Malonyl-CoA decarboxylase deficiency (MCD), or Malonic aciduria is an autosomal-recessive metabolic disorder caused by a genetic mutation that disrupts the activity of Malonyl-Coa decarboxylase. This enzyme breaks down Malonyl-CoA (a fatty acid precursor and a fatty acid oxidation blocker) into Acetyl-CoA and carbon dioxide.

The signs and symptoms of this disorder typically appear in early childhood. Almost all affected children have delayed development. Additional signs and symptoms can include weak muscle tone (hypotonia), seizures, diarrhea, vomiting, and low blood sugar (hypoglycemia). A heart condition called cardiomyopathy, which weakens and enlarges the heart muscle, is another common feature of malonyl-CoA decarboxylase deficiency.

Some common symptoms in Malonyl-CoA decarboxylase deficiency, such as cardiomyopathy and metabolic acidosis, are triggered by the high concentrations of Malonyl-CoA in the cytoplasm. High level of Malonyl-CoA will inhibits β-oxidation of fatty acids through deactivating the carrier of fatty acyl group, CPT1, and thus, blocking fatty acids from going into the mitochondrial matrix for oxidation.

A research conducted in Netherlands has suggested that carnitine supplements and a low fat diet may help to reduce the level of malonic acid in our body.

Microlissencephaly is listed in Orphanet database as a rare disease. There is no much information available about the epidemiology of microlissencepahly in literature. A PhD thesis has estimated the prevalence of microlissencepahly in South–Eastern Hungary between July 1992 and June 2006 to be a case every 91,000 live births (0.11:10,000).

The genetic basis and pathophysiology of microlissencephaly are still not completely understood.

Most cases of microlissencephaly are described in consanguineous families suggesting an autosomal recessive inheritance. Mutation of "RELN" gene or "CIT" could cause MLIS. Human NDE1 mutations and mouse Nde1 loss lead to cortical lamination deficits, which, together with reduced neuronal production cause microlissencephaly. Homozygous frameshift mutations in "NDE1" gene was found to cause microlissencephaly with up to 90% reduction in brain mass and seizures starting early in life. Some other disease-causing genes include: "KATNB1" and "WDR62". It is hypothesized that the "KATNB1"-associated microlissencephaly is the result of a combined effect of reduced neural progenitor populations and impaired interaction between the "Katanin P80 subunit" (encoded by "KATNB1") and "LIS1" ( "PAFAH1B1"), a protein mutated in type 1 lissencephaly. Missense mutation in "ACTG1" gene was identified in three cases of microlissencephaly. ACTG1 is the same gene that, when mutated, causes Baraitser-Winter syndrome. A loss-of-function mutation in the "Doublesex- and Mab-3–Related Transcription factor A2" (DMRTA2, also known as DMRT5) gene has been reported in a case of microlissencephaly, implicating DMRTA2 as a critical regulator of cortical neural progenitor cell dynamics.

Microlissencepahly is considered a tubulinopathy (tubulin gene defect) i.e. is caused by mutation in tubulin genes, mainly "TUBA1A" and less commonly "TUBB2B", "TUBB3", "TUBA3E" and "TUBG1". Central pachygyria, polymicrogyria are more commonly seen in patients with defects in "TUBB2B", "TUBB3", and "TUBB5". This implys the critical role of microtubule cytoskeleton in the pathophysiology of microlissencephaly as well as other neuronal migration disorders.

Congenital infections like cytomegalovirus are also known to cause microlissencephaly.

Both microlissencephaly and microcephaly with simplified gyral pattern result from either decreased stem cell proliferation or increased apoptosis in the germinal zone of the cerebral cortex.

Macular corneal dystrophy is inherited in autosomal recessive fashion and is thought to be caused by the lack or abnormal configuration of keratan sulfate. Most cases of MCD are caused by mutations in CHST6 gene.

The gene CHST6 is a carbohydrate sulfotransferase encoding an enzyme designated corneal N-acetylglucosamine-6-sulfotransferase. In MCD type I, various mutations lead to inactivation of the enzyme, in MCD type II, inactivation is caused by large deletions and/or replacements in the gene.

