Multiplexed cell-based diagnostic devices for detection of renal biomarkers.

The number of synthetic biology-based solutions employed in the medical industry is growing every year. The whole cell biosensors being one of them, have been proven valuable tools for developing low-cost, portable, personalized medicine alternatives to conventional techniques. Based on this concept, we targeted one of the major health problems in the world, Chronic Kidney Disease (CKD). To do so, we developed two novel biosensors for the detection of two important renal biomarkers: urea and uric acid. Using advanced gene expression control strategies, we improved the operational range and the response profiles of each biosensor to meet clinical specifications. We further engineered these systems to enable multiplexed detection as well as an AND-logic gate operating system. Finally, we tested the applicability of these systems and optimized their working dynamics inside complex medium human blood serum. This study could help the efforts to transition from labor-intensive and expensive laboratory techniques to widely available, portable, low-cost diagnostic options.

A Delayed Presentation of Arginase Deficiency Presenting with Status Epilepticus.

Arginase 1(ARG1) deficiency is a rare disorder of the urea cycle. The presentation is usually late, leading to loss of intellectual milestones, spasticity and liver involvement. Hyperammonemic crises are rarely encountered. We herein present a case of a 16-year immigrant girl of Syrian origin who was evaluated for acute onset of fever, vomiting, and seizures. Laboratory analyses showed slightly elevated lactate, creatine kinase, and coagulation parameters. Ammonium levels were also moderately increased. On 5th day of admission, she went into an encephalopathic state. Blood amino acid analysis showed highly elevated arginine levels. An increased level of orotic acid was found in urine organic acid analysis. Molecular genetic analysis of ARG1 gene showed a novel homozygous mutation. Although the presentation of ARG1 deficiency is usually chronic in the majority of patients, an acute crisis of encephalopathy due to hyperammonemia may occur and delayed diagnosis may lead to irreversible neurological damage. Key Words: Urea cycle disorder, Hyperammonemia, Argininemia, Encephalopathy.

Decreased antioxidant capacity with serum native thiol and total thiol levels in children with hemophilia A: a prospective case-control study.

BACKGROUND: Experimental studies have addressed the role of oxidant stress in the pathogenesis of Hemophilia A. This study aimed to determine whether dynamic thiol-disulfide exchange, a recently recognized cellular defense system against oxidative stress, is disturbed in children with hemophilia A. METHODS: This prospective case control study included male children with hemophilia A (n=62) and randomly selected healthy age and sex-matched controls (n=62). Serum native thiol, total thiol and disulfide levels were analyzed with a novel spectrophotometric method. Ratios of disulfide/total thiol, disulfide/native thiol, and native/total thiol were calculated. Statistical comparisons were made using the independent samples t-test or the Mann-Whitney U test, according to whether the data were normally distributed or not. RESULTS: Serum native thiol (385.0 ± 35.9 versus 418.0 ± 44.3, respectively; p < 0.001) and total thiol (424.2 ± 38.7 versus 458.0 ± 46.3, respectively; p > 0.001) levels were significantly lower in children with Hemophilia A compared to controls. Children with hemophilia A had significantly lower serum native thiol to total thiol ratio than controls (p=0.024). Serum disulfide levels of children with hemophilia A were close to controls (19.2 [17.6- 22.1] versus 19.8 [17.8- 21.2]), respectively; p=0.879) whereas disulfide to native thiol ratio (p=0.024) and disulfide to total thiol ratio (p=0.024) were significantly higher. CONCLUSIONS: Decreased antioxidant capacity with levels of serum native thiol and total thiol in children with hemophilia A might be regarded as evidence for the disturbance of thiol/disulfide balance. Antioxidant treatment can be a future target of therapy in children with hemophilia A.

Congenital Rare Diseases Causing Persistent Diarrhea in the Newborn: A Single Center Experience.

