Hepatosplenomegaly (commonly abbreviated HSM) is the simultaneous enlargement of both the liver (hepatomegaly) and the spleen (splenomegaly). Hepatosplenomegaly can occur as the result of acute viral hepatitis, infectious mononucleosis, and histoplasmosis or it can be the sign of a serious and life-threatening lysosomal storage disease. Systemic venous hypertension can also increase the risk for developing hepatosplenomegaly, which may be seen in those patients with right-sided heart failure.

Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an alloimmune condition that develops in a fetus, when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta. Among these antibodies are some which attack antigens on the red blood cells in the fetal circulation, breaking down and destroying the cells (hemolysis). The fetus can develop reticulocytosis and anemia. This fetal disease ranges from mild to very severe, and fetal death from heart failure (hydrops fetalis) can occur. When the disease is moderate or severe, many erythroblasts (immature red blood cells) are present in the fetal blood, and so these forms of the disease can be called "erythroblastosis fetalis" (or "erythroblastosis foetalis").

HDFN represents a breach of immune privilege for the fetus or some other form of impairment of the immune tolerance of pregnancy. Various types of HDFN are classified by which alloantigen provokes the response. In order of incidence, the types include ABO, anti-RhD, anti-RhE, anti-Rhc, anti-Rhe, anti-RhC, multiantigen combinations, and anti-Kell.

Signs of hemolytic disease of the newborn include a positive direct Coombs test (also called direct agglutination test), elevated cord bilirubin, and hemolytic anemia. It is possible for a newborn with this disease to have neutropenia and neonatal alloimmune thrombocytopenia as well.Hemolysis leads to elevated bilirubin levels. After delivery bilirubin is no longer cleared (via the placenta) from the neonate's blood and the symptoms of jaundice (yellowish skin and yellow discoloration of the whites of the eyes) increase within 24 hours after birth. Like other severe neonatal jaundice, there is the possibility of acute or chronic kernicterus, however the risk of kernicterus is higher because of the rapid destruction of blood cells. It is important to note that isoimmunization is a risk factor for neurotoxicity and lowers the level at which kernicterus can occur. Untreated profound anemia can cause high-output heart failure, with pallor, enlarged liver and/or spleen, generalized swelling, and respiratory distress.

HDN can be the cause of hydrops fetalis, an often-severe form of prenatal heart failure that causes fetal edema.

Many affected individuals have yellowing of the skin and eyes (jaundice) and an enlarged liver and spleen (hepatosplenomegaly). This condition also causes the body to absorb too much iron, which builds up and can damage tissues and organs. In particular, iron overload can lead to an abnormal heart rhythm (arrhythmia), congestive heart failure, diabetes, and chronic liver disease (cirrhosis). Rarely, people with CDA type I are born with skeletal abnormalities, most often involving the fingers and/or toes.

Congenital malaria is an extremely rare condition which occurs due to transplacental transmission of maternal infection.

Clinical features include fever, irritability, feeding problems, anemia, hepatosplenomegaly and jaundice. Clinical features commence only after 3 weeks due to the protective effect of transplacentally transmitted antibodies.

CDA type I is characterized by moderate to severe anemia. It is usually diagnosed in childhood or adolescence, although in some cases, the condition can be detected before birth.

The most common clinical finding is hepatosplenomegaly. Pruritus, gout, and mucocutaneous bleeding are occasionally seen.

Cytomegalic inclusion body disease (CIBD) is a series of signs and symptoms caused by cytomegalovirus infection, toxoplasmosis or other rare infections such as herpes or rubella viruses. It can produce massive calcification of the central nervous system, and often the kidneys.

Cytomegalic inclusion body disease is the most common cause of congenital abnormalities in the United States. It can also cause pneumonia and other diseases in immunocompromised patients, such as those with HIV/AIDS or recipients of organ transplants.

Various systems are affected.

- CNS abnormalities – microcephaly, mental retardation, spasticity, epilepsy, periventricular calcification

- Eye – choroidoretinitis and optic atrophy

- Ear – sensorineural deafness

- Liver – hepatosplenomegaly and jaundice due to hepatitis

- Lung – pneumonitis (interstitial pneumonitis)

- Heart – myocarditis

- Thrombocytopenic purpura, haemolytic anaemia

- Late sequelae in individuals asymptomatic at birth – hearing defects and reduced intelligence

Disease onset is typically in early infancy but may occur later in life. Children who have the classic form of Farber disease develop symptoms within the first few weeks of life. These symptoms may include moderately impaired mental ability and problems with swallowing. The liver, heart and kidneys may also be affected. Other symptoms may include vomiting, arthritis, swollen lymph nodes, swollen joints, joint contractures (chronic shortening of muscles or tendons around joints), hoarseness and xanthomas which thicken around joints as the disease progresses. Patients with breathing difficulty may require a breathing tube.