Minimal change disease is most common in very young children but can occur in older children and adults. It is by far the most common cause of nephrotic syndrome in children between the ages of 1 and 7, accounting for the majority (about 90%) of these diagnoses. Among teenagers who develop nephrotic syndrome, it is caused by minimal change disease about half the time. It can also occur in adults but accounts for less than 20% of adults diagnosed with nephrotic syndrome. Among children less than 10 years of age, boys seem to be more likely to develop minimal change disease than girls. Minimal change disease is being seen with increasing frequency in adults over the age of 80.

People with one or more autoimmune disorders are at increased risk of developing minimal change disease. Having minimal change disease also increases the chances of developing other autoimmune disorders.

Focal segmental glomerulosclerosis (FSGS) is a cause of nephrotic syndrome in children and adolescents, as well as a leading cause of kidney failure in adults. It is also known as "focal glomerular sclerosis" or "focal nodular glomerulosclerosis". It accounts for about a sixth of the cases of nephrotic syndrome. (Minimal change disease (MCD) is by far the most common cause of nephrotic syndrome in children: MCD and primary FSGS may have a similar cause.)

There are currently several known genetic causes of the hereditary forms of FSGS.

Some researchers found SuPAR as a cause of FSGS.

Another gene that has been associated with this syndrome is the COL4A5 gene.

Macular corneal dystrophy, also known as Fehr corneal dystrophy named for German ophthalmologist Oskar Fehr (1871-1959), is a rare pathological condition affecting the stroma of cornea. The first signs are usually noticed in the first decade of life, and progress afterwards, with opacities developing in the cornea and attacks of pain. The condition was first described by Arthur Groenouw in 1890.

Minimal change disease has been called by many other names in the medical literature, including minimal change nephropathy, minimal change nephrosis, minimal change nephrotic syndrome, minimal change glomerulopathy, foot process disease (referring to the foot processes of the podocytes), nil disease (referring to the lack of pathologic findings on light microscopy), nil lesions, lipid nephrosis, and lipoid nephrosis.

Nephrotic syndrome can be associated with a series of complications that can affect an individual’s health and quality of life:

- Thromboembolic disorders: particularly those caused by a decrease in blood antithrombin III levels due to leakage. Antithrombin III counteracts the action of thrombin. Thrombosis usually occurs in the renal veins although it can also occur in arteries. Treatment is with oral anticoagulants (not heparin as heparin acts via anti-thrombin 3 which is lost in the proteinuria so it will be ineffective.) Hypercoagulopathy due to extravasation of fluid from the blood vessels (edema) is also a risk for venous thrombosis.

- Infections: The increased susceptibility of patients to infections can be a result of the leakage of immunoglobulins from the blood, the loss of proteins in general and the presence of oedematous fluid (which acts as a breeding ground for infections). The most common infection is peritonitis, followed by lung, skin and urinary infections, meningoencephalitis and in the most serious cases septicaemia. The most notable of the causative organisms are "Streptococcus pneumoniae" and "Haemophilus influenzae".

- Acute kidney failure due to hypovolemia: the loss of vascular fluid into the tissues (edema) produces a decreased blood supply to the kidneys that causes a loss of kidney function. Thus it is a tricky task to get rid of excess fluid in the body while maintaining circulatory euvolemia.

- Pulmonary edema: the loss of proteins from blood plasma and the consequent fall in oncotic pressure causes an abnormal accumulation of liquid in the lungs causing hypoxia and dyspnoea.

- Hypothyroidism: deficiency of the thyroglobulin transport protein thyroxin (a glycoprotein that is rich in iodine and is found in the thyroid gland) due to decreased thyroid binding globulin.

- Hypocalcaemia: lack of 25-hydroxycholecalciferol (the way that vitamin D is stored in the body). As vitamin D regulates the amount of calcium present in the blood a decrease in its concentration will lead to a decrease in blood calcium levels. It may be significant enough to cause tetany. Hypocalcaemia may be relative; calcium levels should be adjusted based on the albumin level and ionized calcium levels should be checked.

- Microcytic hypochromic anaemia: iron deficiency caused by the loss of ferritin (compound used to store iron in the body). It is iron-therapy resistant.