Congenital diarrheal disorders (CDDs) are a heterogeneous group of inherited diseases that typically occur in the first weeks of life or can present later in life after the introduction of different nutrients; they can cause life-threatening severe dehydration and electrolyte disturbances. This study was conducted to characterize the causes of monogenic CDDs, and their clinical consequences. Clinical characteristics of 31 patients with CDDs that occurred in the first month of life and lasted more than 2 weeks were analyzed retrospectively. The patients were divided into groups according to the current CDD classification. The rate of consanguinity among parents was 77.4%. Of the patients, 16 (51.6%) were female and 15 (48.4%) were male. The underlying genetic defect was determined in 26 (83.9%) patients. The most common etiologic factors were digestive disorders of food and absorption and transport of electrolytes (58.1%, 18/31) (most of them being carbohydrate malabsorption disorders, 12/18) and intestinal immune system disorders (9.6%, 3/31). Total parenteral nutrition (TPN) was given to 45.2% (14/31) of the patients. Mortality rate was 28.5% (8/28). In conclusion, early diagnosis and treatment of CDDs with high morbidity and mortality is extremely important in terms of prognosis. Clinical and laboratory findings, stool characteristics, histopathological findings and the effects of dietary therapy are the primary and most important steps that lead to accurate diagnosis. In addition, advanced diagnostic possibilities, including genetic analyses, are essential for diagnosing underlying diseases.

SRD5A3-CDG: A Patient with a Novel Variant and Brain Neoplasm.

Congenital disorders of glycosylation (CDGs) are a large group of genetic diseases with impaired glycosylation of glycoproteins and glycolipids, and glycosylphosphatidylinositol anchor synthesis. Steroid 5α-reductase 3 (SRD5A3)-CDG is a CDG type I with a clinical spectrum of neurological, ophthalmological, dermatological and hepatic symptoms. Although CDGs are not directly related to malignancies, it is well known that some genes that are involved in glycosylation pathways are involved in various cancers. Aberrant glycosylation has been closely linked to the development and progression of brain cancer. We report a patient with SRD5A3-CDG carrying a novel homozygous splice variant and brain neoplasm. Also, a review of the literature is made regarding the multisystem effects of the disease. Key Words: SRD5A3-CDG, Glioma, Glycosylation, Transferrin isoelectric focusing, Congenital disorders of glycosylation.

MAN1B1-CDG: novel patients and novel variant.

OBJECTIVES: Congenital disorders of glycosylation (CDGs) are a group of genetic disorders due to hypoglycosylation of proteins and lipids. A type I pattern is associated with defects in glycan assembly and transfer (CDG-I; cytosol; and endoplasmic reticulum defects), a type II pattern is seen in processing defects of the Golgi apparatus. MAN1B1-CDG is an autosomal recessive CDG-II due to mutations in the α 1,2-mannosidase gene (MAN1B1), mainly characterized by psychomotor disability, facial dysmorphism, truncal obesity, and hypotonia. CASE PRESENTATION: Three patients (two males and one female), with MAN1B1-CDG who had elevated transaminase levels are presented. All patients had presented due to dysmorphic and neurological findings and hypertransaminasemia was remarkable. A type 2 pattern was found on serum transferrin isoelectrofocusing analysis of the presented cases. MAN1B1-CDG was confirmed by genetic analysis. CONCLUSIONS: Although the cause of the increased serum transaminase levels in the present patients is not clear, no evidence for an infection or underlying liver pathology could be identified. In order to know if this is a consistent feature, we suggest measuring serum transaminase levels regularly in MAN1B1-CDG patients.

Retrospective evaluation of patients with X-linked adrenoleukodystrophy with a wide range of clinical presentations: a single center experience.

OBJECTIVES: X-linked adrenoleukodystrophy (X-ALD), is a peroxisomal inborn error of metabolism caused due to the loss of function variants of ABCD1 gene that leads to accumulation of very long chain fatty acids (VLCFAs) in several tissues including the neurological system. Childhood cerebral X-ALD (CCALD) is the most common and severe form of X-ALD, if left untreated. Allogenic hematopoietic stem cell transplantation (HSCT) is the only available therapy that halts neurological deterioration in CCALD. We present 12 patients with several subtypes of X-ALD that were followed-up in a single center. METHODS: Data of 12 patients diagnosed with X-ALD were documented retrospectively. Demographics, age of onset, initial symptoms, endocrine and neurological findings, VLCFA levels, neuroimaging data, molecular genetic analysis of ABCD1 gene, and disease progress were documented. RESULTS: Mean age of initiation of symptoms was 7.9 years and mean age of diagnosis was 10.45 years. Eight patients had the CCALD subtype, while two had the cerebral form of AMN, one had the adult form of cerebral ALD, and one patient had the Addison only phenotype. The most common initial symptoms involved the neurological system. Loes scores varied between 0 and 12. Seven patients with CCALD underwent HSCT, among them three patients died. The overall mortality rate was 25%. CONCLUSIONS: Patients with X-ALD should be carefully followed up for cerebral findings and progression, since there is no genotype-phenotype correlation, and the clinical course cannot be predicted by family history. HSCT is the only available treatment option for patients with neurological deterioration.

