Diagnostic Delay of Celiac Disease in Childhood

Importance

The extent and factors associated with risk of diagnostic delay in pediatric celiac disease (CD) are poorly understood.

Objectives

To investigate the diagnostic delay of CD in childhood, and to assess factors associated with this delay.

Design, Setting, and Participants

Multicenter, retrospective, cross-sectional study (2010-2019) of pediatric (aged 0-18 years) patients with CD from 13 pediatric tertiary referral centers in Italy. Data were analyzed from January to June 2023.

Main Outcomes and Measures

The overall diagnostic delay (ie, the time lapse occurring from the first symptoms or clinical data indicative of CD and the definitive diagnosis), further split into preconsultation and postconsultation diagnostic delay, were described. Univariable and multivariable linear regression models for factors associated with diagnostic delay were fitted. Factors associated with extreme diagnostic delay (ie, 1.5 × 75th percentile) and misdiagnosis were assessed.

Results

A total of 3171 patients with CD were included. The mean (SD) age was 6.2 (3.9) years; 2010 patients (63.4%) were female; and 10 patients (0.3%) were Asian, 41 (1.3%) were Northern African, and 3115 (98.3%) were White. The median (IQR) overall diagnostic delay was 5 (2-11) months, and preconsultation and postconsultation diagnostic delay were 2 (0-6) months and 1 (0-3) month, respectively. The median (IQR) extreme overall diagnostic delay (586 cases [18.5%]) was 11 (5-131) months, and the preconsultation and postconsultation delays were 6 (2-120) and 3 (1-131) months, respectively. Patients who had a first diagnosis when aged less than 3 years (650 patients [20.5%]) showed a shorter diagnostic delay, both overall (median [IQR], 4 [1-7] months for patients aged less than 3 years vs 5 [2-12] months for others) and postconsultation (median [IQR], 1 [0-2] month for patients aged less than 3 years vs 2 [0-4] months for others). A shorter delay was registered in male patients, both overall (median [IQR], 4 [1-10] months for male patients vs 5 [2-12] months for female patients) and preconsultation (median [IQR], 1 [0-6] month for male patients vs 2 [0-6] months for female patients). Family history of CD was associated with lower preconsultation delay (odds ratio [OR], 0.59; 95% CI, 0.47-0.74) and lower overall extreme diagnostic delay (OR, 0.75; 95% CI, 0.56-0.99). Neurological symptoms (78 patients [21.5%]; OR, 1.35; 95% CI, 1.03-1.78), gastroesophageal reflux (9 patients [28.1%]; OR, 1.87; 95% CI, 1.02-3.42), and failure to thrive (215 patients [22.6%]; OR, 1.62; 95% CI, 1.31-2.00) showed a more frequent extreme diagnostic delay. A previous misdiagnosis (124 patients [4.0%]) was more frequently associated with gastroesophageal reflux disease, diarrhea, bloating, abdominal pain, constipation, fatigue, osteopenia, and villous atrophy (Marsh 3 classification).

Conclusions and Relevance

In this cross-sectional study of pediatric CD, the diagnostic delay was rather short. Some factors associated with risk for longer diagnostic delay and misdiagnosis emerged, and these should be addressed in future studies.

Efficacy and Tolerance of Thalidomide in Patients With Very Early Onset Inflammatory Bowel Disease

BACKGROUND

Few drugs have been studied for patients with very early onset inflammatory bowel disease (VEOIBD). This study aimed to evaluate the efficacy and tolerance of thalidomide in children with VEOIBD compared with children with pediatric-onset IBD (pIBD).

METHODS

A retrospective cohort study with a control group was conducted. Propensity score 1:1 matching was used to identify control subjects. The treatment persistence; the causes of drug withdrawal; the rate of clinical remission and mucosal healing at 1, 2, and 3 years; and adverse events (AEs) were evaluated in children with VEOIBD treated with thalidomide and compared with children with pIBD.

