Adult Refsum disease (RD) is a rare autosomal recessive peroxisomal disorder with an estimated prevalence of fewer than 1 in 1 million. The ocular manifestations result from the accumulation of phytanic acid, leading to retinitis pigmentosa, attenuated retinal vessels, bone spicule pigmentation, optic disc pallor, and macular involvement in advanced stages. To date, there has been no documented association between RD and microspherophakia, a rare lens abnormality more commonly linked to Weill-Marchesani syndrome. Microspherophakia is characterized by a small lens diameter, increased anteroposterior thickness, and a visible lens equator upon full mydriasis. We present a unique case of concurrent RD and microspherophakia.

Adult Refsum disease is a rare hereditary peroxisomal disorder characterized by impaired phytanic acid metabolism. The accumulation of phytanic acid in tissues, especially adipose and neural, is believed to contribute to disease manifestations. Clinically apparent kidney dysfunction has been reported in only 2 cases. We describe a 55-year-old woman with adult Refsum disease, who was referred to nephrology for impaired kidney function without proteinuria. Kidney biopsy showed vacuolization of proximal tubular epithelium and unremarkable glomeruli. Focally, distal tubular cytoplasm showed variably sized crystals with ultrastructural laminated substructures (or "paracrystalline formation"). To the best of our knowledge, the light microscopy for these crystals in a peroxisomal disease has not been previously described, and adult Refsum disease has not been described as a significant metabolic kidney disorder. These unique morphologic features contribute to the spectrum of findings in this rare genetic condition. This case also demonstrates the value of kidney function monitoring and therapeutic plasma exchange for these patients.

Retinitis pigmentosa (RP) is a progressive inherited retinal dystrophy, characterized by the degeneration of photoreceptors, presenting as a rod-cone dystrophy. Approximately 20-30% of patients with RP also exhibit extra-ocular manifestations in the context of a syndrome. This manuscript discusses the broad spectrum of syndromes associated with RP, pathogenic mechanisms, clinical manifestations, differential diagnoses, clinical management approaches, and future perspectives. Given the diverse clinical and genetic landscape of syndromic RP, the diagnosis may be challenging. However, an accurate and timely diagnosis is essential for optimal clinical management, prognostication, and potential treatment. Broadly, the syndromes associated with RP can be categorized into ciliopathies, inherited metabolic disorders, mitochondrial disorders, and miscellaneous syndromes. Among the ciliopathies associated with RP, Usher syndrome and Bardet-Biedl syndrome are the most well-known. Less common ciliopathies include Cohen syndrome, Joubert syndrome, cranioectodermal dysplasia, asphyxiating thoracic dystrophy, Mainzer-Saldino syndrome, and RHYNS syndrome. Several inherited metabolic disorders can present with RP, including Zellweger spectrum disorders, adult Refsum disease, α-methylacyl-CoA racemase deficiency, certain mucopolysaccharidoses, ataxia with vitamin E deficiency, abetalipoproteinemia, several neuronal ceroid lipofuscinoses, mevalonic aciduria, PKAN/HARP syndrome, PHARC syndrome, and methylmalonic acidaemia with homocystinuria type cobalamin (cbl) C disease. Due to the mitochondria's essential role in supplying continuous energy to the retina, disruption of mitochondrial function can lead to RP, as seen in Kearns-Sayre syndrome, NARP syndrome, primary coenzyme Q10 deficiency, SSBP1-associated disease, and long chain 3-hydroxyacyl-CoA dehydrogenase deficiency. Lastly, Cockayne syndrome and PERCHING syndrome can present with RP, but they do not fit the abovementioned hierarchy and are thus categorized as miscellaneous. Several first-in-human clinical trials are underway or in preparation for some of these syndromic forms of RP.

