Group 5.3 Metabolic disorders 
PH has been reported in a few cases of type Ia glycogen storage disease, a rare autosomal-recessive disorder caused by a deficiency of glucose-6-phosphatase [93-95]. The mechanisms of PH are uncertain but portocaval shunts, atrial septal defects, severe restrictive pulmonary function defects or thrombosis are thought to play a role. In one case, autopsy findings revealed the presence of plexiform lesions [96].
Gaucher’s disease is a rare disorder characterized by a deficiency of lysosomal B glucosidase, which results in an accumulation of glucocerebroside in reticuloendothelial cells. In a study of 134 patients with Gaucher’s disease who were systematically screened by echocardiography, PH was not uncommon [97]. In this setting, several potential mechanisms for PH have been suggested, including interstitial lung disease, chronic hypoxemia, capillary plugging by Gaucher cells and splenectomy [97,98].
The association between thyroid diseases and PH has been reported in some studies [99]. A prospective study of 63 consecutive adult patients with PAH found a prevalence of autoimmune thyroid disease, including both hypothyroidism and hyperthyroidism, in 49%, suggesting that these conditions may share a common immunogenetic susceptibility [100].