RESULTS

Thirty-nine courses of treatment with thalidomide in VEOIBD and pIBD patients were compared. The treatment persistence at 1, 2, and 3 years was 68.2% (95% confidence interval [CI], 50.8%-80.6%), 57.0% (95% CI, 39.6%-71.1%), and 50.9% (95% CI, 33.7%-65.8%) for VEOIBD patients and 81.7% (95% CI, 65.3%-90.9%), 60.0% (95% CI, 41.7%-74.3%) and 33.0% (95% CI, 17.4%-49.5%) for pIBD patients, respectively (P = .12). A significantly higher proportion of VEOIBD patients discontinued therapy due to lack of efficacy (48.2% vs 17.2%; P = .03), while AEs were the main reason for discontinuation in pIBD patients. Clinical remission and mucosal healing rates did not significantly differ between VEOIBD and pIBD patients. A significatively lower number of VEOIBD patients experienced AEs compared with pIBD patients (14 [35.9%] vs 30 [76.9%]; P = .0005).

CONCLUSIONS

Thalidomide is an effective and tolerated treatment in children with VEOIBD. Discontinuation due to lack of efficacy is more frequent, but AEs are less common than in children with pIBD.

Paediatric porto-sinusoidal vascular disease: Two different clinical phenotypes with subtle histological differences

BACKGROUND AND AIMS

In paediatrics, porto-sinusoidal vascular disease (PSVD) is relatively unknown and probably underdiagnosed. We aimed to describe clinical phenotypes, histology and outcome of children diagnosed with PSVD.

METHODS

Retrospective multicentre study of children diagnosed with PSVD. Diagnosis of PSVD was based on histopathology reports; liver specimens were re-evaluated by two expert liver pathologists.

RESULTS

Sixty two children diagnosed with PSVD (M/F = 36/26, median age 6.6 years, range 3.3-10.6), from 7 centres, were included. Thirty-six presented with non-cirrhotic portal hypertension, PH, (PH-PSVD Group = 58%) while 26 had a liver biopsy because of chronic elevation of transaminases without PH (noPH-PSVD Group = 42%). On histology review, the two groups differed for the prevalence of obliterative portal venopathy (more prevalent in PH-PSVD, p = 0.005), and hypervascularised portal tracts (more common in noPH-PSVD, p = 0.039), the other histological changes were equally distributed. At multivariate analysis, platelet count ≤185 000/mm³ was the only independent determinant of PH (p < 0.001). After a median follow-up of 7 years (range 3.0-11.2), in PH-PSVD group 3/36 (8%) required TIPS placement, 5/36 (14%) developed pulmonary vascular complications of PH, and 7/36 (19%) required liver transplantation. In noPH-PSVD none progressed to PH nor had complications.

CONCLUSIONS

Paediatric patients with PSVD present with two different clinical phenotypes, one characterised by PH and one by chronic elevation of transaminases without PH. PSVD should be included among the conditions causing isolated hypertransaminasaemia. On histology, the differences between the two groups are subtle. Medium-term outcome is favourable in patients without PH; progression of the disease is observed in those with PH.

Gastrointestinal Disorders and Food Selectivity: Relationship with Sleep and Challenging Behavior in Children with Autism Spectrum Disorder

The aim of this study was to evaluate the interaction between gastrointestinal (GI) disorders, sleep problems, and challenging behaviors in children with a diagnosis of Autism Spectrum Disorder (ASD) and their effect on parental stress. The secondary objective was to assess the frequency and type of GI and feeding disorders in a sample of children with ASD through a multidisciplinary assessment and, finally, to investigate families' perceptions and satisfaction with the proposed multidisciplinary approach. All children underwent a comprehensive gastroenterological and neuropsychiatric evaluation supported by standardized questionnaires. Pediatric gastroenterologists, specifically trained in Applied Behavior Analysis (ABA), provided advice for parent-delivered behavioral intervention for food selectivity. Thirty-six children with an autism diagnosis (29 males, age 4.5 +/-2.2 years, mean +/- SD) were enrolled. A positive correlation between sleep problems and aggressive behavior was found, and this association was stronger in children experiencing more problematic mealtime behaviors (b = 0.788, p = 0.014). Sleep difficulties were associated with stereotyped behaviors and parent-perceived stress. Parents interviewed about the gastroenterology visit perceived this multidisciplinary approach as helpful in addressing food selectivity. This study shows that sleep and mealtime issues can have a synergistic negative impact on ASD symptoms. A multidisciplinary approach and an integrated assessment of GI, feeding problems, and sleep disorders could be helpful in diagnosing comorbidities and to provide targeted advice to parents.