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.

The hallmark clinical and laboratory features include high fever, hepatosplenomegaly, lymphadenopathy, pancytopenia, liver dysfunction, disseminated intravascular coagulation, hypofibrinogenemia, hyperferritinemia, and hypertriglyceridemia. Despite marked systemic inflammation, the erythrocyte sedimentation rate (ESR) is paradoxically depressed, caused by low fibrinogen levels. The low ESR helps to distinguish the disorder from a flare of the underlying rheumatic disorder, in which case the ESR is usually elevated. A bone marrow biopsy or aspirate usually shows hemophagocytosis.

Farber disease (also known as Farber's lipogranulomatosis, ceramidase deficiency, "Fibrocytic dysmucopolysaccharidosis," and "Lipogranulomatosis") is an extremely rare (80 cases reported worldwide to this day) autosomal recessive lysosomal storage disease marked by a deficiency in the enzyme ceramidase that causes an accumulation of fatty material sphingolipids leading to abnormalities in the joints, liver, throat, tissues and central nervous system. Normally, the enzyme ceramidase breaks down fatty material in the body’s cells. In Farber Disease, the gene responsible for making this enzyme is mutated. Hence, the fatty material is never broken down and, instead, accumulates in various parts of the body, leading to the signs and symptoms of this disorder.

Macrophage-activation syndrome (MAS) is a severe, potentially life-threatening, complication of several chronic rheumatic diseases of childhood. It occurs most commonly with systemic-onset juvenile idiopathic arthritis (SoJIA). In addition, MAS has been described in association with systemic lupus erythematosus (SLE), Kawasaki disease, and adult-onset Still's disease. It is thought to be closely related and pathophysiologically very similar to reactive (secondary) hemophagocytic lymphohistiocytosis (HLH). The incidence of MAS is unknown as there is a wide spectrum of clinical manifestations, and episodes may remain unrecognized.

The signs and symptoms of CDA type III tend to be milder than those of the other types. Most affected individuals do not have hepatosplenomegaly, and iron does not build up in tissues and organs. In adulthood, abnormalities of a specialized tissue at the back of the eye (the retina) can cause vision impairment. Some people with CDA type III also have a blood disorder known as monoclonal gammopathy, which can lead to a cancer of white blood cells (multiple myeloma).

The anemia associated with CDA type II can range from mild to severe, and most affected individuals have jaundice, hepatosplenomegaly, and the formation of hard deposits in the gallbladder called bilirubin gallstones. This form of the disorder is usually diagnosed in adolescence or early adulthood. An abnormal buildup of iron typically occurs after age 20, leading to complications including heart disease, diabetes, and cirrhosis.

Congenital dyserythropoietic anemia type II (CDA II), or hereditary erythroblastic multinuclearity with positive acidified serum lysis test (HEMPAS) is a rare genetic anemia in humans characterized by hereditary erythroblastic multinuclearity with positive acidified serum lysis test.

Gaucher's disease (GD) has three common clinical subtypes. These subtypes have come under some criticism for not taking account of the full spectrum of observable symptoms (the phenotypes). Also, compound heterozygous variations occur which considerably increase the complexity of predicting disease course.

GD type I (non-neuropathic) is the most common and least severe form of the disease. Symptoms may begin early in life or in adulthood and mainly affect the liver, spleen, and bone. Enlarged liver and grossly enlarged spleen (together hepatosplenomegaly) are common; the spleen can rupture and cause additional complications. Skeletal weakness and bone disease may be extensive. Spleen enlargement and bone marrow replacement cause anemia, thrombocytopenia, and leukopenia. The brain and nervous system are not affected pathologically, but lung and, rarely, kidney impairment may occur. Patients in this group usually bruise easily (due to low levels of platelets) and experience fatigue due to low numbers of red blood cells. Depending on disease onset and severity, type I patients may live well into adulthood. The range and severity of symptoms can vary dramatically between patients.

GD type II (acute infantile neuropathic) typically begins within 6 months of birth and has an incidence rate around one 1 in 100,000 live births. Symptoms include an enlarged liver and spleen, extensive and progressive brain damage, eye movement disorders, spasticity, seizures, limb rigidity, and a poor ability to suck and swallow. Affected children usually die by age two.

