[A case of rare hereditary Siddiqi syndrome with novel neuropsychiatric signs].

A fifth world case of autosomal recessive Siddiqi syndrome (SIDDIS) related to FITM2 gene is presented. In a consanguineous Lezgin (a Dagestan ethnicity) family, there were two affected brothers aged 28 yrs (proband, personally examined) and 32 yrs. Whole-exome sequencing followed by familial Sanger sequencing detected a novel FITM2 missence variant c.452A>G, p.Asp151Gly homozygous in both patients and heterozygous in parents and unaffected brother. SIDDIS typical features in the patients were physical and motor delay with neuropsychiatric regress, loss of speech and walking, early-onset progressive sensorineural deafness, cognitive deficiency, skin lesion. However, there was no dystonia, which is a characteristic SIDDIS feature, while at least the proband had spastic paraparesis not described in SIDDIS earlier. Another distinction was mental state: behavioral disorders in both patients, positive symptoms in the proband and severe cognitive impairment in the brother. The case expands our understanding of the clinical and molecular-genetic spectrum of SIDDIS.