Unarousable child with a short bowel

Unarousable child with short bowelA 4-year-old boy was admitted with progressive lethargy of a few hours' duration and no other symptoms. His medical history was relevant for short bowel syndrome (SBS), following neonatal volvulus, with residual bowel length of 23 cm and intact ileocecal valve. He had similar self-limiting episodes in the past, after weaning parenteral nutrition, especially after eating large meals. The day before, he had consumed a large amount of apples.Arterial blood gas (ABG) analysis showed metabolic acidosis with normal lactacidaemia (pH 7.09, pCO2 19 mm Hg, pO2 101 mm Hg, HCO3 5.8 mmol/L, BE -24, anion gap 29.4, chloride 116 mmol/L, L-lactate level 4 mmol/L).On admission, the child could be awakened, but he was confused with slurred speech (Glasgow Coma Scale 14), with a body temperature of 37 C°, a heart rate of 125 beats/min and a respiratory rate of 38 breaths/min. The abdomen was distended, without guarding and with normal bowel sounds. Blood glucose levels were normal, as well as white blood cell count, liver and kidney function test and C reactive protein. An abdominal ultrasound ruled out an intussusception. An abdominal X-ray was performed too (see figure 1).

Chronic Intestinal Failure in Children: An International Multicenter Cross-Sectional Survey

Background: The European Society for Clinical Nutrition and Metabolism database for chronic intestinal failure (CIF) was analyzed to investigate factors associated with nutritional status and the intravenous supplementation (IVS) dependency in children. Methods: Data collected: demographics, CIF mechanism, home parenteral nutrition program, z-scores of weight-for-age (WFA), length or height-for-age (LFA/HFA), and body mass index-for-age (BMI-FA). IVS dependency was calculated as the ratio of daily total IVS energy over estimated resting energy expenditure (%IVSE/REE). Results: Five hundred and fifty-eight patients were included, 57.2% of whom were male. CIF mechanisms at age 1−4 and 14−18 years, respectively: SBS 63.3%, 37.9%; dysmotility or mucosal disease: 36.7%, 62.1%. One-third had WFA and/or LFA/HFA z-scores < −2. One-third had %IVSE/REE > 125%. Multivariate analysis showed that mechanism of CIF was associated with WFA and/or LFA/HFA z-scores (negatively with mucosal disease) and %IVSE/REE (higher for dysmotility and lower in SBS with colon in continuity), while z-scores were negatively associated with %IVSE/REE. Conclusions: The main mechanism of CIF at young age was short bowel syndrome (SBS), whereas most patients facing adulthood had intestinal dysmotility or mucosal disease. One-third were underweight or stunted and had high IVS dependency. Considering that IVS dependency was associated with both CIF mechanisms and nutritional status, IVS dependency is suggested as a potential marker for CIF severity in children.

Young boy with a long history of splenomegaly and cytopenia

A 15-year-old boy was admitted with a history of cytopenia (white blood cell count 3.170/μm, platelets 90.000/μm) associated with splenomegaly, found during investigations for recurrent mild jaundice due to Gilbert's syndrome.He was in good general health, without systemic symptoms; therefore, the leading causes of asymptomatic splenomegaly were excluded. Coagulation, liver tests and abdomen ultrasound (US) were normal, showing a hepatopetal portal flow to the colour-Doppler. There was no sign of haemolysis on haematology investigations. The C reactive protein, immune globulins levels and erythrocyte sedimentation rate were normal, excluding both an infective and an immune regulation disorder. We excluded the haematological malignancy and lymphoproliferative disorders through a peripheral blood smear and a bone marrow biopsy.His history was remarkable for neonatal sepsis, which required umbilical venous catheter during hospitalisation in a neonatal intensive care unit (NICU). The patient follow-up was interrupted for a while, probably due to his good health condition.At age 17 years, the child accessed our emergency department. for a minor trauma to the limbs, and his physical examination was unremarkable, except for the splenomegaly. We repeated the abdomen US, with colour flow Doppler (figure 1).

