A rare glycogen storage disease with fetal or neonatal onset of severe cardiomyopathy with non-lysosomal glycogen accumulation and fatal outcome in infancy. Patients present with massive cardiomegaly, severe cardiac and respiratory complications and failure to thrive. Non-specific facial dysmorphism, bilateral cataracts, macroglossia, hydrocephalus, enlarged kidneys and skeletal muscle involvement have been reported in some cases.

While most people with familial hypertrophic cardiomyopathy are symptom-free or have only mild symptoms, this condition can have serious consequences. It can cause abnormal heart rhythms (arrhythmias) that may be life threatening. People with familial hypertrophic cardiomyopathy have an increased risk of sudden death, even if they have no other symptoms of the condition. A small number of affected individuals develop potentially fatal heart failure, which may require heart transplantation.\n\nThe symptoms of familial hypertrophic cardiomyopathy are variable, even within the same family. Many affected individuals have no symptoms. Other people with familial hypertrophic cardiomyopathy may experience chest pain; shortness of breath, especially with physical exertion; a sensation of fluttering or pounding in the chest (palpitations); lightheadedness; dizziness; and fainting.\n\nIn familial hypertrophic cardiomyopathy, cardiac thickening usually occurs in the interventricular septum, which is the muscular wall that separates the lower left chamber of the heart (the left ventricle) from the lower right chamber (the right ventricle). In some people, thickening of the interventricular septum impedes the flow of oxygen-rich blood from the heart, which may lead to an abnormal heart sound during a heartbeat (heart murmur) and other signs and symptoms of the condition. Other affected individuals do not have physical obstruction of blood flow, but the pumping of blood is less efficient, which can also lead to symptoms of the condition. Familial hypertrophic cardiomyopathy often begins in adolescence or young adulthood, although it can develop at any time throughout life.\n\nNonfamilial hypertrophic cardiomyopathy tends to be milder. This form typically begins later in life than familial hypertrophic cardiomyopathy, and affected individuals have a lower risk of serious cardiac events and sudden death than people with the familial form.\n\nHypertrophic cardiomyopathy is a heart condition characterized by thickening (hypertrophy) of the heart (cardiac) muscle. When multiple members of a family have the condition, it is known as familial hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy also occurs in people with no family history; these cases are considered nonfamilial hypertrophic cardiomyopathy. 

The main cause of respiratory distress syndrome (RDS) in premature infants is a developmental deficiency of pulmonary surfactant. The frequency of RDS is inversely proportional to gestational age. However, not all infants born prematurely develop RDS, suggesting that there may be susceptibility factors. Because multiple factors can contribute to the pathogenesis of RDS specifically in premature infants, the etiology is considered to be multifactorial (summaries by Ramet et al., 2000; Clark and Clark, 2005). Pathogenic germline mutations in several genes involved in surfactant metabolism, including SFTPB (178640) and SFTPC (178620), can cause clinical features of respiratory distress syndrome in term neonates, children, and adults, disorders referred to as 'surfactant metabolism dysfunction' (see, e.g., SMDP1, 265120). Susceptibility to the development of RDS in premature infants may be associated with polymorphisms in surfactant genes, such as surfactant protein A1 (SFTPA1; 178630), SFTPB, and SFTPC (see MOLECULAR GENETICS).

Ogden syndrome (OGDNS) is an X-linked neurodevelopmental disorder characterized by postnatal growth failure, severely delayed psychomotor development, variable dysmorphic features, and hypotonia. Many patients also have cardiac malformations or arrhythmias (summary by Popp et al., 2015).

LMPHM7 is an autosomal dominant disorder with variable expressivity. Some patients may develop severe nonimmune lymphatic-related hydrops fetalis (LRHF) in utero, resulting in early death, whereas others may have milder manifestations, such as atrial septal defect (ASD) or varicose veins as adults. The hydrops and/or swelling improves spontaneously in those who survive the neonatal period (summary by Martin-Almedina et al., 2016). For a discussion of genetic heterogeneity of lymphatic malformation, see 153100.