Kenny-Caffey syndrome in two sibs born to consanguineous parents: evidence for an autosomal recessive variant

Quantitative hypermorphic FAM111A alleles cause autosomal recessive Kenny-Caffey syndrome type 2 and osteocraniostenosis

Kenny-Caffey syndrome (KCS) is a rare genetic disorder characterized by extreme short stature, cortical thickening and medullary stenosis of tubular bones, facial dysmorphism, abnormal T cell function, and hypoparathyroidism. Biallelic loss-of-function variants in TBCE cause autosomal recessive type 1 KCS (KCS1). By contrast, heterozygous missense variants in a restricted region of the FAM111A gene have been identified in autosomal dominant type 2 KCS (KCS2) and a more severe lethal phenotype, osteocraniostenosis (OCS); these variants have recently been shown to confer a gain of function. In this study, we describe 2 unrelated children with KCS and OCS who were homozygous for different FAM111A variant alleles that result in replacement of the same residue, Tyr414 (c.1241A>G, p.Y414C and c.1240T>A, p.Y414N), in the mature FAM111A protein. Their heterozygous relatives are asymptomatic. Functional studies of recombinant FAM111AY414C demonstrated normal dimerization and a mild gain-of-function effect. This study provides evidence that both biallelic and monoallelic variants of FAM111A with varying degrees of activation can lead to dominant or recessive KCS2 and OCS.

Key Clinical and X-Ray Characteristics for the Diagnosis of Kenny-Caffey Syndrome Types 1 and 2

Introduction

Kenny-Caffey syndrome (KCS) is a rare syndrome characterized by short stature, hypoparathyroidism, eye abnormalities, and skeletal dysplasia. Two types of KCS result from pathogenic variants in the tubulin-specific chaperone E (TBCE) gene and the family with sequence similarity 111 member A (FAM111A) gene, respectively.

Case Presentation

In this study, we present 4 patients from three different families exhibiting facial dysmorphism, postnatal growth retardation, short stature, delayed bone age, cortical thickening and medullary stenosis of the bones, and hypoparathyroidism. Two of these cases were diagnosed with growth hormone (GH) deficiency and underwent GH therapy, highlighting the response to GH treatment in KCS. Three consanguineous cases of KCS type 1 possess a homozygous variant c.155_166del in the TBCE gene, and 1 patient with KCS type 2 has a de novo pathogenic variant c.1706G>A (p.Arg569His) in the FAM111 gene.

Conclusions

Our findings suggest that prenatal and postnatal growth failure is a prominent characteristic of this syndrome, with KCS types 1 and 2 showing overlapping features.

Further delineation of phenotype and genotype of Kenny-Caffey syndrome type 2 (phenotype and genotype of KCS type 2)

BACKGROUND

Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare inherited disorder characterized by proportionate short stature, skeletal defects, ocular and dental abnormalities, and transient hypocalcemia. It is caused by variants in FAM111A gene. Diagnosis of KCS2 can be challenging because of its similarities to other syndromes, the absence of clear hallmarks and the deficient number of genetically confirmed cases. Here, we aimed to further delineate and summarize the genotype and phenotype of KCS2, in order to get a better understanding of this rare disorder, and promote early diagnosis and intervention.

METHODS

We present clinical and genetic characteristics of eight newly affected individuals with KCS2 from six families, including one family with three individuals found to be a father-to-daughter transmission, adding to the limited literature. Furthermore, we performed a review of genetically confirmed KCS2 cases in PubMed, MEDLINE and CNKI databases.

RESULTS

There were six females and two males in our cohort. All the patients presented with short stature (100.0%). Clinical manifestations included ocular defects such as hypermetropia (5/8), dental problems such as defective dentition (3/8) and dental caries (3/8), skeletal and brain anomalies such as delayed closure of anterior fontanelle (6/8), cerebral calcification (3/8), cortical thickening (3/8) and medullary stenosis (4/8) of tubular bones. Endocrinologic abnormalities included hypoparathyroidism (5/8) and hypocalcemia (3/8). One male patient had micropenis and microorchidism. All cases harboured missense variants of FAM111A, and nucleotides c.1706 arose as a mutational hotspot, with seven individuals harbouring a c.1706G>A (p.Arg569His) variant, and one child harbouring a c.1531T>C (p.Tyr511His) variant. Literature review yielded a total of 46 patients from 20 papers. Data analysis showed that short stature, hypoparathyroidism and hypocalcemia, ocular and dental defects, skeletal features including cortical thickening and medullary stenosis of tubular bones, and seizures/spasms were present in more than 70% of the reported KCS2 cases.