Ferric Carboxymaltose in the Treatment of Iron-Deficiency Anaemia in Paediatric Patients with Anastomotic Ulcers

Objectives: The aim of this paper is to describe a case series of paediatric patients affected by anastomotic ulcers (AU), a late complication of bowel resection in infancy, focusing on the treatment of iron-deficiency anaemia (IDA) with ferric carboxymaltose (FC). Methods: Patients with a diagnosis of AU, treated at the Paediatric Department of the Institute for Maternal and Child Health IRCCS “Burlo Garofolo” from February 2012 to December 2020 were included. Haemoglobin (Hb) values, IDA related symptoms, the need for blood transfusions, for oral or intravenous (iv) iron supplementation and for surgical resections were compared before and after treatment with FC. Adverse effects of FC were recorded. Results: Ten patients with an established diagnosis of AU were identified; eight (8 out of 10) received at least one administration of FC. Lower and higher Hb values increased significantly after treatment (4.9 g/dL vs. 8.2 g/dL, p = 0.0003; 9.9 g/dL vs. 13.5 g/dL, p = 0.0008 respectively), with a significant reduction of the need for blood transfusions (p = 0.0051) and for oral and iv iron supplementation. While receiving standard therapies, seven patients (7 out of 8) complained of asthenia; this symptom resolved in all cases after FC administration. Before FC treatment, two patients (2 out of 8) required surgical resection of AU, with a recurrence of anaemia after a few weeks; after at least one FC infusion, no children needed further bowel resection for IDA. FC caused mild asymptomatic hypophosphatemia in one case. Conclusion: FC appears to be effective and safe in the paediatric population for the treatment of IDA resulting from AU.

Diagnostic accuracy and applicability of intestinal auto-antibodies in the wide clinical spectrum of coeliac disease

BACKGROUND

Intestinal coeliac auto-antibodies are the marker of coeliac disease (CD). Since the determination of these antibodies is still not widely available, we used immunoassays to identify the most suitable technology for revealing intestinal auto-antibodies in the wide clinical spectrum of CD.

METHODS

Intestinal auto-antibodies have been prospectively investigated in CD suspected children using two immunoassays: intestinal-deposits of IgA anti-tissue transglutaminase antibodies (anti-tTG) and biopsy-culture IgA anti-endomysium (AEA). Intestinal IgM antibodies have been determined in IgA-deficient subjects.

FINDINGS

Two-hundred and twenty-one suspected CD patients were enrolled. Intestinal antibodies were tested positive for both assays in classical CD patients (n = 178) with villous atrophy and positive serum-CD antibodies, potential CD patients (n = 16) with normal intestinal mucosa and positive serum-CD antibodies, and pre-potential CD patients (n = 14) with normal intestinal mucosa and negative serum-CD antibodies. In 13/221 with normal intestinal mucosa, negative CD-serum antibodies and negative intestinal antibodies CD has been excluded. All classical, 14/16 potential and 11/14 pre-potential CD patients on gluten-free diet (GFD) improved their symptoms. In 9/11 pre-potential patients intestinal antibodies disappeared on GFD. Both assays were negative in 69/71 control subjects. The two assays showed high diagnostic sensitivity (100%) and specificity (99%).

INTERPRETATION

Intestinal CD-antibodies make prompt diagnosis in the wide clinical spectrum of CD reducing the delay in diagnosis and treatment, especially in pre-potential CD patients. The easy handling biopsy culture assay is an effective diagnostic tool which should be carried out by any gastroenterology unit to recognize all CD clinical manifestations.

FUNDING

Interreg Central-Europe, IRCCS "Burlo Garofolo".

Severe anaemia after gastric biopsy in an infant with eosinophilic gastritis

Background

Eosinophilic gastrointestinal disorders (EGID) are characterized by eosinophilic inflammation and are subclassified according to the affected site(s) as eosinophilic esophagitis, eosinophilic gastritis, eosinophilic enteritis and eosinophilic colitis. Clinical presentation includes dyspeptic symptoms, vomiting, abdominal pain, diarrhoea and gastrointestinal bleeding. Peripheral eosinophilia is usually found but is not required for the diagnosis. The treatment is based on dietary elimination therapy, consisting of removal of common food triggers, most frequently cow’s milk in infants. Corticosteroids are used as first line drug therapy in EG if dietary therapy fails to achieve an adequate clinical response or is impractical.

Case presentation

A four month old infant was admitted for an episode of melena and hematemesis. An esophagogastroduodenoscopy showed haemorrhagic gastritis with ulcerative lesions and fibrin. A significant gastric bleeding was noted after the procedure. The gastric mucosa biopsies showed an eosinophilic infiltration.

Conclusions

A clinically relevant anaemia is a quite rare complication in infants with eosinophilic gastritis and a biopsy may worsen bleeding, to a potentially severe level of low haemoglobin. In infants with low haemoglobin levels and suspect eosinophilic gastritis a watchful follow up after the biopsy should be considered, as well as the possibility of postponing the biopsy to reduce the bleeding risk.

