Naoaki Hori

Microcephalic osteodysplastic primordial short stature type II with cafe‐au‐lait spots and moyamoya disease

Microcephalic osteodysplastic primordial ‘‘dwarfism’’ type 2 (MOPD2, MIM210720) is a severe intrauterine and postnatal growth retardation syndrome associated with craniofacial dysmorphism resembling that of Seckel syndrome and characteristic skeletal alterations [Majewski et al., 1982; Majewski and Goecke, 1998]. The presence of consanguinity in affected families implies an autosomal recessive inheritance [Al Gazali et al., 1995]. The MOPD gene is suspected to be on 1q21-q24, based on an MOPD patients with a deletion of the locus [Karasik et al., 1992]. We report here an affected boy associated with multiple cafe-au-lait spots and cerebral vasculopathy called ‘‘moyamoya disease’’. These previously undescribed associations may give another clue to the MOPD2 gene locus. The boy was the second child of healthy, nonconsanguineous parents. His older brother was healthy. The patient was vaginally delivered at 40 weeks of gestation after an unremarkable pregnancy. Birth weight was 1,470g ( 4.3 SD). Postnatal growth deficiency and microcephaly were significant. At age 4 8 12 years, his height was 67.3 cm ( 9.0 SD), weight 5,740 g ( 5.1 SD), and OFC 39.7 cm ( 6.8 SD). At seven years, height was 74.5 cm ( 9.0 SD), weight 6,490 g ( 4.4 SD), and OFC 41.0 cm ( 7.3 SD). The facial manifestations included receding forehead, downslanting palpebral fissures, prominent nose, low-set ears, and micrognathia. He was suspected as having MOPD2 at age one year on radiological grounds, including overtubulation of the tubular bones, metaphyseal cupping of the knee, and brachymesophalangy. He subsequently developed coxa vara and exaggerated metaphyseal cupping, warranted the diagnosis (Fig. 1a and b). Mental development was not retarded. Multiple cafe-au-lait spots that are ovoid, smooth-edged, and ranging in size from minute to 1.5 cm attracted attention at age three years. Chromosomes were normal. He developed left hemiparesis with generalized convulsion at age 4 5 12 years. Brain MR showed cerebral vasculopathy called ‘‘moyamoya’’ disease with cerebral infarction of the right cerebral hemisphere (Fig. 1c). At age 4 3 12 years, he showed propensity to fall and occasional mutism as symptoms of moyamoya disease, but did not have other neurological abnormalities. Under informed consent, we performed fluorescence in situ hybridization (FISH) analysis using DNA fragments flanking the 30 and 50 regions of the neurofibromatosis type 1 (NF1) gene. The probe for the 30 region was an extragenic marker spanning 208 kb distal to NF1, whereas the probe for the 50 region was a marker spanning 77 kb of both extra and intragenic regions of NF1 and including its exons 4 and 5. The study did not demonstrate a deletion of the regions (data not shown). The concurrence of MOPD2 with moyamoya disease and cafe-au-lait spots in the boy we described may be coincidental. However, taken it as a contiguous gene syndrome, an implication for the MOPD2 gene locus may be secured. We paid attention to 17q11.2 (the NF1 locus). Cafe-au-lait spots are essential manifestations of NF1. Cerebral vasculopathy is a rare association of NF1. The present boy did not show neurofibromas or Lisch nodules, which are characteristic of NF1. However, an unusual NF1 patient similar to our patient has *Correspondence to: Gen Nishimura, M.D., Department of Radiology, Nasu-Chuou Hospital, Shimoishigami 1453, Ohatawara-shi, Tochigi-ken 324-0036, Japan. E-mail: gen-n@pc4.so-net.ne.jp

Functional characterization of four novel PAX8 mutations causing congenital hypothyroidism: new evidence for haploinsufficiency as a disease mechanism

