Amino acid synthesis deficiencies

In recent years the number of disorders known to affect amino acid synthesis has grown rapidly. Nor is it just the number of disorders that has increased: the associated clinical phenotypes have also expanded spectacularly, primarily due to the advances of next generation sequencing diagnostics. In contrast to the "classical" inborn errors of metabolism in catabolic pathways, in which elevated levels of metabolites are easily detected in body fluids, synthesis defects present with low values of metabolites or, confusingly, even completely normal levels of amino acids. This makes the biochemical diagnosis of this relatively new group of metabolic diseases challenging. Defects in the synthesis pathways of serine metabolism, glutamine, proline and, recently, asparagine have all been reported. Although these amino acid synthesis defects are in unrelated metabolic pathways, they do share many clinical features. In children the central nervous system is primarily affected, giving rise to (congenital) microcephaly, early onset seizures and varying degrees of mental disability. The brain abnormalities are accompanied by skin disorders such as cutis laxa in defects of proline synthesis, collodion-like skin and ichthyosis in serine deficiency, and necrolytic erythema in glutamine deficiency. Hypomyelination with accompanying loss of brain volume and gyration defects can be observed on brain MRI in all synthesis disorders. In adults with defects in serine or proline synthesis, spastic paraplegia and several forms of polyneuropathy with or without intellectual disability appear to be the major symptoms in these late-presenting forms of amino acid disorders. This review provides a comprehensive overview of the disorders in amino acid synthesis

Noma in Laos: stigma of severe poverty in rural Asia.

Noma, or cancrum oris, is a debilitating necrotizing ulcerative stomatitis that destroys the mouth and face. It usually starts in early childhood and is associated with severe poverty, malnutrition, and infections. It is most frequently described from sub-Saharan Africa but is under-reported. There have been very few reports from Asia. We describe the clinical and social features of a series of 12 patients with noma from remote poor villages in rural Lao People's Democratic Republic (Laos). Noma is an ominous stigma of severe poverty and the description of this disease emphasizes the importance of poverty reduction and nutritional improvement in Lao development. In the meantime, more awareness of the problem and the importance of early therapy in acute noma by primary health care workers may reduce mortality and prevent progression to severe disfigurement