Immunohistologic analysis of the duodenal bulb: a new method for celiac disease diagnosis in children

BACKGROUND AND AIMS

Anti-tissue transglutaminase antibodies (anti-tTG) have simplified celiac disease (CD) diagnosis. However, in atypical forms of CD, intestinal biopsy sampling is still required. This prospective study investigates whether histologic analysis of the duodenal bulb combined with intestinal IgA anti-tTG deposit immunoassay makes CD diagnosis possible in at-risk children with low concentrations of serum anti-tTG.

METHODS

Histologic and intestinal IgA anti-tTG deposit immunoassays were used.

RESULTS

Two hundred forty-five symptomatic children positive for serum anti-tTG (>7 U/mL) were enrolled and divided into 3 groups: extensive duodenal atrophy (n = 209), with IgA anti-tTG deposits throughout the duodenum and high serum anti-tTG concentrations (157 ± 178 U/mL); bulb duodenal atrophy (n = 22), with widespread IgA anti-tTG deposits in 9 and in the bulb alone in 13 and low serum anti-tTG concentrations (13.9 ± 8.7 U/mL); and normal duodenum (n = 14), with widespread IgA anti-tTG deposits in 8 and in the bulb alone in 6 and low serum anti-tTG concentrations (10.6 ± 6.2 U/mL). All patients in the first 2 groups were diagnosed with CD and 8 from the third group. All improved after 1 year of gluten-free diet. Bulb duodenal analysis led to a 12% (30/245) increase in CD diagnosis. No CD-related lesions were observed in the 30 control subjects.

CONCLUSIONS

In children at risk for CD, bulb duodenum biopsy sampling is essential to identify villous atrophy and detect IgA anti-tTG deposits even in absence of intestinal lesions. These mucosal autoantibodies could well represent a new standard for diagnosing CD.

Rapid anti-transglutaminase assay and patient interview for monitoring dietary compliance in celiac disease

OBJECTIVE

The anti-transglutaminase antibodies (anti-tTG) play an important role in monitoring the celiacs' gluten-free diet (GFD).

MATERIAL AND METHODS

The authors propose to use the rapid IgA anti-tTG assay based on a whole blood drop to evaluate the compliance to GFD at the clinical ambulatory setting. The rapid test results were compared with those of the conventional ELISA assay and with dietary compliance reported by patients' interview.

CONCLUSIONS

The authors showed that anti-tTG rapid test is reliable and easy to perform in the ambulatory setting to evaluate dietary compliance. Moreover, they proved that celiacs' interview is more sensitive than serology in identifying patients who transgress.

Compliance with the gluten-free diet: the role of locus of control in celiac disease

OBJECTIVES

To verify whether subjects with celiac disease (CD) have a different locus of control (LoC) compared with healthy subjects, and to evaluate the relationship between LoC and compliance with a prescribed gluten-free diet (GFD) and quality of life (QoL).

STUDY DESIGN

We studied 156 subjects on a GFD (mean age, 10 years) and 353 healthy controls (mean age, 12 years). All subjects completed tests on the Nowicki-Strickland Locus of Control Scale; the subjects with CD also completed a questionnaire to measure compliance with dietary treatment and the disease's impact on QoL.

RESULTS

There was no difference in LoC values between patients with CD and controls. Subjects with CD with good dietary compliance had a more internal LoC compared with those who were not compliant (P = .01). Patients who reported a satisfactory QoL had a more internal LoC compared with those who reported negative affects on QoL due to CD (P = .01).

CONCLUSIONS

Our study confirms the usefulness of the LoC concept for identifying those patients who might be at risk for dietary transgression. Given the enhanced, psychological, and social well being that can result from adherence to a GFD, educational and psychological support can help internalize the LoC in those patients at risk for dietary transgression.

Bone metabolism in celiac disease

OBJECTIVE

To investigate the prevalence of both calcium metabolism alterations and bone defects in children with celiac disease (CD).

STUDY DESIGN

We studied 54 untreated patients with CD (mean age, 7 years). We compared the serum concentration of calcium, magnesium, 25(OH)vitamin D3, alkaline phosphatase, and parathyroid hormone (PTH) of patients with CD with those of 60 healthy children. Children with CD with 2 laboratory alterations underwent DEXA examination, which was evaluated after 6 months of a gluten-free diet (GFD).