BACKGROUND Individuals carrying a heterozygous inactivating PAX8 mutation are affected by congenital hypothyroidism (CH), although heterozygous Pax8 knockout mice are not. It has remained unclear whether CH in PAX8 mutation carriers is caused by haploinsufficiency or a dominant negative mechanism. OBJECTIVE To report clinical and molecular findings of four novel PAX8 mutations, including one early-truncating frameshift mutation. SUBJECTS AND METHODS Four probands were CH patients. Two had family history of congenital or childhood hypothyroidism. Three probands were diagnosed in the frame of newborn screening for CH, while one had a negative result in screening but was diagnosed subsequently. Three had thyroid hypoplasia and one had a slightly small thyroid with low echogenicity. For these probands and their family members, we sequenced PAX8 using a standard PCR-based method. Pathogenicity of identified mutations was verified in vitro. RESULTS We found four novel heterozygous PAX8 mutations in the four probands: L16P, F20S, D46SfsX24, and R133Q. Family studies showed four additional mutation carriers, who were confirmed to have high serum TSH levels. Expression experiments revealed that three mutations (L16P, F20S, and R133Q) had defects in target DNA binding, while D46fs had protein instability that was rescued by the proteasome inhibitor MG132. All four mutations had reduced transactivation on the thyroglobulin promoter, supporting that they were inactivating mutations. CONCLUSION D46fs is the first PAX8 mutation with confirmed protein instability. Our clinical and in vitro findings together suggest that pure PAX8 haploinsufficiency can cause CH in humans.

Heterozygous C-propeptide mutations in COL1A1: Osteogenesis imperfecta type IIC and dense bone variant†‡

Osteogenesis imperfecta type IIC (OI IIC) is a rare variant of lethal OI that has been considered to be an autosomal recessive trait. Twisted, slender long bones with dense metaphyseal margins and normal vertebral bodies in OI IIC contrast with crumpled, thick long bones and multiple vertebral compression fractures in OI IIA. Here, we report on two sporadic patients with classical OI IIC and a pair of siblings, with features of OI IIC but less distortion of the tubular bones (OI dense bone variant). One case with OI IIC and the sibs had novel heterozygous mutations in the C‐propeptide region of COL1A1, while the second patient with clear‐cut OI IIC had no mutation in this region. Histological examination in the two sporadic cases showed a network of broad, interconnected cartilaginous trabeculae with thin osseous seams in the metaphyses. These changes differed from the narrow and short metaphyseal trabeculae found in other lethal or severe cases of OI. Our experience sheds light on the genetics and etiology of OI IIC and on its phenotypic spectrum.

Hyperinsulinemic hypoglycemia in a newborn infant with trisomy 13.

