The link between blue baby syndrome and nitrates in drinking water is widely accepted, but some studies indicate that other contaminants, or dietary nitrate sources, may also play a role in the syndrome. Diagnosis
When diagnosing blue baby syndrome, it is important to perform a thorough history and physical exam. When obtaining the history, it is important to determine the timing of symptoms and to ask about risk factors/exposures, such as prenatal history or access to well-water. On physical exam it is important to visualize where the cyanosis is present to differentiate between peripheral and central cyanosis. Central cyanosis is typically visible as a blueish discoloration over the entire body and mucous membranes. In contrast, peripheral cyanosis typically has a blueish discoloration over the extremities. Cyanosis can be noted in babies around the lips, tongue, and sublingual area, where the skin is thinnest. In addition, it is important to observe the infant for signs of respiratory distress, visualized as nasal flaring, subcostal retractions, etc. Examination should include a respiratory and cardiac assessment.One of the key tools in diagnosing is a pulse oximeter to determine oxygen saturation. While severe cyanosis can be easily noticed, an oxygen saturation as low as 80% causes only mild clinical cyanosis that is difficult to see. Additionally an arterial blood gas is useful, for example in the case of methemoglobinemia the PO2 can be expected to be normal even with a low oxygen saturation.
Dermatopolymyositis  is a family of myositis disorders that includes polymyositis and dermatomyositis. As such, it includes both a distinctive skin rash and progressive muscular weakness. It is a rare disease. References


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