Discriminative Features in Three Autosomal Recessive Cutis Laxa Syndromes: Cutis Laxa IIA, Cutis Laxa IIB, and Geroderma Osteoplastica

Cutis laxa is a heterogeneous condition characterized by redundant, sagging, inelastic, and wrinkled skin. The inherited forms of this disease are rare and can have autosomal dominant, autosomal recessive, or X-linked inheritance. Three of the autosomal recessive cutis laxa syndromes, namely cutis laxa IIA (ARCL2A), cutis laxa IIB (ARCL2B), and geroderma osteodysplastica (GO), have very similar clinical features, complicating accurate diagnosis. Individuals with these conditions often present with cutis laxa, progeroid features, and hyperextensible joints. These conditions also share additional features, such as short stature, hypotonia, and congenital hip dislocation, but the severity and frequency of these findings are variable in each of these cutis laxa syndromes. The characteristic features for ARCL2A are abnormal isoelectric focusing and facial features, including downslanting palpebral fissures and a long philtrum. Rather, the clinical phenotype of ARCL2B includes severe wrinkling of the dorsum of the hands and feet, wormian bones, athetoid movements, lipodystrophy, cataract and corneal clouding, a thin triangular face, and a pinched nose. Normal cognition and osteopenia leading to pathological fractures, maxillary hypoplasia, and oblique furrowing from the outer canthus to the lateral border of the supraorbital ridge are discriminative features for GO. Here we present 10 Iranian patients who were initially diagnosed clinically using the respective features of each cutis laxa syndrome. Each patient’s clinical diagnosis was then confirmed with molecular investigation of the responsible gene. Review of the clinical features from the cases reported from the literature also supports our conclusions.


Patients
An in depth clinical evaluation, with documentation of phenotypic features, was completed for each patient. Detailed clinical data was obtained by a standardized questionnaire. All families provided written informed consent according to institutional guidelines. Ethics approval was obtained by the Kariminejad-Najmabadi Pathology and Genetics Center ethical committee.
The observed characteristics and symptoms were then compared against the discriminative features of each cutis laxa syndrome to preliminarily diagnose each patient. The clinical diagnoses indicated which genes needed to investigated by Sanger sequencing in each case. In all cases the candidate genes suggested by the clinical phenotype were then confirmed by molecular investigation.
Here we report 10 patients with ARCL2A, ARCL2B, or geroderma osteodysplastic (GO) and discuss the clinical features that help differentiate between these three cutis laxa syndromes. The clinical findings from each patient are reported in Table 1. Table 2 is a comparison of the frequency of the clinical features observed in ARCL2A, ARCL2B, and GO as reported in the literature against the frequency in our cases (Tables A1-A3).

Discussion
Although there is a large phenotypic overlap among the three types of cutis laxa syndromes, ARCL2A, ARCL2B, and GO, in this manuscript we highlight the main differences that allow for clinical discrimination amongst them.

Overlapping Features
Cutis laxa, progeroid features, hyperextensible joints, inelastic wrinkled skin, and flat feet are features found in all three cutis laxa syndromes (Figure 1a-o) ( Table 2). All of our patients, regardless of the cutis laxa syndrome, demonstrated flat feet however the frequency of feature has not been reported in the literature. Hypotonia and congenital hip dislocation are also found in all three conditions, but the severity and frequency of these findings varies. Short stature and open fontanel are common findings in cutis laxa types 2A and 2B, but occur less frequently in GO (Table 2); however, in our patients 3 4 showed short stature. Osteopenia is characteristic of both ARCL2B and GO, though it is much more severe in GO and may even lead to pathologic fractures, especially of the vertebral column. We cannot comment on osteopenia in ARCL2A as it was not evaluated in the cases reported in the literature.

Discussion
Although there is a large phenotypic overlap among the three types of cutis laxa syndromes, ARCL2A, ARCL2B, and GO, in this manuscript we highlight the main differences that allow for clinical discrimination amongst them.

Overlapping Features
Cutis laxa, progeroid features, hyperextensible joints, inelastic wrinkled skin, and flat feet are features found in all three cutis laxa syndromes (Figure 1a-o) ( Table 2). All of our patients, regardless of the cutis laxa syndrome, demonstrated flat feet however the frequency of feature has not been reported in the literature. Hypotonia and congenital hip dislocation are also found in all three conditions, but the severity and frequency of these findings varies. Short stature and open fontanel are common findings in cutis laxa types 2A and 2B, but occur less frequently in GO (Table  2); however, in our patients ¾ showed short stature. Osteopenia is characteristic of both ARCL2B and GO, though it is much more severe in GO and may even lead to pathologic fractures, especially of the vertebral column. We cannot comment on osteopenia in ARCL2A as it was not evaluated in the cases reported in the literature.

