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Patients with generalized arterial calcification of infancy (GACI) develop vascular calcifications early in life. About half of them die within the first six months despite optimal medical care. A subset of those who survive eventually develop hypophosphatemic rickets. Since hypophosphatemia and hyperphosphaturia have been previously associated with increased survival in GACI patients, physicians often avoid phosphate repletion as treatment for rickets. As a consequence, GACI patients develop severe rachitic complications such as short stature and skeletal deformities. It appears that the recognition of hypophosphatemia later in life in some GACI patients is a consequence of having survived the first few months of life, and not the cause of their survival per se. Here, we report the long-term follow-up of a GACI patient who was phosphate-repleted for his rickets for more than seven years without worsening of vascular calcification.

Pseudoxanthoma elasticum (PXE) is an autosomal recessive disease affecting tissues rich in elastic fibers such as the skin, retina, and cardiovascular system. Mutations in the ABCC6 gene are known to be causative in most patients. Generalized arterial calcification of infancy (GACI) is characterized by extensive hydroxyapatite deposits in the internal elastic laminae in large and medium-sized arteries, leading to arterial stenoses and early and severe myocardial ischemia. GACI has been found to be primarily caused by mutations in the ENPP1 gene. We report two brothers born to unrelated parents. The elder developed uncomplicated PXE in adolescence and harbored mutations in the ABCC6 gene. The younger child died of a condition strikingly reminiscent of GACI at 15 months of age. This case of GACI was independent of mutations in the ENPP1 gene but was probably related to ABCC6 mutations. We demonstrate that matrix Gla protein and fetuin-A, involved in PXE, are also expressed in this case of GACI. These proteins could act as local and systemic inhibitors to limit the extension of mineralization. This report emphasizes concurrently that ABCC6 may be a relevant candidate gene in some cases of GACI with no mutations in the ENPP1 gene, and that GACI may be an atypical and severe end of the vascular phenotype spectrum of PXE.

Generalized arterial calcification of infancy (GACI) is a rare autosomal recessive disease caused by mutations in ENPP1. Due to extensive calcification of the arterial media associated with intimal proliferation leading to vascular occlusion, most affected children die within the first 6 months of life. We report on two Taiwanese siblings with an identical genotype, but different clinical course. The male sibling developed heart failure and severe hypertension, and died at the age of 6 weeks despite of treatment with bisphosphonates, ACE inhibitors, and hydralazine. The subsequent female, who was monitored closely pre- and post-natally, is having an uncomplicated clinical course up to the age of 1(1/2) year now. There were similar characteristic sonographic and roentgenographic findings in both siblings in early infancy. In both siblings, the same compound heterozygous mutations (c.1025G > T [p.Gly342Val] and c.1112A > T [Tyr371Phe]) in ENPP1 were identified. Despite the same genotype and similar sonographic and radiographic features in early infancy, the phenotype of GACI can vary to a great extent within one family.