Nevoid Basal Cell Carcinoma Syndrome (NBCCS)
What is nevoid basal cell carcinoma syndrome?
Nevoid basal cell carcinoma syndrome (NBCCS) is a rare, genetic condition that is characterized by various developmental disabilities and a predisposition to cancers, such as basal cell carcinoma.
Medical professionals are unsure as to the actual incidence of NBCCS, but they estimate it to be around one of every 30,000 people. This number could be higher, however, as many causes could go misdiagnosed and undiagnosed.
What are the symptoms of nevoid basal cell carcinoma syndrome?
Symptoms vary between affected individuals, as different parts of the body can be impacted and severity ranges.
A common symptom is the development of basal cell carcinoma, a form of skin cancer. Tiny spots that could be flesh-colored, brown, or orange will appear, and they can bleed or ulcerate. They most commonly appear on the face, chest, back, and nape of the neck.
Other tumors, such as keratocystic odontogenic tumors, appear as well. They tend to form in the jaw bones, causing swelling, pain, fractures in the teeth, loose teeth, or displaced teeth. In rare cases, affected individuals have reported medulloblastoma as well. Fibromas may also appear, along with cysts and polyps.
Other common symptoms include:
- Small pits on the palms of the hands and soles of the feet
- Being tall for an age group
- Distinctive facial features
- Rapid eye movements
- Crossed eyes
- Skeletal abnormalities, such as scoliosis or fused ribs
- Intellectual disability
- Minor kidney abnormalities
- Hardening of the skin
What causes nevoid basal cell carcinoma syndrome?
The majority of cases are caused by a mutated PTCH1 gene, which is a tumor suppressor gene. It is inherited in an autosomal dominant pattern, but medical professionals look at it as a “two-hit” gene. This means that only one mutated copy needs to be inherited to result in the majority of symptoms, but both copies must be abnormal in order for an individual to develop cancer.
This can also appear as a sporadic mutation. In fact, 35-50% of cases are new mutations.
How is nevoid basal cell carcinoma syndrome diagnosed?
Doctors diagnose NBCCS by either detecting the mutated gene or identifying the characteristic symptoms. They have a list of criteria, and patients must meet enough of the criteria to be formally diagnosed. Major criteria includes:
- First degree relative with NBCCS
- Keratocystic odontogenic tumors
- Two or more pits on the palms of the hands or soles of the feet
- Calcification of the falx cerebri
- Multiple basal cell carcinomas or one case before the age of 20
They will also perform tests, such as an MRI, abdominal ultrasound, X-ray, echocardiogram, and ovarian ultrasound.
What are the treatments for nevoid basal cell carcinoma syndrome?
Treatment is symptomatic. Surgery to remove tumors is common, and doctors will decide further cancer treatment depending on various factors. Two FDA approved drugs are also treatment options: sonidegib and vismodegib.
To prevent basal cell carcinoma and other cancers, doctors recommend staying out of the sun, wearing sunscreen, and wearing clothes that provide sun protection.