MIRAGE Syndrome

At a Glance

MIRAGE Syndrome is an acronym that stands for Myelodysplasia, Infection, growth Restriction, Adrenal hypoplasia, Genital phenotypes, and Enteropathy. Patients typically present with 5 or 6 of these clinical features. It is a syndromic form of life-threating congenital adrenal hypoplasia with extra-adrenal features. Most patients die before the age of 2 years.

Synonym

Myelodysplasia, Infection, Growth Restriction, Adrenal Hypoplasia, Genital Phenotypes, Enteropathy Syndrome.

History

MIRAGE Syndrome was first proposed by Narumi et al in 2016 to classify a form of syndromic adrenal hypoplasia with the constellation of myelodysplasia, infection, restriction of growth, adrenal hypoplasia, genital phenotypes, and enteropathy in patients with mutations of their SAMD9 proteins.

Classification

Syndromic congenital adrenal hypoplasia.

Incidence

A newly described syndrome, the exact incidence is unknown. To date, less than 25 patients with the syndrome have been reported. The vast majority of those cases involved patients who were Japanese males.

Genetic inheritance

MIRAGE Syndrome is inherited in an autosomal dominant fashion. Due to the high mortality rate, most incidences arise from heterozygous de novo mutations. However, germline mosaicism can occur. In addition to mutations in SAMD9 proteins, some patients may develop monosomy 7 Myelodysplastic Syndrome (MDS).

Pathophysiology

The exact pathophysiologic mechanism for this syndrome has yet to be determined. SAMD9 is an endosome facilitator protein that plays a role in growth factor signal transduction by meditated downregulation. Mutations to SAMD9 excessively activate intrinsic growth-restriction function resulting in severe prenatal and postnatal growth restriction. Development of monosomy 7 MDS in some patients with MIRAGE Syndrome occurs by “adaption-by-aneuploidy.” It is presumed the loss of chromosome 7 in some patients was an adaptation to the severe growth and restricting environment. These mutations result in the abnormal structural development (adrenal hypoplasia, growth restriction, thymus hypoplasia, underdeveloped genitals, myelodysplasia) and immunocompromised state seen in these patients. The majority of the patients reported with this syndrome have died from invasive infection.

Diagnosis

Diagnosis of MIRAGE Syndrome is confirmed by exome sequencing for SAMD9 mutations. Known variants include p.Arg459Gln, p.Asp769Asn, p.Arg1293Trp, p.Asn834Tyr, p.Glu974Lys, p.Ala1195Val, p.Pro1280Leu, and p.Gln1286Lys.

Clinical aspects

Common features of MIRAGE Syndrome include preterm delivery, intrauterine growth restriction (IUGR), adrenal insufficiency, underdeveloped genitals, thrombocytopenia, anemia, infection/sepsis, respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), diarrhea with colonic dilatation, and occasional changes to chromosome 7 resulting in MDS. Effects on intellectual development are variable. These patients may present for gastrointestinal and/or genitourinary procedures in early infancy.

Precautions before anesthesia

Patients with MIRAGE Syndrome are critically ill requiring intensive care immediately after birth. ...