Rare clotting in skin’s blood vessels leads to PNH diagnosis: Case report

Extensive clotting in the skin’s small blood vessels, known as dermal thrombosis, was identified in a 44-year-old man who suffered multiple strokes and was later diagnosed with paroxysmal nocturnal hemoglobinuria (PNH), according to a case report from India.

Researchers noted that “prompt recognition of this unusual PNH-related skin thrombosis holds significant value,” given the strong responsiveness of these lesions to anticoagulants combined with complement inhibitors, therapies that target the underlying cause of the disease.

The study, “Dermal thrombosis: an uncommon presentation of Paroxysmal Nocturnal Hemoglobinuria,” was published in the Indian Journal of Hematology and Blood Transfusion.

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Up to 40% of PNH patients develop thrombosis

A blood disorder, PNH is usually caused by acquired mutations in hematopoietic stem cells, the cells that give rise to all blood cells. Such mutations prevent blood cells from producing certain protective proteins on their surface, leaving them vulnerable to attack by the complement system, a part of the body’s immune defenses. This can lead to the destruction of blood cells, particularly red blood cells, and other disease symptoms, including blood-clotting problems.

Up to 40% of people with PNH develop thrombosis, or abnormal blood clots that block blood flow through blood vessels. These clots are the leading cause of severe complications and death in the disease. They usually occur in large veins and arteries, with involvement of the skin’s small blood vessels being uncommon.

In their report, researchers in India described a rare case of dermal thrombosis in a man who was hospitalized after suddenly developing weakness in his left arm, difficulty coordinating his movements, slurred speech, and excessive sweating.

Doctors initially diagnosed the men with a stroke. However, his condition continued to worsen, and further scans revealed additional areas of brain damage caused by interrupted blood flow, along with blockages in major arteries supplying the brain. By the time he was transferred to the researchers’ hospital, his condition had become severe enough that he required a ventilator to help him breathe.

Skin manifestations associated with PNH are uncommon

Nearly a month later, doctors noticed a new and unexpected symptom: multiple purplish skin lesions on his lower legs, feet, and left forearm. Some of these lesions later progressed to skin necrosis, or skin tissue death, and ulcers.

A biopsy of the affected skin revealed extensive dermal thrombosis, meaning widespread clotting within the skin’s small blood vessels. The biopsy also showed a sparse infiltration of neutrophils, a type of immune cell. Unlike vasculitis, an inflammatory condition affecting blood vessels, there was minimal infiltration within the vessel walls themselves. Instead, the mild inflammatory response was seen mainly in the surrounding tissue.

Because the findings suggested an underlying clotting disorder, doctors performed additional tests to determine the cause. Results showed that nearly all patients’ neutrophils and a smaller proportion of monocytes — another type of immune cell — lacked the protective surface proteins typically absent in PNH, confirming a PNH diagnosis.

According to the researchers, “skin manifestations associated with PNH are uncommon” and may appear as small pinpoint spots, blood-filled blisters, ulcers, or areas of skin death, most often affecting the legs and ears. Because several other disorders can produce similar skin findings, an early biopsy can help distinguish PNH-related thrombosis from other causes, allowing timely diagnosis and treatment.