CONCLUSION

We provide detailed characteristics of the largest KCS2 group in China and present the first genetically confirmed instance of father-to-daughter transmission of KCS2. Our study confirms that Arg569His is the hot spot variant and summarizes the typical phenotypes of KCS2, which would help early diagnosis and intervention.

Clinical and Molecular Diagnosis of Osteocraniostenosis in Fetuses and Newborns: Prenatal Ultrasound, Clinical, Radiological and Pathological Features

Osteocraniostenosis (OCS, OMIM #602361) is a severe, usually lethal condition characterized by gracile bones with thin diaphyses, a cloverleaf-shaped skull and splenic hypo/aplasia. The condition is caused by heterozygous mutations in the FAM111A gene and is allelic to the non-lethal, dominant disorder Kenny‐Caffey syndrome (KCS, OMIM #127000). Here we report two new cases of OCS, including one with a detailed pathological examination. We review the main diagnostic signs of OCS both before and after birth based on our observations and on the literature. We then review the current knowledge on the mutational spectrum of FAM111A associated with either OCS or KCS, including three novel variants, both from one of the OCS fetuses described here, and from further cases diagnosed at our centers. This report refines the previous knowledge on OCS and expands the mutational spectrum that results in either OCS or KCS.

Parathyroid hormone

Parathyroid hormone is an essential regulator of extracellular calcium and phosphate. PTH enhances calcium reabsorption while inhibiting phosphate reabsorption in the kidneys, increases the synthesis of 1,25-dihydroxyvitamin D, which then increases gastrointestinal absorption of calcium, and increases bone resorption to increase calcium and phosphate. Parathyroid disease can be an isolated endocrine disorder or part of a complex syndrome. Genetic mutations can account for diseases of parathyroid gland formulation, dysregulation of parathyroid hormone synthesis or secretion, and destruction of the parathyroid glands. Over the years, a number of different options are available for the treatment of different types of parathyroid disease. Therapeutic options include surgical removal of hypersecreting parathyroid tissue, administration of parathyroid hormone, vitamin D, activated vitamin D, calcium, phosphate binders, calcium-sensing receptor, and vitamin D receptor activators to name a few. The accurate assessment of parathyroid hormone also provides essential biochemical information to properly diagnose parathyroid disease. Currently available immunoassays may overestimate or underestimate bioactive parathyroid hormone because of interferences from truncated parathyroid hormone fragments, phosphorylation of parathyroid hormone, and oxidation of amino acids of parathyroid hormone.

Ophthalmologic Impairment and Intellectual Disability in a Girl Presenting Kenny-Caffey Syndrome Type 2

Kenny-Caffey syndrome (KCS) is a rare genetic condition characterized by growth retardation, bone abnormalities, and hypoparathyroidism. Herein, we report an unusual case of a 10-year-old girl with Kenny-Caffey syndrome type 2 (KCS2) presenting with vision impairment-suspected maculopathy and intellectual disability. Endocrine evaluation showed low calcium and high phosphorus plasma levels. Radiographic evaluation revealed short metacarpal bones and delayed bone age. Sequencing analysis showed a missense variant in FAM111A (R569H), unidentified in her parents. Better understanding of potential neurological and ophthalmological findings in KCS2 patients is important to improve quality of life of these patients as usually they exhibit long survival.

Genetic Disorders of Parathyroid Development and Function

Hypoparathyroidism is characterized by hypocalcemia and hyperphosphatemia and is due to insufficient levels of circulating parathyroid hormone. Hypoparathyroidism may be an isolated condition or a component of a complex syndrome. Although genetic disorders are not the most common cause of hypoparathyroidism, molecular analyses have identified a growing number of genes that when defective result in impaired formation of the parathyroid glands, disordered synthesis or secretion of parathyroid hormone, or postnatal destruction of the parathyroid glands.