RESULTS

The calcium and the 25(OH)vitamin D3 levels were lower in children with CD than in control subjects, and the PTH level was higher in children with CD than in control subjects (P < .001). Hyperparathyroidism was found in 29 children with CD. Twenty patients tested positive for 2 laboratory alterations, and 10 of them were osteopenic. After 6 months of GFD calcium, 25(OH)vit.D3 and PTH levels normalized, with the improvement of bone mineral density.

CONCLUSIONS

Calcium metabolism defects are common in untreated children with CD, and they returned to normal after GFD. A detailed, time-consuming, and expensive study of bone metabolism is not necessary in children with CD shortly exposed to gluten who follow the GFD.

Looking for celiac disease: diagnostic accuracy of two rapid commercial assays

BACKGROUND

Early diagnosis and treatment with gluten-free diet reduces mortality and the prevalence of associated disorders in celiac disease (CD). A simple "in the office" test of anti-transglutaminase antibodies might be of great help in first-line screening for CD.

AIMS

We evaluated the sensitivity and specificity of two commercial kits based, respectively, on rapid detection of IgA-IgG anti-human-transglutaminase antibodies (anti-h-tTG) in serum and IgA anti-h-tTG antibody in one drop of whole blood. These assays were compared to a well-established enzyme-linked immunosorbent assay technique.

METHODS

Serum samples were analyzed from 114 biopsy-confirmed celiacs, 120 healthy controls, 20 first-degree relatives of celiacs, and 75 diseased controls. The whole blood samples were analyzed from 51 biopsy-confirmed celiacs and 100 controls.

RESULTS

The serum-based test was positive in all 114 celiacs (sensitivity 100%). Among the controls there were seven healthy blood donors, one first-degree relative, and three diseased controls who tested positive (specificity 94.9%). The blood drop-based assay testing IgA antibodies was positive in 46 of 51 (sensitivity 90.2%), and since three of the five patients testing negative had total IgA deficiency, the sensitivity value can be increased to 95.8%. All 100 controls tested negative (specificity 100%).

CONCLUSIONS

The commercial kits described here produce high values of sensitivity and specificity, offering the general practitioner who suspects a possible case of CD the real possibility to look for anti-h-tTG antibodies in his own medical office during a standard visit at a satisfyingly low cost.

PAH gene mutations in the Sicilian population: association with minihaplotypes and expression analysis

The molecular basis of PAH deficiency in the Sicilian population is characterized by a marked heterogeneity, with 44 mutations at a single locus identified by a "gene-scanning" approach and accounting for a detection rate of 91%. The remaining 9% of PAH alleles does not bear mutations in any of the 13 exons and 24 exon/intron junctions. Three mutations IVS10nt-11 G > A, R261Q, and A300S accounted for 30.5%, whereas the remaining mutations were found at relative frequencies of less than 5% and 20 mutations were observed once only. Five mutations have been detected only in Sicilians so far. By studying the association of mutations with intragenic STR-VNTR haplotypes ("minihaplotypes"), "identity by descent" has been established for 24 mutations also detected in other populations. This finding supports the hypothesis of a multipolar origin for a large proportion of PAH mutant alleles currently detected in Sicilians. In order to improve our understanding of the clinical heterogeneity of PAH deficiency in this population, we have for the first time analyzed three missense mutations L41F, T92I, and P211T in vitro by the pCDNA3/COS-7 eukaryotic expression system and found an activity of 10, 76, and 72%, respectively, compared to normal PAH. In two HPA patients with mild PKU and mild hyperphenylalaninemia (MHP), harboring respectively L41F/R261Q and T92I/P281L genotypes, the predicted biochemical effect of these genotypes appeared to be consistent with the metabolic phenotypes. In contrast, discordant metabolic phenotypes (mild PKU and MHP) were observed in two unrelated patients bearing the same R261Q/P211T genotype, a finding which underscores the complex relationship linking genotype to phenotype in PAH deficiency. Hypotheses on the possible mechanisms responsible for the observed discordance are discussed. The spectrum of PAH gene mutations in Sicily reflects the complex demographic history of this island at the crossroad of prehistoric and historical migrations in the Mediterranean sea. The data presented in this study also add to the present knowledge on the relationship between PAH genotypes and HPA phenotype and are expected to improve PAH genotyping among individuals with hyperphenylalaninemia.