Refsum disease is a rare autosomal recessive hereditary disorder of lipid metabolism that results in the accumulation of phytanic acid. This syndrome is characterized with a range of classic symptoms including ataxia, peripheral neuropathy, amyotrophy, retinopathy, ichthyosis, and hearing loss. Later in life, individuals with Refsum disease may present cardiac manifestations, such as arrhythmias or conduction defects (first-degree atrioventricular block and bundle branch block) and hypertrophic or dilated cardiomyopathy, leading to heart failure and sudden death. To the best of our knowledge, this is the first case revealed by cardiac manifestations described in literature. We report the case of 38-year-old white Moroccan male who was admitted in our department for an acute decompensated heart failure episode. Transthoracic echocardiography found a dilated cardiomyopathy with a reduced ejection fraction at 15%. Further evaluation showed different features of Refsum disease. High plasma level of phytanic acid confirmed the diagnosis. Cardiac manifestations are frequent in the late course of the adult Refsum disease and include, cardiomyopathy, electrical abnormalities, and sudden cardiac death. Moreover, arrhythmias remain one of the main causes of death in these patients. Refsum's disease is an autosomal recessive disorder. It presents as retinitis pigmentosa with anosmia, deafness ataxia, and cardiac defects. Current interventions for individuals with Refsum disease consist of dietary phytanic acid restriction and lipid apheresis to control symptoms and enhance quality of life. What is now known as Refsum disease was initially described by Sigvald Refsum as heredoataxia hemeralopica polyneuritiformis in 1945, but its name was changed to heredopathia atactica polyneuritiformis the following year. Today, Refsum disease is synonymous with "adult Refsum disease" and "classic Refsum disease." The Online Catalog of Human Genes and Genetic Disorders (OMIM) records adult Refsum disease as phenotype MIM number #266500. The condition is rare, autosomal recessive, and classified as a disorder of peroxisomal function.  Peroxisomes are single membrane-bound intracellular organelles that generate peroxide for use in metabolic functions. Their functions are far-reaching and include a vast complement of lipid catabolism and biogenesis functions; the dysfunction in lipid catabolism is responsible for Refsum disease. The fundamental characteristic of disorders of peroxisome function is that they are due to a deficiency in the function of a single enzyme. This produces specific metabolic abnormalities. Refsum disease is caused by a deficiency of the phytanoyl-CoA hydroxylase, which results in deficient catabolism of phytanic acid and an excess. The core of Refsum disease's clinical characteristics is due to the effects of phytanic acid buildup on the nervous system. Since the terminology surrounding Refsum disease can be confusing, it is worth emphasizing that Refsum disease is distinct from infantile Refsum disease, which falls within the Zellweger spectrum disorders. These are classified as disorders of peroxisomal biogenesis and assembly. For more information on infantile Refsum disease, see StatPearls' companion topic, "Zellweger Spectrum Disorder."

Patients with adult Refsum Disease (ARD) have retinitis pigmentosa and thus nyctalopia, anosmia, sensorineural deafness, polyneuropathy, and ataxia. Upon physical examination, patients with ARD have congenital short metacarpals, metatarsals, and cardiac arrhythmias. Manifestations due to the lack of phytanoyl-CoA hydroxylase in peroxisomes needed for alpha-oxidation of phytanic acid lead patients to accumulate phytanic acid in their body tissues. To our knowledge, no consensus for clinical diagnostic criteria for patients with ARD has been published. Our patient had nyctalopia, retinal findings, and visual field results compatible with retinitis pigmentosa. Additionally, the patient had decreased macular thickness and volume in both eyes, the findings being worse in the left eye. The patient had undergone hand surgery due to chronic pain in both hands, as well as his fourth and fifth metatarsal bones were shortened. Interestingly, audiology evaluation showed mild hearing loss in the right ear and mild to moderate hearing loss in the left ear. Inheritance patterns in patients with ARD have been described. Physical examination, phytanic acid evaluation, and genetic studies may all help reach an ARD diagnosis. This is the first report of adult Refsum disease in Puerto Rico.