First evidence of maternally inherited mosaicism in TGFBR1 and subtle primary myocardial changes in Loeys-Dietz syndrome: a case report

Loeys-Dietz syndrome (LDS) is a rare multisystemic disorder characterized by vascular and skeletal abnormalities, with considerable intra- and interfamilial variability.

We report the case of an 8-year-old male with clinical features of two distinct genetic disorders, namely LDS, manifesting in the first months by progressive aortic root dilatation, arterial tortuosity, bifid uvula, and inguinal hernias and oculocutaneous albinism (OCA) manifesting by white hair and skin that does not tan, nystagmus, reduced iris pigment with iris translucency, and reduced retinal pigment). We identified previously reported, homozygous mutations of TYR, c.1A > G (p.Met1Val) and heterozygous, missense mutation of TGFBR1, c.1460G > A (p.Arg487Gln). Family history revealed that his mother underwent multiple surgical repairs for recurrent hemorrhage originating from the buccal artery. Molecular studies confirmed a maternally inherited low grade TGFBR1 mutation somatic mosaicism (18% in peripheral blood leukocytes, 18% in buccal cells and 10% in hair root cells). Maternal cardiac investigations revealed peculiar cardiovascular features: mild tortuosity at the aortic arch, dilatation of the proximal abdominal aorta, multiple deep left ventricular myocardial crypts, and dysplastic mitral valve. TGFBR2 germline mosaicism has been described in three fathers of children carrying TGFBR2 mutations but, to the best of our knowledge, no case of maternally inherited TGFBR1 mutation mosaicism has been reported so far.

This case report suggests that individuals with somatic mosaicism might be at risk for mild and unusual forms of LDS but germline mosaicism can lead to full blown picture of the disease in offspring.