Kenny Caffey syndrome with severe respiratory and gastrointestinal involvement: expanding the clinical phenotype

Kenny Caffey syndrome (KCS) is a rare syndrome reported almost exclusively in Middle Eastern populations. It is characterized by severe growth retardation-short stature, dysmorphic features, episodic hypocalcaemia, hypoparathyroidism, seizures, and medullary stenosis of long bones with thickened cortices. We report a 10-year-old boy with KCS with an unusually severe respiratory and gastrointestinal system involvement-features not previously described in the literature. He had severe psychomotor retardation and regressed developmentally from walking unaided to sitting with support. MRI brain showed bilateral hippocampal sclerosis, marked supra-tentorial volume loss and numerous calcifications. A 12 bp deletion of exon 2 of tubulin-specific chaperone E (TBCE) gene was identified and the diagnosis of KCS was confirmed. Hypercarbia following a sleep study warranted nocturnal continuous positive airway pressure (CPAP) when aged 6. When boy aged 8, persistent hypercarbia with increasing oxygen requirement and increased frequency and severity of lower respiratory tract infections led to progressive respiratory failure. He became fully dependent on non-invasive ventilation and by 9 years he had a tracheotomy and was established on long-term ventilation. He developed retching, vomiting and diarrhea. Chest CT showed changes consistent with chronic aspiration, but no interstitial pulmonary fibrosis. He died aged 10 from respiratory complications.

Kenny-Caffey syndrome type 1

Kenny-Caffey syndrome type 1 is a rare hereditary skeletal disorder. We present here a documented case of a 7-month-old girl with the characteristic symptoms of growth retardation, dysmorphic features, and hypoparathyroidism.

A recurrent de novo FAM111A mutation causes Kenny-Caffey syndrome type 2

Kenny-Caffey syndrome (KCS) is a rare dysmorphologic syndrome characterized by proportionate short stature, cortical thickening and medullary stenosis of tubular bones, delayed closure of anterior fontanelle, eye abnormalities, and hypoparathyroidism. The autosomal dominant form of KCS (KCS type 2 [KCS2]) is distinguished from the autosomal recessive form of KCS (KCS type 1 [KCS1]), which is caused by mutations of the tubulin-folding cofactor E (TBCE) gene, by the absence of mental retardation. In this study, we recruited four unrelated Japanese patients with typical sporadic KCS2, and performed exome sequencing in three patients and their parents to elucidate the molecular basis of KCS2. The possible candidate genes were explored by a de novo mutation detection method. A single gene, FAM111A (NM_001142519.1), was shared among three families. An identical missense mutation, R569H, was heterozygously detected in all three patients but not in the unaffected family members. This mutation was also found in an additional unrelated patient. These findings are in accordance with those of a recent independent report by a Swiss group that KCS2 is caused by a de novo mutation of FAM111A, and R569H is a hot spot mutation for KCS2. Although the function of FAM111A is not known, this study would provide evidence that FAM111A is a key molecule for normal bone development, height gain, and parathyroid hormone development and/or regulation.

Neurological manifestations in children with Sanjad-Sakati syndrome

Background:

Sanjad–Sakati syndrome (SSS), also known as hypoparathyroidism–mental retardation–dysmorphism syndrome, or HRD, is a rare disorder characterized by growth and developmental delay, and by mental retardation and dysmorphic features.

Objective:

The objective of this study was to clarify the clinical and neurological features of SSS.

Patients:

Twenty-four patients were included in the study. They were seen at two hospitals in Kuwait.

Methods:

This was a retrospective study of patients with SSS who attended the pediatric endocrinology, genetic, and neurology clinics in the Aladan and Alfarawanya hospitals in Kuwait from September 2007 to September 2012. Clinical and radiological data were obtained from each patient’s medical records.

Results:

All 24 patients had the characteristic dysmorphic features and laboratory findings of SSS. Consanguinity was reported in 75% of parents. Neurological manifestations in the form of microcephaly, developmental delay, mental retardation, and seizures were reported in all patients. Computerized tomography scans and/or magnetic resonance imaging showed evidence of intracranial calcifications in 29.2% of patients. Two patients showed a thin corpus callosum, and one patient showed intraventricular hemorrhaging.

Conclusion:

Patients with SSS display a variety of dysmorphic features and neurological manifestations, including microcephaly, mental retardation, intracranial calcification, and epilepsy.

Kenny-Caffey syndrome type 1 in an Egyptian girl

Kenny-Caffey syndrome type 1 (KCS1) (OMIM 244460) is a rare syndrome characterized by growth retardation, uniformly small slender long bones with medullary stenosis, thickened cortex of the long bones, hypocalcemia possibly with tetany at an early age and normal intelligence. The primary outcome of KCS1 is short stature. We present here an Egyptian girl aged 32 months with typical feature of KCS1.