- Protein malnutrition: this occurs when the amount of protein that is lost in the urine is greater than that ingested, this leads to a negative nitrogen balance.

- Growth retardation: can occur in cases of relapse or resistance to therapy. Causes of growth retardation are protein deficiency from the loss of protein in urine, anorexia (reduced protein intake), and steroid therapy (catabolism).

- Vitamin D deficiency can occur. Vitamin D binding protein is lost.

- Cushing's Syndrome

The treatment of nephrotic syndrome can be symptomatic or can directly address the injuries caused to the kidney.

Large B-cell lymphoma arising in HHV8-associated multicentric Castleman's disease is a type of large B-cell lymphoma, recognized in the WHO 2008 classification. It is sometimes called the plasmablastic form of multicentric Castleman disease. It has sometimes been confused with plasmablastic lymphoma in the literature, although that is a dissimilar specific entity. It has variable CD20 expression and unmutated immunoglobulin variable region genes.

Castleman disease (CD) is a lymphoproliferative disorder of unknown cause. CD is associated with an increased risk of B-cell lymphoma.

Human herpesvirus 8 (HHV-8), also known as Kaposi sarcoma-associated herpesvirus (KSHV) has been found in some cases of multicentric Castleman disease (MCD). The HHV8 can give rise to an increased number of plasmablast cells within the mantle zone of B-cell follicles. These plasmablasts express IgM-immunoglobulin light chains, most often of lambda subtype. These plasmablasts can give rise to a spectrum of abnormalities including progression to microlymphoma (microscopic clusters of plasmablast cells) or clinical lymphoma.

This type of lymphoma is predominantly seen in acquired immunodeficiencies, including acquired immunodeficiency syndrome (AIDS) but it can also occur in immunosuppression such as with organ transplantation or the elderly. The plasmablasts do not show rearranged immunoglobulin genes, and typically lack EBV infection.

The disease predominantly affects lymph nodes and the spleen, a pattern dissimilar to plasmablastic lymphoma of the oral cavity of AIDS which is not associated with HHV-8 infection. Despite traditional chemotherapy with CHOP (cyclophosphamide, doxorubicin, prednisone, vincristine), and the possible addition of antiviral therapy and inhibition of specific cellular targets including the use of rituximab, the prognosis in this lymphoma has been poor.

This lymphoma subtype has sometimes been confused with plasmablastic lymphoma in the literature, although that is a dissimilar specific entity. Similarly, this subtype is considered distinct from other lymphomas which have a plasmablastic immunophenotype such as primary effusion lymphoma, ALK+ large B-cell lymphoma, and extracavitary HHV–8-positive lymphoma.

HHV8 is also associated with Kaposi's sarcoma and with another subtype of lymphoma, primary effusion lymphoma, previously called body cavity-based lymphoma.

Lymph node abnormalities and organ dysfunction in Castleman disease are caused by excessive secretion of cytokines. IL-6 is the most commonly elevated cytokine, but some affected people may have normal IL-6 levels and present with non-iron-deficient microcytic anemia.

The release of these cytokines is caused by infection with Human herpesvirus 8 in HHV-8-associated MCD. The cause of the release of cytokines in idiopathic MCD has been hypothesized to be caused by either a somatic mutation, a germline genetic mutation, or a non-HHV-8-virus.

Castleman disease, also known as giant lymph node hyperplasia, lymphoid hamartoma, or angiofollicular lymph node hyperplasia, is a group of uncommon lymphoproliferative disorders that share common lymph node histological features. The disease is named after Benjamin Castleman.

Castleman's disease has two main forms: It may be localized to a single lymph node (unicentric) or occur systemically (multicentric).

The unicentric form can usually be cured by surgically removing the lymph node, with a 10-year survival of 95%.

Multicentric Castleman disease (MCD) involves hyperactivation of the immune system, excessive release of proinflammatory chemicals (cytokines), proliferation of immune cells (B cells and T cells), and multiple organ system dysfunction. Castleman disease must be distinguished from other disorders that can demonstrate "Castleman-like" lymph node features, including reactive lymph node hyperplasia, autoimmune disorders, and malignancies. Multicentric Castleman's disease is associated with lymphoma and Kaposi's sarcoma.