Study of People With Generalized Arterial Calcification of Infancy (GACI) or Autosomal Recessive Hypophosphatemic Rickets Type 2 (ARHR2)

Background: Generalized Arterial Calcification of Infancy (GACI) is a very rare disorder. It can be fatal before birth or by age 6 months. Anumber of people with GACI survive into adulthood. Those adults suffer from side effects of the disease, including rickets. It is unknown how common the disease Autosomal Recessive Hypophosphatemic Rickets Type 2 (ARHR2) is. It also has side effects. GACI and ARHR2 are usually caused by the mutations in the same gene. There are no approved treatments for the two diseases. Researchers want to study people with these diseases and their family members. This may help understand these rare and unique diseases better. The data could lead to new treatments for GACI and ARHR2. Objectives: To better understand the progression of GACI and ARHR2 and how genes might play a role in them. Eligibility: People with GACI or ARHR2, both living and deceased, and their parents and siblings. Design: Participants will allow researchers to access their medical records. They will give this consent by mail, email, or fax. Data will be taken from the records. Participants names will not be used. Instead, they will be identified by a code. Participants may give a blood sample. If a participant withdraws from the study, their data and samples will be destroyed. However, the coded clinical data in the official medical record and data in databases will NOT be destroyed.

* INCLUSION \& EXCLUSION CRITERIA: Based upon study purpose, participants enrolled in this protocol must: 1. Have genetic confirmation of one of the following: 1. GACI due to ENPP1 or ABCC6 mutations 2. ARHR2 due to ENPP1 mutations 3. PXE due to ABCC6 or ENPP1 mutations AND/OR Carry the clinical diagnosis of GACI, ARHR2 or PXE 2. Consent or, if applicable, assent to participate in the study 3. Have sufficient chart information to allow for the completion of at least one of the protocol s objectives.