Oxidative Stress in Intoxication Type Inborn Errors of Metabolism using Thiol-Disulfide Ratio.

OBJECTIVE: To determine the relationship of oxidative stress status with follow-up parameters, metabolic control status, and treatment compliance evaluation in patients diagnosed within toxication type inherited metabolic disease (IMDs). STUDY DESIGN: Descriptive, analytical study. PLACE AND DURATION OF STUDY: Dr. Sami Ulus, Maternity and Child Health, Training and Research Hospital, Ankara, Turkey, between September 2019 and March 2020. METHODOLOGY: Sixty-seven patients, who were followed up with a diagnosis of IMDs in the pediatric metabolism outpatient clinic, and 41 healthy volunteers who applied to the social pediatrics outpatient clinic, were evaluated. ​Disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol ratios of the patient and control group were calculated. P <0.05 (*) value was considered significant in statistical analysis. RESULTS: The mean native thiol / total thiol ratio of the patient group was significantly lower when compared to the control group (92.0±3.3 vs 94.1±2.7, p=0.001). The median disulfide level [19.8 (11.6-25) vs 14(10.1-18.8), p=0.004], the mean disulfide / native thiol (4.5±2.0 vs 3.2±1.6, p<0.001) and the mean disulfide / total thiol ratios (4.0±1.7 vs 2.9±1.4, p=0.001) were higher in the patient group compared to the control group.The findings showed that oxidative stress status was increased during metabolic attacks. Poor metabolic control and non-compliance to treatment was found to be associated with increased oxidative stress. Oxidative stress parameters were found to be correlated with metabolic chemicals such as ammonia, leucine, and citrulline. There was no correlation between phenylalanine and lactate levels and oxidative stress parameters. CONCLUSION:  Metabolic control status and compliance with treatment are related to oxidative stress level, showing thiol/disulfide balance in urea cycle defects, phenylketonuria, and galactosemia patients. Key Words: Thiol / disulfide, Metabolic diseases, MSUD, Galactosemia, Hyperammonemia.

Genotypic and phenotypic features in Turkish patients with classic nonketotic hyperglycinemia.

Nonketotic hyperglycinemia is an autosomal recessive inborn error of glycine metabolism, characterized by deficient activity of the glycine cleavage enzyme system. Classic nonketotic hyperglycinemia is caused by mutations or genomic changes in genes that encode the protein components of the glycine cleavage enzyme system. We aimed to investigate clinical, biochemical, radiological findings and molecular genetic data in ten Turkish patients with classic nonketotic hyperglycinemia. Ten Turkish patients who were diagnosed with classic nonketotic hyperglycinemia in a single center from 2013 to 2019 were included in this study. Their clinical, radiological, electrophysiological and laboratory data were collected retrospectively. Sixty percent of the patients were in neonatal group, while 40 % of the patients were infantile. There were no late-onset patients. 90 % of the patients had the severe form. All patients had developmental delay and seizures. Mortality ratio was 30 % in all groups and 50 % in the neonatal group, while no mortality was seen in infantile group. Median (range) values of cerebrospinal fluid (CSF) glycine levels, plasma glycine levels and CSF/plasma glycine ratios were 148 (15-320) µmol/L, 896 (87-1910) µmol/L, 0.17 (0.09-0.21) respectively. Diffuse hypomyelination and corpus callosum anomaly were the most common cranial MRI findings and multifocal epileptic activity and burst supression pattern were the most common electroencephalographic findings. Six patients had variants in GLDC gene and four in AMT gene; five novel variants including AMT gene deletion were detected. Prognosis was poor and treatment was not effective, especially in the severe form. Classic nonketotic hyperglycinemia causes high morbidity and mortality. Neonatal-onset disease was more common and severe than infantile-onset disease. The ratio of AMT gene variants might be higher in Turkey than other countries. AMT gene deletion also plays a role in the etiology of classic nonketotic hyperglycinemia.