GD type III (chronic neuropathic) can begin at any time in childhood or even in adulthood, and occurs in about one in 100,000 live births. It is characterized by slowly progressive, but milder neurologic symptoms compared to the acute or type II version. Major symptoms include an enlarged spleen and/or liver, seizures, poor coordination, skeletal irregularities, eye movement disorders, blood disorders including anemia, and respiratory problems. Patients often live into their early teen years and adulthood.

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.

LRBA deficiency presents as a syndrome of autoimmunity, lymphoproliferation, and humoral immune deficiency. Predominant clinical problems include idiopathic thrombocytopenic purpura (ITP), autoimmune hemolytic anemia (AIHA), and an autoimmune enteropathy. Before the discovery of these gene mutations, patients were diagnosed with common variable immune deficiency (CVID), which is characterized by low antibody levels and recurrent infections. Infections mostly affect the respiratory tract, as many patients suffer from chronic lung disease, pneumonias, and bronchiectasis. Lymphocytic interstitial lung disease (ILD) is also observed, which complicates breathing and leads to impairment of lung function and mortality. Infections can also occur at other sites, such as the eyes, skin and gastrointestinal tract. Many patients suffer from chronic diarrhea and inflammatory bowel disease. Other clinical features can include hepatosplenomegaly, reoccurring warts, growth retardation, allergic dermatitis, and arthritis. Notably, LRBA deficiency has also been associated with type 1 diabetes mellitus. There is significant clinical phenotypic overlap with disease caused by CTLA4 haploinsufficiency. Since LRBA loss results in a loss of CTLA4 protein, the immune dysregulation syndrome of LRBA deficient patients can be attributed to the secondary loss of CTLA4. Because the predominant features of the disease include autoantibody-mediated disease (AIHA, ITP), Treg defects (resembling those found in CTLA4 haploinsufficient patients), autoimmune infiltration (of non-lymphoid organs, also resembling that found in CTLA4 haploinsufficient patients), and enteropathy, the disease has been termed LATAIE for LRBA deficiency with autoantibodies, Treg defects, autoimmune infiltration, and enteropathy.

This condition causes severe infections. it is characterized by elevated immunoglobulins that function poorly.

Other symptoms are:

- Bronchiectasis

- Hepatosplenomegaly

- Pyoderma

- Emphysema

- Diarrhea

LRBA deficiency is a rare genetic disorder of the immune system. This disorder is caused by a mutation in the gene "LRBA". LRBA stands for “Lipopolysaccharide (LPS)-responsive vesicle trafficking, beach- and anchor-containing” gene. This condition is characterized by autoimmunity, lymphoproliferation, and immune deficiency. It was first described by Gabriela Lopez-Herrera from University College London in 2012. Investigators in the laboratory of Dr. Michael Lenardo at National Institute of Allergy and Infectious Diseases, the National Institutes of Health and Dr. Michael Jordan at Cincinnati Children’s Hospital Medical Center later described this condition and therapy in 2015.

Acanthocheilonemiasis is a rare tropical infectious disease caused by a parasite known as "Acanthocheilonema perstans". It can cause skin rashes, abdominal and chest pains, muscle and joint pains, neurological disorders and skin lumps. It is mainly found in Africa. The parasite is transmitted through the bite of small flies. Studies show that there are elevated levels of white blood cells.

Acanthocheilonemiasis belongs to a group of parasitic diseases known as filarial disease (nematode), all of which are classified as Neglected Tropical Diseases. Filarial disease results when microfilariae, which are nematode larvae, reach the lymphatic system; microfilariae reside in the serous cavities of humans. They have a five-stage life cycle that includes birth to thousands of live microfilariae within the host (i.e. human body), and then translocation via blood meal to the dermis layer of the skin. It is here that microfilariae cause major symptoms, which are edema and thickening of the skin and underlying connective tissues. It can also cause skin rashes, abdominal and chest pains, muscle (myalgia) and joint pains, neurological disorders and skin lumps. In addition, it causes spleen and liver enlargement, which is called hepatosplenomegaly. Studies show elevated levels of leukocytes, or white blood cells, which is referred to as eosinophilia. It is mainly found in Africa. The parasite is transmitted through the bite of small flies ("A. coliroides").

Peripheral blood, bone marrow, spleen, and liver are most common, but any organ or tissue can be infiltrated by neutrophils.

Congenital dyserythropoietic anemia type III (CDA III) is a rare autosomal dominant disorder characterized by macrocytic anemia, bone marrow erythroid hyperplasia and giant multinucleate erythroblasts. New evidence suggests that this may be passed on recessively as well.