Cystic fibrosis has been largely under-diagnosed and thus, limited data is available on the incidence of cystic fibrosis in Sri Lanka. Our aim is to describe the phenotypic and genotypic spectrum of children with cystic fibrosis in Sri Lanka. This report describes 10 unrelated cystic fibrosis cases with phenotypic features of cystic fibrosis and abnormal or intermediate sweat tests. The most common phenotypic features in this sample of symptomatic patients were persistent or recurrent lower respiratory tract infections, failure to thrive and Pseudo-Bartter syndrome. Altogether 7 cystic fibrosis causing mutations were identified in 10 patients. Except delta F508 which is the commonest mutation worldwide all the other mutations detected in Sri Lankan patients are rare mutations. 1161delC and V456A detected in our patients are South Asian mutations. The other mutations such as [C.1282C > G; C.2738A > G], C.53 + 1G > C, 2184insA and a deletion encompassing exons 4 to 11 have been reported previously from European patients with cystic fibrosis. These cases highlight the importance of considering the diagnosis of cystic fibrosis in children and young adults presenting with persistent respiratory tract infections associated with severe malnutrition and Pseudo-Bartter syndrome, especially in low income countries where newborn screening for cystic fibrosis is not available. The spectrum of CFTR mutations in Sri Lanka is heterogeneous and possibly linked to genetic flow from Indian subcontinent and Europe. The common mutations should be identified by sequencing the entire CFTR gene in adequate number of cystic fibrosis patients in order to design a mutation panel for common regional mutations.

Acute intermittent porphyria is a rare autosomal dominant disorder caused by a deficiency of the enzyme, hydroxymethylbilane synthase. Recognition of acute neurovisceral attacks can be difficult due to the nonspecific nature of symptoms. We report a case of 33-year-old male patient who presented with recurrent episodes of severe abdominal pain, nausea, vomiting, constipation and numbness of bilateral lower limb extremities. These nonspecific neurovisceral attacks were subject to medical and surgical misdiagnoses of acute appendicitis, sinus tachycardia, renal calculi, drug-induced acute interstitial nephritis and two episodes of partial intestinal obstruction. The sixth acute attack raised the suspicion of an acute porphyria. Watson and Schwartz test was positive for porphobilinogen in urine. Mutation analysis by DNA sequencing of the extracted DNA of the proband revealed a previously reported missense mutation, c.517C>T encoding p.R173W in the HMBS gene, confirming the diagnosis of Acute Intermittent Porphyria. Four out of five family members who underwent targeted mutation analyses were mutation-positive. The most common clinical presentation of Acute Intermittent Porphyria is abdominal pain with neurovisceral manifestations which are common to several medical, psychiatric and surgical pathologies. This leads to underdiagnosis and misdiagnosis of this disorder, incorrect management, and severe complications. Therefore, a high index of suspicion and awareness of front line laboratory investigations are important for diagnosis. Definitive diagnosis enables implementation of strategies to prevent acute attacks, and also triggers genetic testing and genetic counseling of at-risk family members.

Renal hypouricemia is a rare heterogeneous inherited disorder characterized by impaired tubular uric acid transport, reabsorption insufficiency and /or acceleration of secretion. The affected individuals are predisposed to nephrolithiasis and recurrent episodes of exercise-induced acute kidney injury. Type 1 is caused by dysfunctional variants in the SLC22A12 gene (URAT1), while type 2 is caused by defects in the SLC2A9 gene (GLUT9). To date, more than 150 patients with the loss-of-function mutations for the SLC22A12 gene have been found (compound heterozygotes and/or homozygotes), most of whom are Japanese and Koreans. Herein, we report a nine year old Sri Lankan boy with renal hypouricemia (serum uric acid 97 μmol/L, fractional excretion of uric acid 33%).The sequencing analysis of SLC22A12 revealed a potentially deleterious missense variant c.1400C > T (p.T467 M, rs200104135) in heterozygous state. This variant has been previously identified in homozygous and/or compound heterozygous state with other causative SLC22A12 variant c.1245_1253del (p.L415_G417del) in Roma population. This is the first identification of a family with mild renal hypouricemia1 associated to the p.T467 M variant. Detailed investigations of urate blood and urine concentrations in patients with unexplained hypouricemia are needed and renal hypouricemia should also be considered in patients other than those from Japan and/or Korea. Our finding confirms an uneven geographical and ethnic distribution of Romany prevalent SLC22A12 variant that need to be considered in Asian patients (population data Genome Aggregation Database: allele frequency in South Asia 0.007055, in East Asia 0.001330).

