This Rare Immune Disorder Has Killed Two Out of Three Moroccan Patients

The disease has a complex name: major histocompatibility complex class II deficiency, or MHC-II deficiency. This genetic abnormality prevents the immune system from responding properly to infections and exposes patients, from their first months of life, to potentially fatal complications.

Moroccan researchers studied the records of 54 patients from 47 families who were diagnosed between January 1998 and December 2024. All had been treated at the national reference center for primary immunodeficiencies at Ibn Rochd University Hospital in Casablanca.

The results of this cohort, one of the largest ever devoted to the disease in a single country, were published on August 24, 2026, by the scientific journal Frontiers in Immunology.

The findings are particularly serious: 36 of the 54 patients died, representing 66.7% of the cohort. Fifteen were still alive at the last follow-up, and three others were lost to follow-up. These results do not constitute a mortality rate applicable to all Moroccan patients, but describe the patients identified and followed by the center over 26 years.

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The first symptoms appeared at a median age of six months, but the diagnosis was not made until 19 months. The children therefore spent an average of thirteen months without the exact cause of their infections being identified.

Respiratory complications affected more than 96% of patients, and nearly three-quarters had suffered from pneumonia. The same proportion presented growth retardation. Chronic diarrhea, skin infections, candidiasis, ear infections and autoimmune complications were also frequent.

Only eight patients received a transplant

Hematopoietic stem cell transplantation is the only treatment capable of curing the disease. Yet only eight of the 54 patients studied, or 14.8%, were able to undergo it. Five were still alive at the last follow-up, aged between 10 and 24 years.

The other three died after severe infections. The time between diagnosis and the first transplant reached a median of 37.5 months among the records containing sufficient information. However, infections and lesions already present at the time of the procedure reduce the chances of success.

Outside transplantation, patients notably received intravenous immunoglobulins and preventive antibiotics. These treatments can limit infections, but do not correct the genetic abnormality.

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Genetic analysis revealed another distinctive feature. Of the 35 patients tested, 34 had the same deletion of the RFXANK gene, representing 97.1%. This so-called founder mutation is particularly common in North Africa.

Parental consanguinity was also reported in 47 of the 54 cases, or 87%. Since the disease is autosomal recessive, a child must receive a defective copy of the gene from each parent to be affected. The authors therefore recommend targeted molecular screening in at-risk families and enhanced genetic counseling.

In Morocco, around 1.5 million people are estimated to be living with one of the thousands of recorded rare diseases. Many endure a long diagnostic odyssey before receiving a diagnosis, even though early care can directly change their chances of survival.

The researchers believe that MHC-II deficiency is probably still underdiagnosed. They point to the absence of specific newborn screening, the still-insufficient recognition of early symptoms, and limited access to genetic testing and transplantation.

Mobilization around stem cell donors of Moroccan origin has recently progressed in Belgium, but the challenge remains considerable in Morocco. For the authors, identifying children earlier and facilitating their transplantation before severe infections develop are the two essential levers for reducing this mortality.