Severe combined immunodeficiency (SCID) is a type of primary immunodeficiency, meaning some of the necessary parts to build a functioning immune system are either missing or not working in the body. It is the result of genetic mutations that primarily affect the T cells, and often at least one other type of immune cell. (1) The diagnosis is considered a pediatric emergency. Babies born with SCID typically only have a few years to live without any type of medical intervention or treatment to address their weakened immune system. (2)
According to various medical journals, the first case of SCID found in humans was reported in 1950. The first molecular cause of SCID (adenosine deaminase deficiency or “ADA”) was identified in 1972. (3) Reported clinical cases revealed babies with SCID were at an increased risk for developing infections that had the potential to become fatal without a functioning immune system to fight it.
As someone born before the diagnostic measures and transformational treatments available today, I consider myself lucky to have even received a clinical diagnosis at only 2 years old. My parents relentlessly pursued over 40 doctors within those two years to be able to put a name to what was causing my symptoms and failure to thrive.
To parents reading this: I’m even luckier than I previously admitted. I was able to receive enzyme replacement therapy for SCID-ADA, which kept me alive until I took part in the first gene therapy trial in the world, at 4 years of age, in 1990, at the National Institutes of Health. I am forever indebted to my parents for being willing to take part in what was probably the most experimental and controversial clinical trial at the time, while still caring for two other kids with physical disabilities, and the doctors who chose to invest in rare disease research.
Within the past 30 years or so, particularly for X-linked and SCID-ADA, an enormous amount of progress has been made in attempting to identify, research and treat this rare syndrome. Currently, there are at least 13 different types of identified SCID, with various “unknown” types still being discovered. X-linked SCID (primarily affecting boys), is the most common form, representing about 40 percent of SCID cases. SCID-ADA is the second most prevalent type of SCID, identified in approximately 15 percent of cases. (4) (5)
The story of David Vetter, known as the “Bubble Boy” in the 70s and 80s, brought SCID to the forefront of the medical community and the world. Photos of him in his protective bubble, designed to act as a barrier between him and outside bacteria and germs, captivated the hearts and minds of all who followed his story. To SCID families, David is a hero and the epitome of strength and hope. Though his life was short-lived, his advocacy and help propelling research forward for SCID are etched in medical history forever. (6)
For those interested in SCID, here are five more facts you should know.
1. Better Screening Protocols Allow for Earlier and More Diagnoses
While SCID was previously thought to affect approximately one in 100,000 in the US. The advent and implementation of newborn screening have increased the prevalence to approximately one in 58,000 children diagnosed each year. (7) SCID cases are more frequently diagnosed in the Navajo, Amish and Mennonite communities. (8)
2. Symptoms Appear Very Early in Life
These include general failure to thrive, frequent ear and/or sinus infections, infections that don’t improve with medicine, persistent skin rashes and/or infections, diarrhea, and yeast infections. Babies or children may exhibit some or all of these symptoms, but severe infections, whether in the bloodstream or lungs, like pneumonia, are most common. (9)
3. Early Diagnosis Is Critical
Because of the high mortality rate associated with SCID if left untreated, interventions have been necessary to ensure babies are diagnosed as soon as possible. Enter in newborn screening, a life-saving measure for many rare diseases, especially those that progress quickly after birth. Through tremendous patient advocacy efforts over the past 10 years, all states within the US now implement newborn screening for SCID, meaning babies can be diagnosed at birth, and given a greater chance to thrive and receive treatment early. (10)
4. There Are Several Treatment Options
Once children are diagnosed, the available options for treatment include a hematopoietic stem cell transplantation (HSCT) with cells taken either from the bone marrow, peripheral or cord blood. Finding a matched donor can prove to be a significant obstacle for some families.
Another option, especially for those who are not able to find a matched donor, is gene therapy. This potential treatment has garnered a great deal of excitement and controversy in the news and the medical community. Within the past decade, many patients with SCID-ADA and X-linked SCID who have received the lentiviral gene therapy have thrived – with some being able to even receive full vaccinations and wean off supportive treatments.
Although the current form of gene therapy for SCID is often touted as a potential “cure,” it is important for families to continue with follow-up with their doctors and specialists, as the long-term effects of gene therapy are still unknown. Patients with SCID who have not found successful treatment with HSCT and/or gene therapy often will require supplemental therapies, like enzyme replacement (common for SCID-ADA), or immunoglobulin infusions. (11)
5. Research Has Made so Much Progress but There Is Still More to Be Made
There are no words to describe the gratitude for being born in a time where potential treatments are available for your particular rare disease, especially when only 5 percent of those diagnosed with a rare disease have an effective FDA-approved treatment on the market. (12)
It almost feels unimaginable to see life-changing treatments like gene therapy come full circle in my short 33 years of life. Still, as a patient advocate, I will always hesitate to use the word “cure” for treatments that are relatively new and still being perfected. While SCID families and patients are grateful for transformative therapies like gene therapy and HSCT, especially when the previous alternative was a shortened lifespan, we all need to continue to be diligent in our follow-up protocol with doctors, and keep an eye out for potential progression of the condition, should these treatments ever stop working.
Newborn screening campaigns, accessible HSCT treatment centers and centers for gene therapy across the globe are still needed – so every child, regardless of where they are born, has a fair chance at receiving a diagnosis and treatment, and living life to their fullest potential.