Phenotype and genotype of index patient with ZBTB24 mutation. (A) Clinical signs at 8 years-of-age: protruding abdomen due to organomegaly in the otherwise underweight girl of short statue, facial dysmorphism (hypertelorism, epicanthal folds, flat nasal bridge, hypertelorism, slight ptosis, prominent forehead). Large teeth result from a fusion of first molar with the incisors. Fingers and toes showed clubbing. Failure to thrive evident in a percentile height-weight-curve. (B) Pseudo-Pelger-Huët anomaly of neutrophils (Diff-Quick staining, 100x, n = 400 cells, Student’s t-test, p < 0.0001). (C) Site of homozygous ZBTB24 mutation c.1222 T > G (protein domains: BTB, bric-a-bric, tramtrack, broad complex domain; AT hook, DNA-binding domain with a preference for A/T rich regions, Zinc finger C2H2). (D) Electropherogram traces in patient and heterozygous parents (NM_014797) indicating mutation confirmed by Sanger sequencing. Unaltered ZBTB24 mRNA levels and product size is depicted in Additional file 8: Figure S2. (E) Highly conserved amino acids affected by the inherited homozygous mutation (p.C408G). (F) Spontaneous undercondensation of constitutive heterochromatin of chromosomes 1q, 16q, and (to a lesser extent) 9q.