Having spinal muscular atrophy (SMA) may increase a person's risk of developing certain types of cancer. However, cases of SMA are so rare, so researchers have had difficultly systematically studying this connection in a laboratory and clinical setting.

SMA is a neuromuscular disease in which genetic mutations cause muscle weakness due to nerve loss in the spinal cord. If an individual has SMA and cancer, they may have to adjust their treatment plan to manage both conditions. Many types of cancer have been associated with different types of SMA in several important case studies.

Cancer of the Central Nervous System

SMA has been linked to cancer of the central nervous system (CNS). The CNS is composed of the brain and spinal cord. Specifically, SMA has been shown in research literature to be linked to ependymomas, which are tumors of the CNS.

Ependymomas can affect children and adults. There are three types, or grades, of ependymomas. (The numbers for these grades are sometimes written in Roman numerals, e.g., grade II instead of grade 2.) Grade 1 ependymomas are low-grade tumors that grow slowly, usually in the spine. A grade 2 ependymoma is another type of low-grade tumor that can occur either in the brain or spinal cord. Grade 3 ependymomas, on the other hand, are malignant, fast-growing tumors. This type most commonly occurs in the brain, although they have also been found in the spinal cord.

One study reports the co-occurrence of ependymoma-associated cancers in a 33-year-old woman with SMA type 4. This type of SMA usually begins during adulthood.

Cancer of the Adrenal Glands

Researchers have noted a link between SMA and cancer in the context of neuroblastoma. Neuroblastoma is a type of cancer that forms either in or around the adrenal glands. The adrenal glands, which sit on top of the kidneys, produce important chemicals and hormones such as adrenaline (also known as epinephrine).

Neuroblastoma typically occurs during childhood and is rarely seen in older individuals. Sometimes, neuroblastoma tumors disappear on their own, and sometimes they require extensive treatment.

One clinical research team has noted that SMA and neuroblastoma can occur within the same family. In a case report, researchers observed that a child with SMA type 1 had a sibling with neuroblastoma. The sibling had tumors in the anterior horn of their spine, suggesting they may also carry a survival motor neuron type 1 (SMN1) mutation. These observations suggest a genetic connection between SMN1 gene abnormalities and tumor risk. Importantly, this study doesn’t suggest an isolated incident. Another case study observed the presence of SMA type 1 and neuroblastoma abdominal tumors in the same child, a 4-month-old infant male.

Cancer of Muscle Tissue

Rhabdomyosarcoma is another type of cancer linked to SMA. A sarcoma is a type of cancer that develops in connective tissues such as muscles, fat, bones, the linings of joints, or blood vessels. Rhabdomyosarcoma is a type of sarcoma that specifically occurs in skeletal muscles. Alveolar rhabdomyosarcoma in particular has been linked to SMA. Alveolar rhabdomyosarcoma occurs in large muscles, usually of the trunk, arms, or legs.

One study reports two cases of individuals with infantile SMA types 2 and 3a who developed alveolar rhabdomyosarcoma at ages 15 and 19, respectively. These two individuals were not related and represent two distinct examples of comorbid cancer and SMA. The researchers who conducted this study think that mutations in the SMN1 gene may be associated with benign tumors becoming malignant (or cancerous).

What’s the Connection?

This connection between SMA and certain types of cancer may be explained by genetics, although further research is necessary. Clinical trials are needed to explore this relationship and better learn how to treat both conditions. Members of mySMAteam have sometimes reported the occurrence of cancer alongside their diagnosis of SMA. For instance, one member with SMA type 3 was recently diagnosed with bone cancer. Another member has an extremely rare form of blood cancer but does not believe it is associated with her adult-onset SMA diagnosis.

Although there may be a connection between SMA, SMN protein, and cancer, more research is needed.

Building a Community

The social network mySMAteam is for people with spinal muscular atrophy. On mySMAteam, members come together to ask questions, share advice and experiences, and make connections with people around the world who understand life with SMA.

Have you experienced cancer with SMA? Share your experience in the comments below, or start a conversation by posting on mySMAteam.