A Medical Whodunnit: 16 Month Old Female with Failure to Thrive

A couple of weeks ago I received a telephone call from SS, one of my daughter’s close friends from college.  SS, who lives in New York City, called my daughter, who lives in California, because she was concerned about her younger sister’s (RS) daughter, KS .  RS had been worried about her daughter’s growth.  RS told her sister SS about the problem and SS promptly called my daughter; I suspect SS called my daughter because the daughter of a pediatrician would be expected to know almost as much as a pediatrician.  Right?  Anyway, my daughter called me and I was warned to be expecting a phone call from SS, which I got the next day.  SS wanted to know if I would be willing to talk with her sister.  Of course I agreed and talked with RS the next day.  I learned that KS was 16 months old and had  been  diagnosed with failure to thrive (FTT).  RS wanted to know what FTT was and what I thought should be done.  The situation was a bit complicated because RS lives in the Netherlands and was just visiting the U.S.  The family (RS, her husband, and 2 daughters, MS, age 4 years, and KS) has health insurance in the Netherlands but no coverage in the U.S.  The diagnosis of FTT had been made by a pediatrician in New York who recommended that a large number of laboratory studies be carried out as soon as possible.  One question RS had for me was whether the tests needed to be done immediately or could wait until the family returned to the Netherlands in about 2 weeks; the pediatrician estimated that the tests would cost about $5000-$10,000 (blood work, x-rays, and MRI, etc).

The Medical History

I first told RS that I would be happy to discuss things with her but that she needed to understand that it is always risky to get “curbside” consultations and that without actually seeing a patient, it is difficult for a physician to give a well-reasoned opinion,  and that my advice should be considered in that light.  KS was born full-term after an uneventful pregnancy.  There were no problems at birth and initially the infant seemed to do very well, following the 50% for height and weight until about age 6 months.  RS and her husband were of average height and their older daughter, MS was at about 60% for height and weight.  The infant was being exclusively breast-fed. After age 6 months, the infant slowed her growth rate, falling to about 40% for height and 5% for weight by age 1 year; at age 15 months, the height was still at about 40% but the weight percentile fell further, to about 2%.  At no time did the infant show actual weight loss.  KS seemed to be feeding well and was a happy baby although her development seemed to be a bit slower that that of her older sister; KS was babbling but still not walking.

The New York pediatrician who  saw KS  made the diagnosis of FTT based on the infant’s weight and the history of slow weight gain.  The pediatrician felt the physical examination was normal except for the weight and perhaps, slightly delayed motor development, and slightly decreased muscle tone.  As discussed above, the pediatrician recommended a series of studies but felt they could be delayed a few weeks (until the family returned to the Netherlands.  The pediatrician did order a complete blood count and basic blood chemistry tests (electrolytes, serum CO2, BUN, etc.) all of which showed normal results.  Hence, no anemia, and no evidence of kidney disease or metabolic disease associated with acidosis.

What is FTT, how is it diagnosed, and how is it treated?

The best definition I have yet seen of FTT was written by Cindy Christian and Nathan Blum in the textbook, Nelson Essentials of Pediatrics, 5th Edition (2006), Chapter 21, (Failure to thrive).  The authors wrote the following: “Failure to thrive (FTT) is a term given to malnourished infants and young children who fail to meet expected standards of growth.”  The authors went on to say that that the term FTT most often describes malnutrition related to environmental or psychosocial causes but that most children with FTT also have organic contributors.  The list of possible organic contributors is a long one and includes most every body system (e.g., genetic/congenital/anatomic, gastrointestinal, metabolic,  neurologic, renal, and hematologic disorders, as well as infections.  Thus, FTT is not really a specific diagnosis of anything but rather, a descriptor of certain signs and symptoms with poor weight gain always the “centerpiece.”  It’s sort of like a diagnosis of “limp,” which could be caused by anything from a rock in one’s shoe, to a serious bone or joint disease.  Regardless, once a paient is diagnosed with FTT,  every effort must be made to determine a specific etiologic diagnosis so that proper treatment, if any can be given in timely fashion.

How to sort through the myriad of diagnostic possibilities?

Once a diagnosis of FTT is made, the next step is for some knowledgeable health professional (e.g., nurse practitioner, pediatrician, pediatric endocrinologist) to get a detailed medical history.  The history should include as much information as possible about previous height and weight measurements and  laboratory test results.  In addition, the history should include detailed information about the infant’s feeding history and details about the family social history in an effort to uncover any potential environmental/psychosocial factors.  Next, a comprehensive physical examination should be performed that includes a developmental assessment. Well done medical histories and physical examinations are always “just what the doctor ordered” in any patient encounter, and in patients with FTT,  they are critically important.

