preceded the intrapulmonary shunting and the development of hypoxemia. Sampling of the perinephric fluid revealed a clear, serous fluid with low levels of protein, few leukocytes and no cholesterol or triglycerides. An IgG monoclonal gammopathy was implicated in the four patients tested (with an associated kappa light chain in all three patients tested). Spontaneous venous thromboses occurred in three patients, two of whom also had spontaneous intracranial bleeding in the absence of blood vessels malformations.

Since then more patients with the syndrome have been reported.

TEMPI Syndrome is a novel orphan disease where the person share five characteristics from which the acronym is derived: telangiectasias, elevated erythropoietin and erythrocytosis, monoclonal gammopathy, perinephric fluid collection, and intrapulmonary shunting.

Hyperlipoproteinemia type II, by far the most common form, is further classified into types IIa and IIb, depending mainly on whether elevation in the triglyceride level occurs in addition to LDL cholesterol.

The two forms of this lipid disorder are:

- Familial combined hyperlipidemia (FCH) is the familial occurrence of this disorder, probably caused by decreased LDL receptor and increased ApoB.

- Acquired combined hyperlipidemia is extremely common in patients who suffer from other diseases from the metabolic syndrome ("syndrome X", incorporating diabetes mellitus type II, hypertension, central obesity and CH). Excessive free fatty acid production by various tissues leads to increased VLDL synthesis by the liver. Initially, most VLDL is converted into LDL until this mechanism is saturated, after which VLDL levels elevate.

Type I hyperlipoproteinemia exists in several forms:

- Lipoprotein lipase deficiency (type Ia), due to a deficiency of lipoprotein lipase (LPL) or altered apolipoprotein C2, resulting in elevated chylomicrons, the particles that transfer fatty acids from the digestive tract to the liver

- Familial apoprotein CII deficiency (type Ib), a condition caused by a lack of lipoprotein lipase activator.

- Chylomicronemia due to circulating inhibitor of lipoprotein lipase (type Ic)

Type I hyperlipoproteinemia usually presents in childhood with eruptive xanthomata and abdominal colic. Complications include retinal vein occlusion, acute pancreatitis, steatosis, and organomegaly, and lipemia retinalis.

Although hypercholesterolemia itself is asymptomatic, longstanding elevation of serum cholesterol can lead to atherosclerosis (hardening of arteries). Over a period of decades, elevated serum cholesterol contributes to formation of atheromatous plaques in the arteries. This can lead to progressive narrowing of the involved arteries. Alternatively smaller plaques may rupture and cause a clot to form and obstruct blood flow. A sudden blockage of a coronary artery may result in a heart attack. A blockage of an artery supplying the brain can cause a stroke. If the development of the stenosis or occlusion is gradual, blood supply to the tissues and organs slowly diminishes until organ function becomes impaired. At this point tissue ischemia (restriction in blood supply) may manifest as specific symptoms. For example, temporary ischemia of the brain (commonly referred to as a transient ischemic attack) may manifest as temporary loss of vision, dizziness and impairment of balance, difficulty speaking, weakness or numbness or tingling, usually on one side of the body. Insufficient blood supply to the heart may cause chest pain, and ischemia of the eye may manifest as transient visual loss in one eye. Insufficient blood supply to the legs may manifest as calf pain when walking, while in the intestines it may present as abdominal pain after eating a meal.

Some types of hypercholesterolemia lead to specific physical findings. For example, familial hypercholesterolemia (Type IIa hyperlipoproteinemia) may be associated with xanthelasma palpebrarum (yellowish patches underneath the skin around the eyelids), arcus senilis (white or gray discoloration of the peripheral cornea), and xanthomata (deposition of yellowish cholesterol-rich material) of the tendons, especially of the fingers. Type III hyperlipidemia may be associated with xanthomata of the palms, knees and elbows.

Familial hyperaldosteronism is a group of inherited conditions in which the adrenal glands, which are small glands located on top of each kidney, produce too much of the hormone aldosterone. Excess aldosterone causes the kidneys to retain more salt than normal, which in turn increases the body's fluid levels and causes high blood pressure. People with familial hyperaldosteronism may develop severe high blood pressure, often early in life. Without treatment, hypertension increases the risk of strokes, heart attacks, and kidney failure. There are other forms of hyperaldosteronism that are not inherited.

Familial hyperaldosteronism is categorized into three types, distinguished by their clinical features and genetic causes. In familial hyperaldosteronism type I, hypertension generally appears in childhood to early adulthood and can range from mild to severe. This type can be treated with steroid medications called glucocorticoids, so it is also known as glucocorticoid-remediable aldosteronism (GRA). In familial hyperaldosteronism type II, hypertension usually appears in early to middle adulthood and does not improve with glucocorticoid treatment. In most individuals with familial hyperaldosteronism type III, the adrenal glands are enlarged up to six times their normal size. These affected individuals have severe hypertension that starts in childhood. The hypertension is difficult to treat and often results in damage to organs such as the heart and kidneys. Rarely, individuals with type III have milder symptoms with treatable hypertension and no adrenal gland enlargement.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. The various types of familial hyperaldosteronism have different genetic causes.

It is unclear how common these diseases are. All together they appear to make up less than 1% of cases of hyperaldosteronism.

An affected infant typically has the following triad of signs and symptoms: soft-tissue swelling, bone lesions, and irritability. The swelling occurs suddenly, is deep, firm, and may be tender. Lesions are often asymmetric and may affect several parts of the body. Affected bones have included the mandible, tibia, ulna, clavicle, scapula, ribs, humerus, femur, fibula, skull, ilium, and metatarsals. When the mandible (lower jaw bone) is affected, infants may refuse to eat, leading to failure to thrive.

Thyroid dyshormonogenesis (or dyshormogenetic goiter) is a rare condition due to genetic defects in the synthesis of thyroid hormones.

Patients develop hypothyroidism with a goitre.either deficiency of thyroid enzymes or inability to concentrate or ineffective binding