Part One of "Tay-Sachs Diagnosis -- Why It's Not Just A Simple Blood Test" discussed the difficulty in diagnosing Tay-Sachs disease because the disease is so rare, its initial presenting symptoms can be caused by any number of common and rare conditions, and the inaccurate belief held by many in the medical and lay community that Tay-Sachs is still a predominantly Jewish disease.

To reiterate some points made in Part 1 of this 2-part series:

• Testing for Tay-Sachs and other genetic diseases should be considered in a non-Jewish child presenting with symptoms of low muscle tone and developmental delay.
• Tay-Sachs has NOT been eradicated in Jews.
• Tay-Sachs is found in all ethnic groups.
• Tay-Sachs is more common amongst Irish Americans, French Canadians, Louisiana Cajuns, and Ashkenazi Jews than the general population.

Most children affected by Tay-Sachs present with more than just the symptom of low muscle tone. Their parents just don't realize it, and so the other "symptoms" that these kids already manifest are not reported on a routine pediatrician visit. It is not the parents' fault. Up until 6 to 9 months of age, most Tay-Sachs affected babies have been keeping up with their peers. They are able to coo, are learning to roll over, and are smiling, babbling, crying, and eating solid foods.

So what are some of the "hidden symptoms" that parents may overlook at this early age? One is the exaggerated startle reflex. The startle, or Moro, reflex is a completely normal reflex in infants up to 4 to 5 months of age and it suggests a well-integrated central nervous system. Persistence of the Moro reflex beyond 4 to 5 months, however, is not normal and it suggests the infant has severe neurological defects.

Parents do not generally realize that their child is startling abnormally since they have been startling all their lives up to that point. If a 6-month-old baby startles after a loud noise, most parents are not thinking, "It must be his central nervous system malfunctioning." Most parents just assume their child is startled by loud noises. It is only after the diagnosis that they realize their child's startle response has been exaggerated all along.

Another hidden symptom is a decrease in eye contact. This is extremely subtle in most Tay-Sachs children at 6 to 9 months of age, but more obvious at 12 to 14 months. If this symptom is caught first, a general eye exam will reveal the telling "cherry red spot", which is a hallmark sign of lipid storage diseases, which include Tay-Sachs, Sandhoff, and Niemann-Pick disease. Children with Tay-Sachs lose their once normal vision and are essentially blind by the age of 18 months.

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A third hidden symptom is the unexpected transition from "average" developmental rates to "delayed" developmental milestones. The Tay-Sachs child starts to lag behind their same-aged peers more noticeably. Again, it is subtle because these children are born essentially "normal", and at 6 months of age may still fall within normal range for most, if not all, developmental milestones. It is shortly thereafter that the gap quickly widens between the Tay-Sachs child and the typical child.

But this widening gap is different for each child and there are numerous causes of delayed development. By the time that simple blood test is done, the child may already be in the next stage of this dreaded disease: regression of developmental milestones.

The last "hidden" symptom that will be discussed is abnormal swallowing. Throughout the first year of life, Tay-Sachs kids are as hearty eaters as a typical child. Height and weight are generally normal and their enjoyment of food is obvious. A little cough or choke here and there is often overlooked, though it is likely a sign of gastro-esophageal reflux or the result of low tone in the swallowing muscles of the neck.

For some Tay-Sachs kids, this little cough or gag is just that for about the first 12 to 18 months of their lives. For other kids with Tay-Sachs, their weakened swallow results in aspiration of food or fluid; instead of the food going down the esophagus and into the stomach, the food goes into the trachea, or air pipe. If it cannot be coughed up, the food or fluid will go into the lungs. The lung will often respond with swelling and inflammation and this causes symptoms similar to asthma or reactive airway disease; wheezing is heard on lung exam, breathing rate increases, and oxygen saturation of the blood decreases. If severe, aspiration pneumonia can result, requiring antibiotics and aggressive respiratory care.

An undiagnosed 9 to 12 month old who is wheezing, may be given a relatively simple diagnosis of reactive airway disease. The parents may not realize their child has other symptoms. The astute physician will piece together the developmental delay, low muscle tone, and reactive airway symptoms and will start running tests and consulting specialists.

It is only then that a Tay-Sachs diagnosis is made with a simple blood test.

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