Un trastorno poco frecuente del ciclo de la urea en un recién nacido: deficiencia de N-acetilglutamato sintasa / A rare urea cycle disorder in a neonate: N-acetylglutamate synthetase deficiency

Los trastornos del ciclo de la urea (TCU) son enfermedades hereditarias con un posible desenlace desfavorable por hiperamoniemia grave. Se informa de una bebé con deficiencia de N-acetilglutamato sintasa (NAGS), quien tenía succión débil e hipotonicidad. Al examinarla, se observó hepatomegalia. El hemograma, los análisis y la gasometría eran normales, y las proteínas de la fase aguda, negativas. En los análisis, no se observaron cetonas en sangre, pero sí concentraciones elevadas de amoníaco. Las pruebas metabólicas no fueron concluyentes. Se inició el tratamiento de emergencia inmediatamente y recibió el alta el día 15 después del ingreso. Se confirmó deficiencia de NAGS mediante análisis de ADN. La paciente no tiene restricciones alimentarias ni toma medicamentos, excepto N-carbamil glutamato (NCG). La deficiencia de NAGS es el único TCU que puede tratarse específica y eficazmente con NCG. La detección temprana permite iniciar un tratamiento temprano y evitar los efectos devastadores de la hiperamoniemia

Urea cycle disorders (UCD), are genetically inherited diseases that may have a poor outcome due to to profound hyperammonemia. We report the case of a baby girl diagnosed as N-acetylglutamate synthase (NAGS) deficiency.The patient was evaluated due to diminished sucking and hypotonicity. Physical examination showed hepatomegaly. Complete blood count, biochemical values and blood gas analyses were normal, acute phase reactants were negative. Further laboratory analyses showed no ketones in blood and highly elevated ammonia. Metabolic tests were inconclusive. Emergency treatment was initiated immediately and she was discharged on the 15th day of admission. NAGS deficiency was confirmed by DNA-analysis. She is now without any dietary restriction or other medication, except N-carbamylglutamate (NCG).NAGS deficiency is the only UCD which can be specifically and effectively treated by NCG. Early recognition of disease will lead to early treatment that may prohibit devastating effects of hyperammonemia

A rare urea cycle disorder in a neonate: N-acetylglutamate synthetase deficiency. / Un trastorno poco frecuente del ciclo de la urea en un recién nacido: deficiencia de N-acetilglutamato sintasa.

Urea cycle disorders (UCD), are genetically inherited diseases that may have a poor outcome due to to profound hyperammonemia. We report the case of a baby girl diagnosed as N-acetylglutamate synthase (NAGS) deficiency. The patient was evaluated due to diminished sucking and hypotonicity. Physical examination showed hepatomegaly. Complete blood count, biochemical values and blood gas analyses were normal, acute phase reactants were negative. Further laboratory analyses showed no ketones in blood and highly elevated ammonia. Metabolic tests were inconclusive. Emergency treatment was initiated immediately and she was discharged on the 15th day of admission. NAGS deficiency was confirmed by DNA-analysis. She is now without any dietary restriction or other medication, except N-carbamylglutamate (NCG). NAGS deficiency is the only UCD which can be specifically and effectively treated by NCG. Early recognition of disease will lead to early treatment that may prohibit devastating effects of hyperammonemia.

Los trastornos del ciclo de la urea (TCU) son enfermedades hereditarias con un posible desenlace desfavorable por hiperamoniemia grave. Se informa de una bebé con deficiencia de N-acetilglutamato sintasa (NAGS), quien tenía succión débil e hipotonicidad. Al examinarla, se observó hepatomegalia. El hemograma, los análisis y la gasometría eran normales, y las proteínas de la fase aguda, negativas. En los análisis, no se observaron cetonas en sangre, pero sí concentraciones elevadas de amoníaco. Las pruebas metabólicas no fueron concluyentes. Se inició el tratamiento de emergencia inmediatamente y recibió el alta el día 15 después del ingreso. Se confirmó deficiencia de NAGS mediante análisis de ADN. La paciente no tiene restricciones alimentarias ni toma medicamentos, excepto N-carbamil glutamato (NCG). La deficiencia de NAGS es el único TCU que puede tratarse específica y eficazmente con NCG. La detección temprana permite iniciar un tratamiento temprano y evitar los efectos devastadores de la hiperamoniemia.

Carbonic anhydrase VA deficiency: a very rare case of hyperammonemic encephalopathy.

Objectives Carbonic anhydrase VA (CAVA) deficiency is a rare autosomal recessive inborn error of metabolism that leads to acute metabolic crises, especially in the neonatal or infantile period. It is caused by a deficiency of the enzyme CAVA, which is encoded by the CA5A gene. Case presentation Fifteen patients with homozygous pathogenic CA5A mutations involving 10 different lesions have been reported in the literature up to date. Main clinical and biochemical features of CAVA deficiency include lethargy, hyperammonemic encephalopathy, metabolic acidosis, elevated lactate and hypoglycemia. In most patients reported so far, a single metabolic decompensation attack has been reported, and they have remained stable thereafter with no further crisis. Conclusions We report the 16th case of CAVA deficiency, who was diagnosed by whole-exome sequencing and showed a typical course of the disease with normal development at 18 months.

