Identifying DNA cousins can help with more than just finding common ancestors

For Em, Katie Bug, and EG...



Most of us think finding cousins during genealogy research is the best thing ever. I did and still do. But what if we can identify cousins and discover we have the same rare disease/disorder? Wouldn't that be even better?


A group of cousins and I collaborated on a project for six years, and, we discovered that some of us share a rare disease called Malignant Hyperthermia (MH) and more common non-alcoholic liver disease.


"Malignant Hyperthermia (MH) is a severe reaction to certain gases used during anesthesia and/or a muscle relaxant used to temporarily paralyze a person during surgery. Signs and symptoms of MH include marked hyperthermia, a rapid heart rate, rapid breathing, acidosis, muscle rigidity, and breakdown of muscle tissue (rhabdomyolysis). Without prompt treatment, MH can be life-threatening. People who are at increased risk for this reaction are said to have MH susceptibility. Susceptibility to MH may be caused by mutations in any of several genes and is inherited in an autosomal dominant manner. People with certain inherited muscle diseases (e.g., central core disease and multiminicore disease) also have MH susceptibility (https://rarediseases.info.nih.gov/diseases/6964/malignant-hyperthermia).


"While malignant hyperthermia itself is not inherited, malignant hyperthermia susceptibility (MHS) is inherited in an autosomal dominant manner. This means that having a mutation in only one copy of the responsible gene is enough to make someone susceptible to having malignant hyperthermia."(https://rarediseases.info.nih.gov/diseases/6964/malignant-hyperthermia/cases/46395)


I've known I've had an allergy to general anesthesia since after my youngest son was born when a mid 1980s biopsy indicated I had some abnormal cell growth and the situation needed to be addressed with surgery. The allergy to anesthesia wasn't diagnosed then as MH. The doctor told me I had a problem with the anesthesia but not in a way that made me concerned.


In 1997 I had to have another surgery. My doctor was aware I had some sort of problem with inhaled anesthesia, so to be safe he made notes to be sure the anesthesiologist checked my past records at the same hospital. Even though we both had a discussion about the unidentified problem with the anesthesiologist, he failed to check my hospital records. He was young, green behind the ears, and I've often wondered about the lesson he learned from my experience. During this surgery the same anesthesia problem happened. The surgery was stopped. In recovery, I heard the nurse calling my name, but I couldn't wake up. She slapped me hard across the face, but I still couldn't wake, and I heard her yell for someone to find the doctor.


Later in my room, my husband and I were having a discussion and I began to feel strange. The only way to describe the feeling is that I felt as if someone had begun squeezing a tube of toothpaste in my lower chest and was rolling the tube up, removing more breath with each squeeze. I tried to tell my husband there was a problem but I didn't have enough breath to speak. I began gasping for air, and he got out of the chair, came to me, and pounded the call button for the nurse. He later said I had turned blue when he called.


I coded. When I regained consciousness, I was on oxygen, connected to a defibrillator, an EKG, and tubes. The doctor was rubbing my calf. He thought I had an embolism. The young anesthesiologist was there, standing behind the doctor who was screaming and cursing at him. I stayed in ICU for 3 days until they could flush my system of the anesthesia, and I was fine. The doctor made sure I understood that other medical professionals who treated me should be told that I had an allergy to general anesthesia and that I had premature ventricular contractions (PVCs) and coded with these inhaled anesthesia meds.


My MH diagnosis was not made until last year by an anesthesiologist. I have not been genetically tested for MH. I developed NASH several years ago - non-alcoholic fatty liver disease - that has progressed to end stage non-alcoholic Cirrhosis of the Liver and have needed several associated surgeries in an effort to prevent life-threatening rupture of esophageal varices.


Associated MH genes are along chromosomes 1, possibly 17, and 19 (https://pubmed.ncbi.nlm.nih.gov/9508059/) and (https://rarediseases.org/rare-diseases/malignant-hyperthermia/). In 50% of the cases studied in multiple studies, the primary location for MH was caused from a mutation in gene 19q13.1 along chromosome 19 (https://rarediseases.org/rare-diseases/malignant-hyperthermia/). In 1%, the mutation is the "CACNA1S gene located on chromosome 1 (1q32)" (https://rarediseases.org/rare-diseases/malignant-hyperthermia/).


Glenna, one of my Morris & Pearce cousins questioned me about my allergy early on and told me about her brother RJN who had genetically tested positive for MH.


A large group of cousins along my maternal line share MRCAs James Morris and Nancy Pearce, including Glenna and her brother RJN. You can read the case study here. Some of these cousins have non-alcoholic liver problems and MH. I'm one of the farthest removed from these ancestors, so I don't share very much DNA with them, but loads of these cousins who share the Morris & Pearce line do indeed either share DNA or share overlapping segments along chromosomes 1, 17, and 19.


Allen Harris, my maternal first cousin (who also shares the Morris & Pearce ancestors), and I have overlapping segments of DNA along all three chromosomes with several other Morris & Pearce cousins.


On chromosome 19 our overlapping DNA segment with the genetically tested and positive MH cousin RJN begins at 28,079,145 and ends at 40,533,746. Below are images of overlapping DNA chromosome 19 segment (not to scale) between my maternal 1C Allen, RJN (confirmed genetic MH), and me.



You can view the chromosomal locus of the MH gene here, here, and here.


It's important to remember: Identifying DNA cousins using Genetic Genealogy can be helpful not only in identifying common ancestors but also the identification of shared diseases and those prevalent in certain lineages.


Thank you to all my Morris & Pearce cousins who DNA tested for me and who have shared health information. (https://www.morrispearce.com)


I understand little about these MH genes, so let me emphasize: This shared and/or overlapping DNA among my DNA cousins and me on these chromosomes might not be meaningful, but it is curious and interesting to me. I'm in the process of trying to better understand them.


DISCLAIMER: I am not a medical professional and I am not offering medical diagnoses or advice.




This is a series of stories I'm writing, because my older granddaughters gave me a journal years ago, and I've neglected writing in it. Recently I asked the oldest Emily if I should just write about the good. She said they want it all - the good, the bad, and the ugly. This blog will become that neglected journal.




66 views