Type 1 In individuals with Type 1<unk> , the disorder is caused by a mutation at the AGPAT2 gene encoding 1-acylglycerol-3-phosphate O-acyltransferase 2 and located at 9q34.3. This enzyme catalyzes the acylation of lysophosphatidic acid to form phosphatidic acid, which is important in the biosynthesis of fats. This enzyme is highly expressed in adipose tissue, so it can be concluded that when the enzyme is defective in<unk> , lipids cannot be stored in the adipose tissue. Type 2 In those who have Type 2<unk> , a mutation in the BSCL2 gene encoding the Seipin protein and located at 11q13. This gene encodes a protein, Seipin, whose function is unknown. Expression of mRNA for the seipin protein is high in the brain, yet low in adipose tissues. Additionally, patients which have mutations in this protein have a higher incidence of mental retardation and lack mechanically active adipose tissue, which is present in those with AGPAT2 mutations. Type 3 Type 3<unk>  involves a mutation in the CAV1 gene. This gene codes for the Caveolin protein, which is a scaffolding membrane protein. This protein plays a role in lipid regulation. High levels of Cav1 are normally expressed in adipocytes. Thus, when the CAV1 gene mutates the adipocytes do not have Cav1 and are unable to properly regulate lipid levels. Type 4 A mutation in the PTRF gene causes Type 4<unk> . This gene codes for a protein called polymerase I and transcript release factor. One of the roles the PTRF product has it to stabilize and aid in formation of caveolae. Thus, the mechanism is similar to Type 3, in that the caveolae are unable to properly form and carry out their role in lipid regulation in both. Types 3 and 4 are two different mutations but they share a common defective pathway.
Congenital generalized lipodystrophy
Familial partial lipodystrophy
Hypohidrotic ectodermal dysplasia
Acquired generalized lipodystrophy
Familial multiple lipomatosis
X-linked hypertrichosis
Yemenite deaf-blind hypopigmentation syndrome
Encephalocraniocutaneous lipomatosis