TNNI3 and cutaneous mastocytosis: To date, 14 out of the 24 critical patients (58.3%) deceased: seven (50%) were affected by an inborn error of metabolism, two (14.3%) by a severe form of Rasopathy, one (7.1%) by a sarcomeric CM due to TNNI3 biallelic variants, and four (28.6%; two suspected syndromic CMs and two suspected inborn error of metabolism) remained undiagnosed.