Table 2 Differential diagnosis of Smith–Magenis syndrome

9q34 deletion syndrome

#610253, ^*607001

Mental retardation, brachycephaly, flat face, midface hypoplasia, tented upper lip, short nose, hypertelorism, synophrys, prognathism, hypotonia, cardiac anomalies, seizures, hearing loss, sleep disturbance, obsessive-compulsive disorders, and stereotypic movements

EHMT1

Down syndrome (Trisomy 21)

#190685, ^*602917, ^*605296, ^*605298, ^*604829

Mental retardation, hypotonia, short stature, brachycephaly, epicanthic folds, upward slanting palpebral fissures, flat facies, congenital heart defects, Brushfield spots (iris), single palmar crease, brachydactyly, small and low-set ears, obstructive sleep apnea, and cardiac and endocrine problems

DSCR1, DSCR2, DSCR3, DSCR4

Williams syndrome (del(7)q11.23)

#194050, ^*130160, ^*601329, ^*603432, ^*604318, ^*601679

Mental retardation, characteristic ‘elfin’ facies, supravalvular aortic stenosis, hypercalcemia, prenatal growth retardation, short stature, lack of depth perception, and a friendly, loquacious personality

ELN, LIMK1, CYLN2, GTF2IRD1, GTF2I

Prader–Willi syndrome (paternal del(15)q11-q13)

#176270, ^*182279, ^*602117

Mental retardation, speech and motor delay, brachycephaly, almond-shaped eyes, down-turned mouth with thin upper lip, hypotonia, short stature, gait abnormalities, hyperphagia, genital hypoplasia, and self-injurious and obsessive-compulsive behaviors

SNRPN, Necdin

22q11.2 deletion syndrome (DiGeorge/velocardiofacial syndromes)

#188400, #192430, ^*602054

Congenital heart disease, velopharyngeal insufficiency, cognitive and motor delay, feeding difficulties, immune deficiency, hypocalcemia, hearing loss, and skeletal abnormalities

TBX1

Sotos syndrome

#117550, ^*606681

Mental retardation, hypotonia, cognitive and motor delay, feeding difficulties, tall stature, macrocephaly, malar flushing, frontotemporal hair sparsity, down-slanting palpebral fissures, seizures, scoliosis, and cardiac and renal anomalies

NSD1