Peripapillary choroidal neovascularization associated with kenny syndrome

PURPOSE

To report a case of Kenny-Caffey syndrome with peripapillary choroidal neovascularization.

METHODS

An observational case report with clinical findings demonstrated by wide-field retinal photographic and angiographic evaluation of a patient with Kenny-Caffey syndrome.

RESULTS

Wide-field retinal photography and fluorescein angiography showed characteristic findings seen in Kenny-Caffey syndrome (crowded optic nerves, retinal vascular tortuosity). In addition, the previously undocumented finding of peripapillary choroidal neovascularization is demonstrated.

CONCLUSION

The development of peripapillary choroidal neovascularization can occur in patients with Kenny-Caffey syndrome. The development of this finding may be secondary to abnormalities of the optic nerve inherent in this rare disorder.

HDR syndrome: a novel "de novo" mutation in GATA3 gene

Human GATA3 haploinsufficiency leads to HDR (hypoparathyroidism, deafness, and renal dysplasia) syndrome. The development of a specific subset of organs in which this transcription factor is expressed appears exquisitely sensitive to gene dosage. We report on a 14-year-old patient with symptomatic hypoparathyroidism, sensorineural bilateral deafness, unilateral renal dysplasia, bilateral palpebral ptosis, and horizontal nystagmus. Fundoscopy displayed symmetrical pseudopapilledema, and brain CT scan revealed basal ganglia calcifications. FISH analysis did not disclose any microdeletion in the 22q11.2 or 10p14 regions. GATA3 mutation analysis identified a heterozygous deletion of GG nucleotides at codon 36 and 37 (c.108_109delGG) in exon 2 causing a frameshift with a premature stop codon after a new 15-aminoacid sequence. Restriction endonuclease analysis performed in parents was negative. Our patient carries a novel "de novo" GATA3 mutation, providing further evidence that HDR syndrome is caused by haploinsufficiency of GATA3, which may be responsible for a complex neurologic picture besides the known triad.

Hypoparathyroidism-retardation-dysmorphism syndrome in a girl: A new variant not caused by aTBCEmutation-clinical report and review

Hypoparathyroidism-retardation-dysmorphism (HRD) or Sanjad-Sakati syndrome (SSS) (OMIM 241410) is a rare autosomal recessive (AR) inherited condition, characterized by congenital hypoparathyroidism (hypoPTH), retardation, seizures, and a typical facial dysmorphism, consisting of prominent forehead, deep-set eyes, and abnormal external ears. This disorder has been mapped to the long arm of chromosome 1 (1q42-q43) and mutations in the gene coding for tubulin-specific chaperone E (TBCE) have been identified as the cause of the disease. Mutations in the same gene were also reported in patients with AR Kenny-Caffey syndrome (KCS). We report on a 41/2-year-old girl with congenital hypoPTH, seizures, developmental delay, and a facial dysmorphism, compatible with HRD syndrome. Mutation analyses revealed no mutations in the TBCE gene. In addition, normal TBCE protein and alpha-tubulin immunostaining were observed in a lymphoblastoid line derived from the patient, excluding the TBCE gene as the causative gene of the syndrome in this patient. A de novo microduplication of probe RP11-262I1 on 4q35 in the proposita was detected by microarray analyses, but this could not be confirmed by additional studies. We review and discuss the clinical findings of our case and those of the other reported cases with SSS and AR KCS. We conclude that a second gene locus for this disorder seems probable and that 4q35 needs further evaluation as a candidate region.

Perinatal calcium metabolism: physiology and pathophysiology

Disturbances in mineral homeostasis are common in the neonatal period, especially in premature infants and infants who are hospitalised in an intensive care unit. In many cases these disturbances are thought to be exaggerated responses to the normal physiological transition from the intrauterine environment to neonatal independence. By contrast, some disturbances in calcium homeostasis are the result of genetic defects, which in many instances can now be identified at the molecular level. In other cases hypocalcaemia or hypercalcaemia may result from pathological intrauterine conditions, birth trauma or stress, or fetal immaturity. Diagnosis and management of hypocalcaemia and hypercalcaemia in the neonate and infant requires specific knowledge of perinatal mineral physiology and the unique clinical and biochemical features of newborn mineral metabolism. In this chapter we will provide a brief overview of calcium metabolism with an emphasis on the neonatal transition, followed by discussion of the common causes of hypercalcaemia and hypocalcaemia.