Facial Features
Each of the cutis laxa syndromes has distinct facial features. The ARCL2A patients demonstrate frontal bossing, large open fontanels, reverse V eyebrows, downslanting palpebral fissures, strabismus, a long philtrum and sagging cheeks with anteverted nares. The downslanting palpebral fissures and long philtrum are particularly indicative of ARCL2A and may help in establishing the diagnosis. The ARCL2B patients present during infancy and childhood with thin triangular faces, broad foreheads, a thin nose, and thin skin. Patients with this syndrome usually lack the sagging cheeks commonly seen in infants with ARCL2A and GO (Figure 2b). Though there are only a few adults with ARCL2B reported in the literature, the evidence supports that in adulthood, this face is no longer triangular but, rather, becomes long, with a prominent chin [15,17] (Figure 2c). Patient with GO demonstrate maxillary hypoplasia, sagging cheeks, and oblique furrowing, which extends from the outer canthus to the lateral border of the supraorbital ridge. This characteristic is generally more prominent in infancy and childhood (Figure 2g,h).

Facial Features
Each of the cutis laxa syndromes has distinct facial features. The ARCL2A patients demonstrate frontal bossing, large open fontanels, reverse V eyebrows, downslanting palpebral fissures, strabismus, a long philtrum and sagging cheeks with anteverted nares. The downslanting palpebral fissures and long philtrum are particularly indicative of ARCL2A and may help in establishing the diagnosis. The ARCL2B patients present during infancy and childhood with thin triangular faces, broad foreheads, a thin nose, and thin skin. Patients with this syndrome usually lack the sagging cheeks commonly seen in infants with ARCL2A and GO (Figure 2b). Though there are only a few adults with ARCL2B reported in the literature, the evidence supports that in adulthood, this face is no longer triangular but, rather, becomes long, with a prominent chin [15,17] (Figure 2c). Patient with GO demonstrate maxillary hypoplasia, sagging cheeks, and oblique furrowing, which extends from the outer canthus to the lateral border of the supraorbital ridge. This characteristic is generally more prominent in infancy and childhood (Figure 2g,h).

Progeroid Features
Clinical findings vary as the children with these cutis laxa syndromes grow older. At birth, the ARCL2B patients are usually very small with many having intrauterine growth retardation. The adult ARCL2B patient, however, is not particularly short but usually has a low weight and exhibits lipodystrophy (Figure 2c). ARCL2B infants have very thin skin, visible veins over thorax and clenched hands, but these symptoms improve considerably as the patient grows older (Figure 2d-f). Infants with GO usually have normal birth weights and lengths. The progeroid features improve in the majority of patients as the child grows older and reaches adult age. This progression is most

Progeroid Features
Clinical findings vary as the children with these cutis laxa syndromes grow older. At birth, the ARCL2B patients are usually very small with many having intrauterine growth retardation. The adult ARCL2B patient, however, is not particularly short but usually has a low weight and exhibits lipodystrophy (Figure 2c). ARCL2B infants have very thin skin, visible veins over thorax and clenched hands, but these symptoms improve considerably as the patient grows older (Figure 2d-f). Infants with GO usually have normal birth weights and lengths. The progeroid features improve in the majority of patients as the child grows older and reaches adult age. This progression is most obvious in ARCL2A (Figure 2a) [5,7,17]. Contrary to the improvement in the progeroid features, the abnormal fat distribution seen in ARCL2A worsens with age (Figure 3a-c) [4]. obvious in ARCL2A (Figure 2a) [5,7,17]. Contrary to the improvement in the progeroid features, the abnormal fat distribution seen in ARCL2A worsens with age (Figure 3a-c) [4].
Based on the patients examined in this study, it seems that joint hyperlaxity improves as the patients reach adulthood. Hyperlaxity was seen in all of our child and infant cases, but of the three adult cases reported in this manuscript (two ARCL2B patients and one GO patient), all had very mild to absent joint hyperlaxity.

Neurological Features
The neurological findings common to ARCL2A and ARCL2B patients are intellectual disability, hypotonia, psychomotor retardation, microcephaly, and seizures. Patients with GO, however, only demonstrate hypotonia if they demonstrate any neurological findings at all. Brain MRI imaging would be expected to differentiate between ARCL2A and ARCL2B based on the presence of cobblestone dysgenesis in ARCL2A compared to dysgenesis or agenesis of corpus callosum in cutis laxa IIB ( Figure 4A-H) [2,5]. Brain MRI was not performed as part of this study and these features were not evaluated in our reported patients. Additionally, athetoid movements can occasionally be seen in ARCL2B and hearing loss has been reported in ARCL2A.
Microcephaly may be congenital or may develop during the course of the disease in ARCL2A [5]. Intellectual disability has been reported in ARCL2B but with the following exceptions: one large family with a complete deletion of PYCR1 gene [16], in another patient with the c.138+1G>A mutation [2], and in three patients with missense alterations not residing in exons 4 to 6 [17]. The frequency of intellectual disability in ARCL2A is 78% based on all the reported cases in the literature. Almost all of the patients with GO that have been reported in the literature have normal cognition (94%). Based on the patients examined in this study, it seems that joint hyperlaxity improves as the patients reach adulthood. Hyperlaxity was seen in all of our child and infant cases, but of the three adult cases reported in this manuscript (two ARCL2B patients and one GO patient), all had very mild to absent joint hyperlaxity.