Beneficial Effects of Modified Atkins Diet in Glycogen Storage Disease Type IIIa.

INTRODUCTION: Glycogen storage disease Type III (GSD III) is an autosomal recessive disease caused by the deficiency of glycogen debranching enzyme, encoded by the AGL gene. Two clinical types of the disease are most prevalent: GSD IIIa involves the liver and muscle, whereas IIIb affects only the liver. The classical dietetic management of GSD IIIa involves prevention of fasting, frequent feeds with high complex carbohydrates in small children, and a low-carb-high-protein diet in older children and adults. Recently, diets containing high amount of fat, including ketogenic and modified Atkins diet (MAD), have been suggested to have favorable outcome in GSD IIIa. METHODS: Six patients, aged 3-31 years, with GSD IIIa received MAD for a duration of 3-7 months. Serum glucose, transaminases, creatine kinase (CK) levels, capillary ketone levels, and cardiac parameters were followed-up. RESULTS: In all patients, transaminase levels dropped in response to MAD. Decrease in CK levels were detected in 5 out of 6 patients. Hypoglycemia was evident in 2 patients but was resolved by adding uncooked cornstarch to diet. CONCLUSION: Our study demonstrates that GSD IIIa may benefit from MAD both clinically and biochemically.

A rare case of primary coenzyme Q10 deficiency due to COQ9 mutation.

Background Coenzyme Q10 (CoQ10) serves as a shuttle for electrons from complexes I and II to complex III in the respiratory chain, and has important functions within the mitochondria. Primary CoQ10 deficiency is a mitochondrial disorder which has devastating effects, and which may be partially treated with exogenous CoQ10 supplementation. Case presentation A 9-month-old girl patient was referred to our clinic due to growth retardation, microcephaly and seizures. She was the third child of consanguineous parents (first-degree cousins) of Pakistani origin, born at 38 weeks gestation, weighing 2000 g after an uncomplicated pregnancy, and was hospitalized for 3 days due to respiratory distress. She had sustained clonic seizures when she was 4 months old. Physical examination showed microcephaly, truncal hypotonia and dysmorphic features. Metabolic tests were inconclusive. Abdominal ultrasonography revealed cystic appearance of the kidneys. Non-compaction of the left ventricle was detected in echocardiography. Cranial magnetic resonance imaging (MRI) showed hypoplasia of the cerebellar vermis and brain stem, corpus callosum agenesis, and cortical atrophy. A panel testing of 450 genes involved in inborn errors of metabolism (IEM) was performed that showed a novel frameshift c.384delG (Gly129Valfs*17) homozygous mutation in COQ9. A treatment of 5 mg/kg/day exogenous CoQ10 was started when she was 10 months old, and the dosage was increased to 50 mg/kg/day after the exact diagnosis. No objective neurological improvement could be observed after the adjustment of the drug dosage. Conclusions We report a case of CoQ10 deficiency due to a novel COQ9 gene mutation that adds clinical data from a newly diagnosed patient. Our case also outlines the importance of genetic panels used for specific diseases including IEM.

Vitamin D Levels and Bone Mineral Density in Inborn Errors of Metabolism Requiring Specialised Diets.

OBJECTIVE: To evaluate vitamin D levels and bone mineral density in patients with dietary limitations due to inborn errors of metabolism (IEM) and its correlation with diets. STUDY DESIGN: Retrospective study. PLACE AND DURATION OF STUDY: Department of Pediatrics, Division of Pediatric Metabolism and Nutrition, Gazi University Hospital, Turkey, from March to Semtember 2016. METHODOLOGY: The study is a retrospective review of 115 patients. Information about vitamin D status, bone mineral density (BMD) measurement and anthropometric parametres were collected. Patients were divided into two major groups, receiving protein-restricted diets (n=83) and lactose-restricted diets (n=32). Data of 110 healthy children were used as the control group. RESULTS: Mean vitamin D level of patients with special diets 28.1 ±14.9 ng/ml while mean level of healthy controls was 26.6 ±12.27 ng/ml. Levels of 26.8% (n=26/97) patients were found to be deficient and 34% (n=33/97) were found to be insufficient. No statistically significant differences were found between vitamin D levels and BMD of patients and healthy controls. BMD was not influenced by vitamin D levels. CONCLUSION: Low BMD may be encountered in IEM, independent of vitamin D levels and revision of diet for adequacy of essential nutrients; and follow-up for dietary compliance is inevitable.