Kenny-Caffey syndrome: an Arab variant?

We describe 2 unrelated Bedouin girls who met the criteria for the diagnosis of Kenny-Caffey syndrome. The girls had some unusual features--microcephaly and psychomotor retardation--that distinguish the Kenny-Caffey syndrome profile in Arab children from the classical Kenny-Caffey syndrome phenotype characterized by macrocephaly and normal intelligence. The 2 girls did not harbor the 22q11 microdeletion (the hallmark of the DiGeorge cluster of diseases) that we previously reported in another Bedouin family with the Kenny-Caffey syndrome (Sabry et al. J Med Genet 1998: 35(1): 31-36). This indicates considerable genetic heterogeneity for this syndrome. We also review previously reported 44 Arab/Bedouin patients with the same profile of hypoparathyroidism, short stature, seizures, mental retardation and microcephaly. Our results suggest that these patients represent an Arab variant of Kenny-Caffey syndrome with characteristic microcephaly and psychomotor retardation. We suggest that all patients with Kenny-Caffey syndrome should be investigated for the 22q11 microdeletion. Other possible genetic causes for the Kenny-Caffey syndrome or its Arab variant include chromosome 10p abnormalities.

The autosomal recessive Kenny-Caffey syndrome locus maps to chromosome 1q42-q43

Kenny-Caffey syndrome (KCS) is an osteosclerotic bone dysplasia with associated hypocalcemia and ocular abnormalities. Both autosomal dominant (MIM127000) and autosomal recessive (MIM244460) inheritance patterns have been described. Using eight consanguineous Kuwaiti kindreds, a genome-wide search for linkage to the gene causing the autosomal recessive form of KCS was performed with polymorphic short tandem repeat markers. Significant linkage to a locus situated at chromosome 1q42 --> q43 with a maximal two-point lod score of 13.30 with marker D1S2649 was obtained. Haplotype analysis of flanking markers identified recombination events defining the KCS locus to a region between markers D1S2800 on the centromeric boundary and D1S2850 on the telomeric boundary, an approximately 4-cM interval. All affected individuals in these unrelated kindreds were homozygous for identical alleles at markers D1S2649 and D1S235, suggesting a single ancestral mutation underlying the disease in these families. Haploinsufficiency at 22q11, reported in another consanguineous KCS kindred, was not documented in these families.

Kenny-Caffey syndrome and microorchidism

We report on two adolescent boys with Kenny-Caffey syndrome and microorchidism. The first patient had elevated levels of serum follicle-stimulating hormone, but normal levels of luteinizing hormone and testosterone. There was no evidence of a microdeletion of the Y chromosome. The second patient had Leydig cell hyperplasia with normal seminiferous tubules and spermatogenesis, and normal pituitary histologic findings at autopsy. The presence of microorchidism in these patients confirms the previous observations and suggests subfertility, but does not fully clarify the pathogenesis.

Kenny-Caffey syndrome is part of the CATCH 22 haploinsufficiency cluster

We report four sibs with Kenny-Caffey syndrome in a consanguineous Bedouin family. The first two died in the neonatal period while the remaining affected brother and sister had all the characteristic clinical, biochemical, and radiological abnormalities of the syndrome. These included severe pre- and postnatal growth retardation, cortical thickening of the tubular bones with medullary stenosis, eye abnormalities, facial dysmorphism, hypocalcaemia, and low levels of parathyroid hormone. The children also showed intracranial calcification, impaired neutrophil phagocytosis, increased proportion of B lymphocytes, reduced CD4 and CD8 subpopulations of T lymphocytes, and inhibited transformation in response to Candida antigen. Fluorescence in situ hybridisation (FISH) was applied to blood lymphocyte metaphase spreads from these two Bedouin sibs and their parents using probe D22S75 (Oncor), specific for the DiGeorge critical region on chromosome 22q11.2. The presence of 22q11.2 haploinsufficiency was identified in the affected sibs, which was transmitted from the phenotypically normal mother. The present report widens the spectrum of CATCH 22 microdeletion to accommodate Kenny-Caffey syndrome.