BBS7 and RIN2 variants cause Bardet Biedl syndrome and RIN2 syndrome respectively. We investigated a consanguineous family in which five individuals manifested different phenotypes. Whole-exome sequencing analyses of the individual with multiple phenotypes revealed homozygosity for novel pathogenic variants in his DNA sample; a frameshift variant in RIN2 (c.1938delT) and a splice-site variant in BBS7 (c.1677-1G > A). Other affected individuals were homozygous for a variant in only one of either gene and consequently manifested phenotypes respective to one disorder. Our work shows that exome sequencing of the most severely affected individual can help in the identification of pathogenic variants in more than one involved genes in a particular family.

RIN2 syndrome also known as MACS syndrome is a rare autosomal recessive connective tissue disorder caused by RIN2 mutations and is accompanied by following clinical features: macrocephaly, coarsening of facial features, downward slanting palpebral fissures, Puffy droopy eyelids, full everted lips, soft redundant skin especially in face, gum hypertrophy, irregular dentition, sparse scalp hair, skeletal problems, joint hypermobility and scoliosis. RIN2 gene encodes the RAS and RAB interactor 2 and biallelic mutations in this gene cause cell trafficking dysfunction. Here we reported the eleventh patient of RIN2 syndrome in a 4 yr-old boy, from Tehran, Iran as the youngest reported patient so far. Whole exome sequencing revealed a novel frameshift homozygous variant of NM_001242581.1: c.2251dup; p.(Leu751Profs*9) in RIN2 gene. In addition to the previously reported symptoms for the RIN2 syndrome, white matter abnormalities in his brain MRI were noticed. Our findings expand the clinical spectrum of MACS syndrome due to mutation in RIN2 gene.

Biallelic defects in the RIN2 gene, encoding the Ras and Rab interactor 2 protein, are associated with a rare autosomal recessive connective tissue disorder, with only nine patients from four independent families reported to date. The condition was initially termed MACS syndrome (macrocephaly, alopecia, cutis laxa, and scoliosis), based on the clinical features of the first identified family; however, with the expansion of the clinical phenotype in additional families, it was subsequently coined RIN2 syndrome. Hallmark features of this condition include dysmorphic facial features with striking, progressive facial coarsening, sparse hair, normal to enlarged occipitofrontal circumference, soft redundant and/or hyperextensible skin, and scoliosis. Patients with RIN2 syndrome present phenotypic overlap with other conditions, including EDS (especially the dermatosparaxis and kyphoscoliosis subtypes). Here, we describe a 10th patient, the first patient of Caucasian origin and the oldest reported patient so far, who harbors the previously identified homozygous RIN2 mutation c.1878dupC (p. (Ile627Hisfs*7)). Besides the hallmark features, this patient also presents problems not previously associated with RIN2 syndrome, including cervical vertebral fusion, mild hearing loss, and colonic fibrosis. We provide an overview of the clinical findings in all reported patients with RIN2 mutations and summarize some of the possible pathogenic mechanisms that may underlie this condition. © 2016 Wiley Periodicals, Inc.