An infant with an extremely rare cobalamin disorder: Methionine synthase deficiency and importance of early diagnosis and treatment.

Kasapkara ÇS, Yilmaz-Keskin E, Özbay-Hosnut F, Akçaboy M, Polat E, Olgaç A, Zorlu P. An infant with an extremely rare cobalamin disorder: Methionine synthase deficiency and importance of early diagnosis and treatment. Turk J Pediatr 2019; 61: 282-285. Functional methionine synthase deficiency can be separated into two classes, cobalamin (Cbl) deficiency type E (CblE) and type G (CblG), which are the result of mutations that affect methionine synthase reductase or methionine synthase, respectively. Deficiency of methionine synthase activity may result in megaloblastic anemia without methylmalonic aciduria and neuromuscular abnormality of varying severity. Delayed milestones, ataxia, cerebral atrophy, muscular hypotonia, neonatal seizures, and blindness have been reported as the associated clinical findings. Early diagnosis and treatment are crucial for a more favorable diagnosis of the affected cases. Herein we report a three-month-old boy with CblG disease who presented with failure to thrive, chronic diarrhea, feeding intolerance, oral ulcers, microcephaly and hypotonia, and showed a dramatic response to treatment. In the first few months of life, megaloblastic anemia accompanied by apparent neurological involvement should direct physicians to order examinations like measurement of total homocysteine and methylmalonic acid levels to detect possible forms of inherited Cbl intracellular metabolism disorders.

Patient With Niemann-Pick Type C Presenting With a Jaw Mass Characterized With Lymph Node Involvement by Niemann-Pick Cells.

Niemann-Pick type C disease (NPC) is an autosomal recessive disorder resulting in accumulation of unesterified lysosomal cholesterol. An 8-year-old girl with NPC disease had a painless, rigid, and fixed mass measuring 3 cm in diameter located on the left angular region of mandibula. The mass biopsy showed lipid-laden phagocytic cells infiltrating the lymph node consistent with Niemann-Pick cells. In NPC, accumulation of cholesterol in tissues could be seen not only in reticuloendothelial and nervous systems, but also in all systems. Our case is important for it being the first case of NPC with submandibular lymphadenopathy characterized with NPC cell infiltration.

A Newborn with an Alternative Porto-Caval Shunt.

BACKGROUND: Absent ductus venosus (ADV) is a rare condition, but it should be known that this embryonic anomaly may be detected by fetal echocardiographic or newborn ultrasound examinations. CASE REPORT: We present a baby with an ADV and an accompanying alternative porto-caval shunt between the right portal vein and inferior vena cava detected on postnatal ultrasound examination. CONCLUSIONS: Variations in the fetal umbilical or porto-systemic circulations should be detected by fetal or newborn ultrasound examinations and kept in mind before common interventions such as UV catheterizations.

Diagnostic dilemma: osteopetrosis with superimposed rickets causing neonatal hypocalcemia.

Osteopetrosis is a rare genetic condition of reduced osteoclastic bone resorption which causes defective bone remodeling and skeletal sclerosis during growth, having effects on many organs and tissues. Mutation of T-cell immune regulator 1 (TCRG1) gene is the most common genetic defect leading to osteopetrosis, with poor prognosis. The autosomal recessive form presents in the infantile period (also known as malignant infantile osteopetrosis--MIOP), and is characterized by fractures, short stature, hepatosplenomegaly, compressive neuropathies, hypocalcemia and pancytopenia. Being a rare disease with non-specific clinical manifestations, the diagnosis is difficult and usually delayed. Rickets is a characteristic feature of MIOP which results from the defect in osteoclasts to provide a normal Ca/P balance resulting in the poor mineralization of the osteoid. Various treatment options have been suggested for osteopetrosis, but hematopoietic stem cell transplantation still remains the only curative treatment option presently. The authors report the case of a 46-day-old girl with late-onset neonatal hypocalcemia and rickets that was later diagnosed as osteopetrosis. This case report emphasizes that infantile osteopetrosis is an important cause of neonatal hypocalcemia. As irreversible complications develop within the first months of life, immediate diagnosis and early intervention are crucial and may be life-saving.