Adenosine deaminase 2 (ADA2) deficiency is a cause of vasculopathy that is coded by the CECR1 (Cat Eye Syndrome Chromosome Region 1) gene and that causes overlapping with polyarteritis nodosa (PAN) as a result of recessive mutations. ADA2 is both a major extracellular adenosine deaminase and an adenosine deaminase-related growth factor. In humans, the irreversible degradation of adenosine to inosine and deoxyadenosine to deoxyinosine is catalyzed by intracellular ADA1 and extracellular ADA2. 1 Recessive ADA1 mutations are a well-known cause of severe combined immune deficiency. However, ADA2 deficiency manifests as increased vascular inflammation without clinically apparent immune deficiency. This vasculopathy is characterized by highly varied age at onset, severity, and organ involvement, even within families and among patients with the same mutations. Manifestations range from severe or fatal systemic vasculitis or multiple strokes to limited cutaneous manifestations in children. 2 This disease encloses a wide spectrum of vascular and inflammatory manifestations, including earlyonset strokes, recurrent fevers, and systemic vasculopathy, which is often consistent with PAN. 3

In conclusion, eculizumab may be a treatment of choice to prevent further systemic damage in recurrent HUS episodes of patients with borderline changes in the bone marrow until ALL is constantly diagnosed.

Alparslan C, Öncel EP, Akbay S, Alaygut D, Mutlubaş F, Tatlı M, Konrad M, Yavaşcan Ö, Kasap-Demir B. A novel homozygous W99G mutation in CLDN-16 gene causing familial hypomagnesemic hypercalciuric nephrocalcinosis in Turkish siblings. Turk J Pediatr 2018; 60: 76-80. Familial hypomagnesemic hypercalciuric nephrocalcinosis (FHHNC) (OMIM: 248250) is characterized by hypomagnesemia, hypercalciuria and nephrocalcinosis. FHHNC inevitably progresses to end-stage renal disease in decades. Mutations in CLDN-16 and CLDN-19 genes are associated with disrupted magnesium handling in the thick ascending limp of Henle`s loop. Patients with mutations in these genes share similar clinical features, and those with CLDN-19 gene mutations have ocular findings in addition. A 2-month-old boy, was admitted to our clinic with the complaints of upper respiratory tract infection. He was the first-born child of consanguineous parents. Laboratory findings revealed hypocalcemia and hypomagnesemia. Bilateral medullary nephrocalcinosis was detected on abdominal ultrasound. His ophthalmologic examination was unremarkable. With hypomagnesemia, hypercalciuria and nephrocalcinosis, the patient was considered to have FHHNC. Oral magnessium supplementation was initiated. Four years of follow-up has been completed uneventfully. When 6-days-old the brother of the case above was admitted with seizure. The patient was resistant to calcium and anticonvulsant drugs and the seizure activity could only be controlled after magnesium infusion. Biochemistry profile revealed hypocalcemia and hypomagnesemia. Urinary calcium extraction was 11 mg/kg/day. Medullary nephrocalcinosis was reported on renal ultrasound. His eye examination, echocardiography, transfontanel ultrasound and electroencephalography were normal. Due to the triad of hypomagnesemia, hypercalciuria and nephrocalcinosis, and the medical history of his elder brother, he was diagnosed with FHHNC. After correction of the electrolyte abnormalities, he was discharged from hospital and is currently being followed-up without any problem. In this manuscript, we shared our experience about a novel homozygous mutation (W99C) in CLDN-16 gene causing FHHNC in a couple of Turkish siblings.

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Background. Isolated sulfite oxidase deficiency (ISOD), caused by mutations in SUOX gene, is an autosomal recessive disease manifesting with early onset seizures, developmental delay, microcephaly, and spasticity. It mimics hypoxic-ischemic encephalopathy (HIE) in the neonatal period and is characterized by progressive severe neurological impairment due to accumulation of toxic metabolites.Case. This report presents a late diagnosed male patient with ISOD manifesting with neonatal-onset seizures, developmental delay, microcephaly, and spastic quadriplegia. Brain magnetic resonance imaging of the patient showed bilateral subcortical multi-cystic encephalomalacia involving bilateral parieto-occipital regions. A novel homozygous c.590_595delAGCCTC in-frame deletion in SUOX gene was identified in the patient, while both parents were heterozygous for that mutation. Conclusion.The mutation identified in our patient causes severe ISOD. Early diagnosis of ISOD is essential for accurate genetic counseling and achieving prenatal diagnosis. Screening for urinary sulfite in patients with neonatal or early infantile onset seizures, developmental delay, microcephaly and cystic encephalomalacia in neuroimaging mimicking HIE helps in early diagnosis.