MIAMI BEACH, Fla. - When attempting to diagnose milk allergies and lactose intolerance in infants or young children, the two can be frequently misdiagnosed, according to a Florida pediatrician who has spent the last decade studying the differences between cow milk allergies and lactose intolerance.
Milk allergies can manifest themselves in many ways. They occur in infants and young children rather than adults, predominantly affect the gastrointestinal tract rather than other systems, will usually affect only one system at a time and have a high degree of sensitivity to exams like total IgE, radioallergosorbent test (RAST) score and skin reactivity.
In comparison, lactose intolerance is basically a benign gastrointestinal disorder caused by a deficiency in production of intestinal lactase enzymes relative to the quantity of lactose in the diet. Its most dangerous by-products are Heiner's Syndrome - or milk-induced chronic pulmonary disease - and anemia.
Cow's milk allergy (CMA) is primarily a childhood disease with onset occurring mostly during infancy, said Sami L. Bahna, MD, professor of pediatrics and medicine and co-director of the Allergy and Immunology Training Program at the University of South Florida's All Children's Hospital in St. Petersburg.
CMA prevalence among all bottle-fed infants during their first years of life can be about 3% to 5%, with high figures for those who have family histories of atopy, prematurity or gastrointestinal disorders such as cystic fibrosis or celiac disease. Hypersensitivity reactions are precipitated by milk proteins, that range from 2.8 g/dL to 4.1g/dL, with an average of 3.3 g/dL.
Cow's milk proteins (CMP) are divided into caseins (76%-86%) and whey proteins (14%-42%); the latter include b-lactoglobulin (7%-12%), a-lactalbumin (2%-5%), serum albumin (0.7%-1.3%) and serum immunoglobulins (1.4%-2.8%). Casein and b-lactoglobulin are the most allergic components as well as the most heat-resistant, said Bahna.
Although ingestion is by far the principal route of exposure, severe reactions through skin contact or by inhalation were documented by Bahna. An infant with severe CMA was reported to have had two episodes of definite systemic anaphylaxis following application of a diaper rash ointment that contained 5% calcium caseinate. Another case report was an adult who had gastrointestinal CMA since childhood and developed severe episodes of bronchospasm, all believed to be the result of exposure to milk through inhalation, said Bahna.
Heiner's syndrome is a rare disorder that was first described in 1960. Typically, infants fed with cow's milk present with coughing, wheezing and sometimes hemoptysis. In some patients, vasculitis may be severe enough to cause bleeding in the aveolars and result in pulmonary hemosiderosis. The symptoms improve usually within a few days of discontinuing milk, but the pulmonary infiltrate may not resolve itself for several weeks, said Bahna.
Lactose intolerance (LI) usually occurs in adults, particularly Asians, Native Alaskans and blacks. Those affected can develop gastrointestinal symptoms shortly after ingesting milk. Except in the case of congenital lactase deficiency, avoidance of lactose is rarely necessary in these cases. In the delayed-onset type of LI, although the affliction continues for life, most patients can still tolerate small amounts of lactose.
There are three types of lactase deficiency. Infants with congenital lactase deficiency cannot tolerate any human or milk-based formula. In delayed onset deficiency, the production of lactase begins to drop early in childhood but the symptoms may not appear until teenage or the early adult years. Secondary lactase deficiency is caused by small intestinal mucosal disease. If the latter is acute, such as in viral and bacterial gastroenteritis, lactose production usually normalizes within days of recovery. But the degrees of lactase deficiency and mucosal damage do not always correlate, said Bahna.
"CMA and LI are two disorders that can often be mistaken for one another because the root of diagnosing their symptoms is milk," said Bahna. "Pediatricians should be aware of this - but many times are not. CMA and LI don't lend themselves to simple black-and-white solutions."
For more information:
- Bahna SL. Milk allergy. Presented at the 33rd Annual Miami Children's Hospital Pediatric Postgraduate Course. Jan. 24-30. Miami Beach, Fla.
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