Neurological Features
The neurological findings common to ARCL2A and ARCL2B patients are intellectual disability, hypotonia, psychomotor retardation, microcephaly, and seizures. Patients with GO, however, only demonstrate hypotonia if they demonstrate any neurological findings at all. Brain MRI imaging would be expected to differentiate between ARCL2A and ARCL2B based on the presence of cobblestone dysgenesis in ARCL2A compared to dysgenesis or agenesis of corpus callosum in cutis laxa IIB ( Figure 4A-H) [2,5]. Brain MRI was not performed as part of this study and these features were not evaluated in our reported patients. Additionally, athetoid movements can occasionally be seen in ARCL2B and hearing loss has been reported in ARCL2A.
Microcephaly may be congenital or may develop during the course of the disease in ARCL2A [5]. Intellectual disability has been reported in ARCL2B but with the following exceptions: one large family with a complete deletion of PYCR1 gene [16], in another patient with the c.138+1G>A mutation [2], and in three patients with missense alterations not residing in exons 4 to 6 [17]. The frequency of intellectual disability in ARCL2A is 78% based on all the reported cases in the literature. Almost all of the patients with GO that have been reported in the literature have normal cognition (94%).

Discriminative Features in ARCL2A
The features unique to patients with ARCL2A are abnormal isoelectric focusing, downslanting palpebral fissures, and a long philtrum.

Discriminative Features in ARCL2B
Facial features specific for ARCL2B are a thin triangular face with pinched nose in infancy and childhood that progresses to a long face with a prominent chin in adulthood. Severe wrinkling of the dorsum of the hands and feet is also more prominent in ARCL2B compared to ARCL2A and GO. Though not seen in all patients with cutis laxa IIB, wormian bones, athetoid movements, lipodystrophy, cataracts and corneal clouding are highly specific for ARCL2B. These features are either not seen or very rarely seen in the other two cutis laxa syndromes [17].

Discriminative Features in GO
Patients with GO have normal mentation, whereas the majority of the patients with ARCL2A and ARCL2B have variable degrees of intellectual disability. While patients with ARCL2B may manifest osteopenia, osteopenia that is severe enough to cause pathologic fractures is more characteristic of GO. Facial features specific to GO are maxillary hypoplasia and oblique furrowing from the outer canthus to the lateral border of the supraorbital ridge.

Conclusions
In conclusion, we believe that in spite of great similarity in ARCL2A, ARCL2B, and GO syndromes, there are discriminative features unique to each condition that can guide accurate clinical diagnosis of cutis laxa syndrome subtypes, so that we were able to correctly make the clinical diagnosis. Sanger sequencing of the candidate gene would be much more cost effective to the general approach of next-generation sequencing cutis laxa panels.

Acknowledgments:
The authors are thankful to Therese E. Gadomski for her critical review of the manuscript.

Conflicts of Interest:
The authors declare no conflict of interest.

Discriminative Features in ARCL2A
The features unique to patients with ARCL2A are abnormal isoelectric focusing, downslanting palpebral fissures, and a long philtrum.

Discriminative Features in ARCL2B
Facial features specific for ARCL2B are a thin triangular face with pinched nose in infancy and childhood that progresses to a long face with a prominent chin in adulthood. Severe wrinkling of the dorsum of the hands and feet is also more prominent in ARCL2B compared to ARCL2A and GO. Though not seen in all patients with cutis laxa IIB, wormian bones, athetoid movements, lipodystrophy, cataracts and corneal clouding are highly specific for ARCL2B. These features are either not seen or very rarely seen in the other two cutis laxa syndromes [17].

Discriminative Features in GO
Patients with GO have normal mentation, whereas the majority of the patients with ARCL2A and ARCL2B have variable degrees of intellectual disability. While patients with ARCL2B may manifest osteopenia, osteopenia that is severe enough to cause pathologic fractures is more characteristic of GO. Facial features specific to GO are maxillary hypoplasia and oblique furrowing from the outer canthus to the lateral border of the supraorbital ridge.

Conclusions
In conclusion, we believe that in spite of great similarity in ARCL2A, ARCL2B, and GO syndromes, there are discriminative features unique to each condition that can guide accurate clinical diagnosis of cutis laxa syndrome subtypes, so that we were able to correctly make the clinical diagnosis. Sanger sequencing of the candidate gene would be much more cost effective to the general approach of next-generation sequencing cutis laxa panels.