Trisomy 13 is the third most common trisomic disorder in human livebirths. The prevalence is about 1 in 5,000 births with high infant mortality. We describe a newborn infant with trisomy 13, who developed hyperinsulinemic hypoglycemia treated with diazoxide. The Japanese boy was the third child of a 34-year-old mother and a 34-year-old father. He was born by Cesarian section at 35 weeks of gestation due to late deceleration on non-stress test. His birth weight was 2,048 g (<10th centile), length 46.5 cm (10–50th centile), and OFC 31.0 cm (50–90th centile). Apgar scores were 1 and 2 at 1 and 5 min, respectively. Physical examination showed the following findings: frontal bossing, blepharophimosis, corneal clouding, right low-set ear, hypoplastic right earlobe, thin upper lip, hypoplastic philtrum, systolic heart murmur, overlapping fingers, posterior heel prominence, scrotalization of penis, and bilateral unpalpable testes. Chromosome analysis showed a 47,XY,þ13 karyotype. Blood glucose level at birth was 65 mg/dl. After birth (1 hr), his general activity was getting poor with blood glucose level of <40 mg/dl. As twice injections of 2 ml/kg of 20% glucose failed to increase his blood glucose level, continuous glucose infusion was introduced with the 5.0 mg/kg/min infusion rate. In total, 23 mg/kg/min of glucose infusion rate was needed to keep a blood glucose level of 80–90 mg/dl. On the 11th day, hypoglycemia (23 mg/dl blood glucose) was induced when the glucose infusion rate was decreased to 12 mg/kg/min. At that time, serum immunoreactive insulin level (24 IU/ml) was high (normal value, 2–10 IU/ml) together with relatively low free fatty acid (0.33 mEq/L; normal, 0.30–1.00 mEq/L) and low total ketone bodies (15 mmol/L; normal value, 26–122 mmol/L). Diazoxide (10 mg/kg/day) was administered since the 12th day and the glucose infusion rate was gradually decreased. On the 27th day, intravenous glucose infusion was discontinued without hypoglycemia. Judging from all these findings, the diagnosis of hyperinsulinemic hypoglycemia was convincing. It is plausible that hyperinsulinemic hypoglycemia is one of clinical manifestations of trisomy 13, although the possibility of an incidental complication cannot be ruled out. A review of the literature of trisomy 13 revealed two cases of hyperinsulinemic hypoglycemia. A female infant with mosaic trisomy 13 reported by Smith and Giacoia [1985] became very jittery with unmeasurable blood glucose 12 hr after birth, and when blood glucose level was 32 and 26 mg/dl, serum immunreactive insulin level became high, being 41 and 31 IU/ml, respectively. A very high glucose infusion rate (22 mg/kg/min) was also required in this patient to keep normoglycemia for the first 19 days. The other case was a female infant with trisomy 13 reported by Bellaton et al. [2002], developed hypoglycemia (blood glucose lavel, 12 mg/dl) without ketonuria immediately after birth and needed a very high glucose infusion rate (22 mg/ kg/min) to keep normoglycemia. In all these three cases, symptomatic hypoglycemia was evident within 12 hr after birth. The pathogenesis of hyperinsulinemic hypoglycemia in trisomy 13 remains unknown. Overdosage of certain gene(s) may lead to hyperinsulinism. Such candidate genes include the insulin promoter factor-1 gene (IPF1) [MIM 600733] located at 13q12.2, which binds the specific sequence within the promoter region of the insulin gene and activates its transcription [Ohlsson et al., 1993], and the caudal-type homeo box transcription factor 2 gene (CDX2) [MIM 600297] located at 13q12.3, encoding a homeodomein protein that binds an A/T-rich sequence in the insulin promoter and stimulates its transcription [German et al., 1992]. In view of the complexity of hyperinsulinemic hypoglycemia, its onset is likely determined by polygenes. This may explain why most patients with trisomy 13 do not develop symptomatic hyperinsulinemic hypoglycemia. Ductuloinsular complexes (incorporation of ducts into islets of Langerhans or the close association of endocrine cells with small knots of ductules) have been described in the pancreatic pathology in some patients with trisomy 13, which was interpreted as nesidioblastosis [Hashida et al., 1983; Moerman et al., 1988]. Nesidioblastosis has long been considered as the original lesion for the diffuse form of hyperinsulinism, although it is not specific.

A novel mutation in the C-propeptide of COL2A1 causes atypical spondyloepiphyseal dysplasia congenita

Spondyloepiphyseal dysplasia congenita (SEDC, OMIM #183900) is one of the type II collagenopathies caused by a heterozygous mutation in the COL2A1 gene. Although typical SEDC shows delay of pubic bone ossification on radiographs, atypical SEDC exists without this finding. We identified an atypical SEDC patient with a novel missense mutation in the C-propeptide region of COL2A1. This case suggests that a COL2A1 C-propeptide mutation can cause atypical SEDC.

A novel mutation of the THRB gene in a Japanese family with resistance to thyroid hormone.

Resistance to thyroid hormone (RTH; OMIM 190160) is an inherited syndrome of reduced sensitivity to thyroid hormone. RTH, in majority, is caused by monoallelic inactivating mutation of THRB, which encodes the thyroid hormone receptor β (TRβ) (1). RTH is endocrinologically characterized by high serum thyroid hormones together with inappropriately normal TSH. The severity of hormonal resistance varies among different tissues in an affected individual, due to differences in the relative expression of TRβ and thyroid hormone receptor alpha (TRα) in different tissues (2). To date, more than 100 THRB mutations have been reported among RTH patients. Most mutations are located in the ligand-binding domain of TR. They interfere with the function of the normal TR because of their dominant negative effect (1). We report a novel mutation of the THRB gene in a family with RTH.