Uric acid is the metabolic end product of purine metabolism in humans. Altered serum and urine uric acid level (both above and below the reference ranges) is an indispensable marker in detecting rare inborn errors of metabolism. We describe different case scenarios of 4 Sri Lankan patients related to abnormal uric acid levels in blood and urine. A one-and-half-year-old boy was investigated for haematuria and a calculus in the bladder. Xanthine crystals were seen in microscopic examination of urine sediment. Low uric acid concentrations in serum and low urinary fractional excretion of uric acid associated with high urinary excretion of xanthine and hypoxanthine were compatible with xanthine oxidase deficiency. An 8-month-old boy presented with intractable seizures, feeding difficulties, screaming episodes, microcephaly, facial dysmorphism and severe neuro developmental delay. Low uric acid level in serum, low fractional excretion of uric acid and radiological findings were consistent with possible molybdenum cofactor deficiency. Diagnosis was confirmed by elevated levels of xanthine, hypoxanthine and sulfocysteine levels in urine. A 3-year-10-month-old boy presented with global developmental delay, failure to thrive, dystonia and self-destructive behaviour. High uric acid levels in serum, increased fractional excretion of uric acid and absent hypoxanthine–guanine phosphoribosyltransferase enzyme level confirmed the diagnosis of Lesch–Nyhan syndrome. A 9-year-old boy was investigated for lower abdominal pain, gross haematuria and right renal calculus. Low uric acid level in serum and increased fractional excretion of uric acid pointed towards hereditary renal hypouricaemia which was confirmed by genetic studies. Abnormal uric acid level in blood and urine is a valuable tool in screening for clinical conditions related to derangement of the nucleic acid metabolic pathway.

Tetrahydrobiopterin (BH4) deficiencies are disorders affecting phenylalanine homeostasis, and catecholamine and serotonin biosynthesis. GTP-Cyclohydrolase I deficiency (OMIM 600225) is an extremely rare variant of inborn error of BH4 synthesis which exists in recessive and dominant forms. The recessive form presents with complex neurological and autonomic dysfunction whilst the dominant form presents as Dopa-responsive dystonia. We describe a South Asian child who initially presented with neurological dysfunction and recurrent vomiting and later developed recurrent hyperthermia for several months. The child did not have screening for hyperphenylalaninemia at birth and was found to have marked hyperphenylalaninemia after clinical presentation at 5 months. Further evaluation revealed BH4 deficiency. GTP-Cyclohydrolase I deficiency (GTPCH) was identified based on normal dihydro pteridine reductase activity and markedly reduced neopterin in dried blood spot test. After institution of treatment and control of high phenylalanine levels, clinical deterioration decelerated yet with noticeable residual neurological dysfunction. To authors’ knowledge, this is first report of GTPCH deficiency in a South Asian child. The case highlights practical issues regarding diagnosis of GTPCH deficiency, especially in countries without broader universal newborn screening programs for early detection of inherited metabolic disorders. Testing for GTPCH deficiency should be considered for patients with unexplained neurological and autonomic symptoms following initial metabolic screen.

Background: Fabry disease is a rare inborn error of metabolism with profound clinical consequences if untreated. It is caused by the deficiency of α galactosidase A enzyme and is the only lysosomal storage disorder with an X linked inheritance. Confirmation requires genetic analysis of Galactosidase Alpha (GLA) Gene, which is often a challenge in resource-poor settings. Despite these technological limitations, specific clinical features in this condition can establish the diagnosis. Case presentation: We report on a 13-year old male who presented with an afebrile convulsion with a background history of chronic burning sensation of hands and feet and anhidrosis for 2 years duration with a similar history of episodic acroparesthesia in the other male sibling. The early clinical diagnosis was based on the history and detection of Cornea Verticillata on eye examination. Biochemical confirmation was established with detection of low α galactosidase A enzyme levels and a missense mutation of the Galactosidase Alpha (GLA) Gene (c.136C > T) established the genetic confirmation. Conclusion: This is the first case of Fabry disease reported in Sri Lanka. Awareness of specific clinical features aided clinical diagnosis long before access to genetic confirmation was available.