The next step: developing a differential diagnosis

Armed with information from the medical history and physical examination, one can begin to develop a plan of action.  I usually start by asking myself 3 questions.  The first is whether, based on all the information available, I am reasonably confident the patient is normal and that the “poor” weight gain is/was a variant of normal and that no studies or treatment is needed.  Being reasonably confident is not the same thing as being 100% confident, and generally, such a patient should be seen for a follow-up clinic visit in the next 1-2 months.  The second question is whether I am reasonably confident the patient has a specific medical disorder that can explain the poor weight gain.  For example, if the history and physical examination strongly suggest a gastrointestinal basis for the poor weight gain, such as celiac disease, the next steps in the evaluation process are straightforward.  The third question is the most difficult one to deal with and is whether I am unable to decide whether the patient likely  is either normal or has some (as yet unknown) environmental/psychosocial and/or organic process to explain the poor weight gain.  Unfortunately, in my experience, even after a detailed medical history and physical examination, the answer to this question is often “yes,” necessitating considerable detective work.

Is the FTT merely a variant of normal growth?

It should be obvious that to determine if the FTT is not really FTT but only a normal growth variant, requires an understanding of normal growth.  I have discussed this subject in some detail in earlier entries but I will review things a bit for those of you who do not wish to hunt down the appropriate entries (I can’t even remember which ones, but they can be found by checking out entries in the growth disorders category.   Principle #1: children generally follow both weight and height growth channels very closely; if a child is at 50% for height at age 2 years, he or she is very likely to still be at that percentile at age 8 or 9 years of age.  Many normal children do not have height and height at the same percentile; it can be perfectly normal to be at 50% for height and 10% for weight and vice versa (but less desirable for a number of reasons that we will not discuss here).    There are 2 important exceptions to this principle; first, during infancy, children often do not stay in their height and weight channels.  Infants who are genetically programmed to be bigger than their height percentile at birth would suggest (to be precise, in children we pediatricians and pediatric endocrinologists, generally carry out length rather than height measurements up until age 2-3 years of age), show acceleration in both height and weight from the beginning, reaching the growth channel they will follow by about 1 year of age; premies often take somewhat longer.  For infants who are programmed to follow lower height and or weight channels than their height and or weight at birth, first follow the birth channels for about 6 months and then, gradually slow their growth rates- we call it “lag-down,” until about 18-20 months of age, at which point they track “like glue.”  The second exception to principle 1 is puberty.  All bets are off as to the growth rate (both height and weight) at puberty.  Children who are “destined” to end up at lower or higher height and or weight percentiles as adults than they followed during childhood, will generally fulfill their destinies.  Remember the following: Scottie dogs generally have Scottie dogs and Great Danes generally have Great Danes.  That saying is actually principle #2.

Back to KS

Remember KS, the 16 month old we were discussing?  Her growth pattern could be merely normal lag-down but I doubt it, since lag-down usually affects both height and weight.  Earlier, I didn’t mention that at the time of the visit to the pediatrician, RS was concerned that perhaps, KS was not getting adequate calories from the breast feeding alone.  KS decided to taper off the breast feeds and add table foods.  I got a follow-up from KS just the other day.  The family returned to the Netherlands, went to the clinic where the diagnosis of FTT was confirmed by a nurse practitioner, and an appointment was set up with a pediatrician; in the Netherlands, the primary care providers are often nurse practitioners.  But, RS told me that since decreasing the breast feeding and adding table foods ad lib, KS had been gaining weight like crazy and had progressed substantially with her development. So, in this instance it looks like the problem was inadequate calories and maybe a bit of vitamin D deficiency?  I am just speculating about the vitamin D deficiency but given that KS had not received any vitamin D supplementation and had been exclusively breast-fed, that’s a good possibility- vitamin D deficiency could explain the poor muscle tone and slow development.  The primary health care provider felt the problem was likely a nutritional one because of the much lower weight than height percentile and was betting on celiac disease or something like that (a reasonable hypothesis).  Anyway, we will need to wait until RS gives me another follow-up to find out if the problem in this case was more or less an environmental/psychosocial one rather than a systemic disorder.  I promise to let you know.  Finally, please do not infer from my entry that I am not a fan of breast feeding.  I think breast feeding is the way to go but that occasionally, problems do arise.  That’s why infants and children need regular check-ups by health care professionals who know all about monitoring growth (and breast feeding).  I suspect that for KS, part of the problem was related to the discontinuity in medical care because of the family travels between the U.S. and the Netherlands.  I am hoping things will turn out well.


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